How Does Light Intensity Affect The Rate Of Photosynthesis

If there is no light, there will be no photosynthesis. As light intensity increases, the rate of photosynthesis will increase as long as other factors are in adequate supply. As the rate increases, eventually another factor will come into short supply.

Why does light intensity increase the rate of photosynthesis?

The Rate of Photosynthesis – The four key factors affecting the rate of photosynthesis are:

Chlorophyll concentration – High chlorophyll concentration gives a high rate of photosynthesis. Light intensity – Increasing light intensity increases the rate of photosynthesis because more energy is provided. However, if the light intensity is increased above a certain threshold, the rate of photosynthesis will not increase because another factor (such as temperature) is limiting the rate of the reaction. Carbon dioxide concentration – Increasing the carbon dioxide concentration increases the rate of photosynthesis because carbon dioxide is a reactant in photosynthesis. However, above a certain threshold, further increases in the carbon dioxide concentration do not increase the rate of photosynthesis because another factor (such as light intensity) is limiting the rate of reaction. Temperature – Increasing the temperature increases the rate of photosynthesis because more energy is provided. However, if the temperature is increased to above about 45°C, the enzymes that catalyse (speed-up) the reaction begin to denature (not work anymore). This causes the rate of the reaction to drop sharply until it stops altogether.

Initially, increasing temperature increases the rate of photosynthesis, as more energy is provided. Above a certain temperature (about 45 degrees Celsius), the enzymes involved in the reaction begin to denature and, consequently, the rate of the reaction begins to drop sharply until it stops altogether.

How does decreasing light intensity affect the rate of photosynthesis?

Too high or too low PAR intensities adversely affect the photosynthetic machinery. At low light intensities above the light compensation point (LCP), photosynthetic rate increases proportionally to the light intensity and reaches a maximum.

How does light intensity affect plant growth?

Light, Temperature and Humidity – Ornamental Production Ornamental Production Light is an essential factor in maintaining plants. The rate of growth and length of time a plant remains active is dependent on the amount of light it receives. Light energy is used in photosynthesis, the plant’s most basic metabolic process.

When determining the effect of light on plant growth there are three areas to consider: intensity, duration and quality. Light Intensity Light intensity influences the manufacture of plant food, stem length, leaf color and flowering. Generally speaking, plants grown in low light tend to be spindly with light green leaves.

A similar plant grown in very bright light tends to be shorter, better branches, and have larger, dark green leaves. Light exposure Plants can be classified according to their light needs, such as high, medium and low light requirements. The light intensity received by an indoor plant depends upon the nearness of the light source to the plant.

Light intensity rapidly decreases as the distance from the light source increases. Window direction in a home or office affects the intensity of natural sunlight that plants receive. Southern exposures have the most intense light. Eastern and western exposures receive about 60 percent of the intensity of southern exposures, while northern exposures receive 20 percent of the intensity of a southern exposure.

A southern exposure is the warmest, eastern and western are less warm, and a northern exposure is the coolest. Other factors such as curtains, trees outside the window, weather, season of the year, shade from other buildings and window cleanliness also effect light intensity.

Reflective, light-colored surfaces inside a home or office tend to increase light intensity, while dark surfaces decrease light intensity. Directional Exposure: Day and Night: Day length or duration of light received by plants is also of some importance. Poinsettias, kalanchoes and Christmas cactus flower only when days are 11 hours or less (short-day plants).

Some plants only flower when days are longer than 11 hours (long-day plants), while others are not sensitive to day length at all (day-neutral plants). Day Length: Increasing the time (duration) plants are exposed to light can be used to compensate for low light intensity, as long as the plant’s flowering cycle is not sensitive to day length.

• Increased light duration allows the plant to make sufficient food to survive and grow.
• However, plants require some period of darkness to properly develop and should be exposed to light for no more than 16 hours per day.
• Excessive light is as harmful as too little.
• When a plant gets too much direct light, the leaves become pale, sometimes burn, turn brown and die.

Therefore, protect plants from too much direct sunlight during summer months. Supplemental Light: Additional lighting can be supplied with either incandescent or fluorescent lights. Incandescent lights produce a great deal of heat and do not use electricity very efficiently.

If artificial light is the only source of light for growing plants, the quality of light or wavelength, must be considered. Plants require mostly blue and red light for photosynthesis, but for flowering, infrared light is also needed. Incandescent lights produce mostly red and some infrared light, but very little blue light.

Fluorescent lights vary according to the amount of phosphorus used by the manufacturer. Cool-white lights produce mostly blue light and are low in red light; they are cool enough to position quite close to plants. Foliage plants grow well under cool-white fluorescent lights, while blooming plants require extra infrared light.

1. This can be supplied by incandescent lights or special horticultural fluorescent lights.
2. Temperature Most plants tolerate normal temperature fluctuations.
3. In general, foliage plants grow best between 70 degrees and 80 degrees F.
4. During the day and between 60 degrees to 68 degrees F. at night.
5. Most flowering plants prefer the same daytime temperature range, but grow best when nighttime temperatures range from 55 degrees to 60 degrees F.

Lower nighttime temperatures help the plant: recover from moisture loss, intensify flower color and prolong flower life. Excessively low or high temperatures may cause: plant stress, inhibit growth, or promote a spindly appearance and foliage damage or drop.

1. Cool nighttime temperatures are actually more desirable for plant growth than high temperatures.
2. A good rule of thumb is to keep nighttime temperatures 10 to 15 degrees lower than daytime temperatures.
3. Misting: Atmospheric humidity is expressed as the percentage of moisture to air.This is important to plants in modifying moisture loss and temperatures.

There are several ways to increase relative humidity around plants. A humidifier can be attached to the heating or ventilating system in the home or office. Also, gravel trays with a constant moisture level can be placed under pots or containers. As the moisture around the pebbles evaporates, the relative humidity in the vicinity of the plants is increased.

1. Humidity Another means of raising humidity is to group plants close together.
2. Misting the foliage of plants is not generally recommended because of the increased potential for spreading diseases.
3. If a mist is used, it should be applied early in the day so that leaves will dry before the onset of cooler nighttime temperatures.

For details on specific light & temperature requirements see : Light, Temperature and Humidity – Ornamental Production Ornamental Production

Why does blue light increase the rate of photosynthesis?

4.68.5.3.2 Blue Light – Blue light plays an important role in most plant functions. Blue light is highly absorbed by both chlorophyll a and b, as well as an intact leaf system. This high absorption rate corresponds to the photosynthetic action spectrum from isolated chloroplasts and intact leaves.6 The photosynthetic response to blue light is highly variable among species and can change within a species depending on amount of blue within a spectrum.7 Species such as cucumber, radish, pepper, and lettuce have shown increases in photosynthetic rates when grown under a red-blue light mixture compared to a sole red light spectrum.7 Under 350 μmol m −2 s −1 of light, an increase in the photosynthetic rate of wheat is observed when as little as 1% of the light spectrum was blue and a further increase is observed with a 10% blue light component.8 However, in some species such as tomato and soybean an increase in blue light was shown to have similar photosynthetic rates as a sole red light spectrum.7 While research pertaining to the role of blue light in the photosynthetic process has been ongoing for decades, the effects are still debatable among species.

Stomatal function also influences the rate of photosynthesis as stomata are the portal in which H 2 O and CO 2 exchange between the leaf and the atmosphere. The effect on stomatal function is one of the most studied processes regulated by blue light. In both isolated stomatal guard cells and intact leaf tissue, irradiation with even low levels of blue light induces stomatal opening.

As determined via the use of mutated Arabidopsis plants, the blue light mediated stomatal opening is in response to the absorption of blue photons by the blue light photoreceptors, phototropin 1 and 2 (phot1 and phot2).9 The absorption of blue light by phot1 and phot2 initiates H + efflux from the guard cell, causing a hyperpolarization leading to K + ion influx and ultimately stomatal opening.9 The increase in stomata aperture will result in higher water loss via transpiration from the leaf.

1. An increase in stomatal opening may also be the explanation for the increase in photosynthetic rate discussed above as this will facilitate more CO 2 influx into the leaf.
2. While the response of the photosynthetic machinery and stomatal operation are direct effects of blue light in the sense that they happen within seconds of exposure, blue light can also have profound indirect effects on plant and leaf morphology.

As the blue light component increased, the plant height of tomato, radish, soybean, and pepper decreased compared to plants grown under sole red light.7,10 These results are consistent with the effects of CRY on hypocotyl growth inhibition of plants grown under blue light.

The decrease in overall plant height also correlates to a decrease in shoot dry mass as blue light increased.10 However, in cucumber, when grown under a sole blue LED, the plant height is increased compared to a plant grown under sole red light. This is inconsistent with the general trend mentioned above and contrary to hypocotyl inhibition due to CRY absorption of blue light.10 Growth under sole blue light may cause morphological effects which do not follow typical alterations associated with increasing blue light when it is part of a broader light spectrum.

The addition of blue light to a light spectrum has been shown to increase the leaf area of peppers, cucumbers, and lettuce compared to plants grown under red or broad light spectrum.10–13 However, it has been observed that in cucumbers an increase in leaf area is only observed during growth under a spectrum which contains 10% blue light.10 The leaf expansion response induced by blue light has been attributed to phot1 as genetic knockout of the photoreceptor inhibits leaf expansion in Arabidopsis,14 It is thought that like the response of stomata to blue light, blue light-induced leaf expansion is done in order to increase the plants’ ability to capture light and ultimately increase photosynthesis.

It should be noted that tomato does not show an increase in leaf area when exposed to blue light or blue light-enriched growth spectrum.15,16 Even without the increase in leaf area in tomatoes, there is still a significant increase in photosynthetic capacity from leaves grown under red and blue LEDs compared to leaves grown under solely red or blue LEDs.15 The addition of a secondary, or even tertiary wavelength, in low amounts to a growth spectrum can provide plants with much better growing conditions to help optimize growth than sole wavelength lighting alone.

Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780444640468004687

Does photosynthesis takes place only in high intensity of light?

Instant Solution: Step 1/6 Step 1: First, we need to understand what photosynthesis is. Photosynthesis is a process used by plants and other organisms to convert light energy, usually from the Sun, into chemical energy that can be later released to fuel the organisms’ activities.

1. Step 2/6 Step 2: Next, we need to understand the conditions under which photosynthesis takes place.
2. Photosynthesis requires light energy, carbon dioxide, and water.
3. The light energy is used to break down water and carbon dioxide molecules.
4. Step 3/6 Step 3: Now, we need to consider the options given in the question.

The first option states that photosynthesis takes place only in sunlight. This is true because sunlight provides the light energy required for photosynthesis. Video by Hafiza Rehmat Numerade Educator

How does light intensity affect the rate of photosynthesis quizlet?

Increasing light intensity increases the photosynthetic rate until a certain point in reached and the rate of photosynthesis levels off. This is because the plant is unable to absorb carbon dioxide fast enough. Only small fractions of the water plants absorb are needed for photosynthesis.

Why does too much light decrease photosynthesis?

Dealing With the Hazards of Harnessing Sunlight Sunlight is the ultimate energy source for virtually all life on Earth. This energy is harnessed by primary producers, organisms capable of using solar energy in photosynthesis, to create energy-rich sugars and sugar-derived molecules as the basis of the Earth’s supply of food, fuels, and materials like wood and cotton.

1. Photosynthetic organisms are also the source of all free oxygen, a molecule essential to almost all life.
2. Primary producers come in all forms and sizes, from photosynthetic microbes to giant algae and plants, and populate both oceans and land.
3. Harnessing solar energy, however, is hazardous, and presents a formidable challenge to photosynthetic organisms.

In fact, un-utilized light energy (any energy not converted to stable products like sugars) has the potential to destroy the light-collecting system itself. Moreover, such un-utilized energy can also destroy other major cell components and swiftly kill the whole cell.

How? In photosynthesis, a light-absorbing pigment (typically chlorophyll) becomes energized after absorbing a photon of light (Figure 1). This energized state is what ultimately supplies the energy for the synthesis of energy-rich sugars. However, when more light is absorbed than can be utilized for sugar production, the (un-utilized, or excess) excitation energy can instead be passed off to oxygen.

The resulting highly reactive oxygen has the potential to destroy the photosynthetic system and lead to cell death. Photosynthesis as we know it could therefore not exist (in an oxygen-containing atmosphere) without powerful photo-protective mechanisms, protecting against potential damage by un-utilized light energy. Figure 1: Scheme of photoprotection mechanisms. Photoprotection occurs via several different mechanisms, often acting in concert with one another: Avoidance, Photorespiration, Dissipation, and Anti-oxidation. Light energy can be physically avoided by cutting down on light absorption.

How do light intensity and CO2 affect photosynthesis?

Light provides the energy for photosynthetic pig- ments to convert carbon dioxide (CO2) and water into sugars and oxygen. As light intensity increases – until a point – the amount of sugars increases and thus, more energy is available for plant growth and maintenance.

Do plants grow faster with higher light intensity?

How does light intensity affect plant growth?

Asked February 17, 2014, 5:16 AM EST How does light intensity affect plant growth? County Outside United States

This is a rather strange question and it can not be answered in a short comment that is normally done in this system! Such questions are often from young students looking for answers that have come from their teachers, and we are not in the business of doing your studying! There are dozens of books written on the influence of light quality and intensisty on the physiology and growth of plants.

These are in libraries and many are also available online!Each plant group reacts differently and has different physiology to deal with light intensity. Some plants do well in low light intensity and would be “burned” with high intensity light while other plants can only do well in full sunlight for long periods of time.

If these are put into low light, the slow their growth and eventually die.With that said, plants generally use light to perform the process of photosynthesis which uses the light energy to combine CO2 with water to make sugars and 02. The higher the light intensity, the more rapid this process can proceed.

1. Thus, most plants grow faster in higher light intensities.
2. Many plants actually will appear lighter green in high light intensity because the chlorophyll in the cells is sufficient to make all the sugar that the plant needs.
3. These same plants may appear darker green in low light intensity because they need more chlorophyll to make the same amount of sugar in low light.

Also, in general, in high light intensities, leaves will be smaller and the internodal distance (distance between where leaves and branches emerge) will be shortened.By searching the internet using “plant growth light intensity” as the search words, I come up with hundreds of web sites that more thoroughly discuss this topic.

What light intensity is best for photosynthesis?

What Are the Best Light Sources For Photosynthesis? Photosynthetic organisms such as plants and algae use electromagnetic radiation from the visible spectrum to drive the synthesis of sugar molecules. Special pigments in chloroplasts of plant cells absorb the energy of certain wavelengths of light, causing a molecular chain reaction known as the light-dependent reactions of photosynthesis.

The best wavelengths of visible light for photosynthesis fall within the blue range (425–450 nm) and red range (600–700 nm). Therefore, the best light sources for photosynthesis should ideally emit light in the blue and red ranges. In this study, we used a with a and to collect spectra from four different light sources.

This allowed us to determine the wavelengths emitted by each source and to get an idea of their relative intensities. Wavelengths of light outside of the red and blue ranges are not used by most plants, and can contribute to heat build-up in plant tissues.

1. This heat can damage plants and even interfere with photosynthesis.
2. In order to identify the ideal light source for photosynthesis studies we compared the output or emission spectra of four different E27 type bulbs in the same desk lamp: a) 60 W incandescent bulb, b) 35 W halogen bulb, c) 28 W-equivalent LED “plant bulb” (6–9 W), and d) 13 W compact fluorescent light (CFL) bulb.

Each light was measured at a standard distance of 50 cm. Relative light intensity of four light bulbs across the visible spectrum Based on our results, the best light bulb for promoting photosynthesis in plants was the LED plant bulb. This bulb produces a strong output in both the blue and red wavelengths, with very little additional light in other regions to cause heat build-up.

1. All of the other light sources had very little output in the blue range.
2. The halogen and incandescent bulbs had extremely broad output ranges from green to deep into the red portion of the spectrum, but with little to nothing in the blue range.
3. The least suitable lamp for photosynthesis was the CFL bulb.

While it emitted some light in both the blue and red ranges (with several peaks in between), the intensity of this bulb was the weakest when compared to all the other lamps. LED plant lights are available from a variety of online merchants and home and garden stores.

How do plants respond to high light intensity?

Plants response to light stress , August 2022, Pages 735-747 The chloroplasts of plants convert carbon dioxide and water into organic matter and oxygen using solar energy. Light not only provides energy for photosynthesis, but it is also an important environmental factor since light intensity and spectral quality exhibit temporal and spatial variation.

When light conditions are not suitable for plant growth, light can become a major abiotic stress factor (Fiorucci and Fankhauser, 2017). Low light intensity does not provide enough energy for plant growth, but high light intensity can cause photodamage to plants while fluctuating light intensity can also reduce photosynthetic efficiency.

When plants are exposed to light stress (especially high light stress), photoinhibition is activated, resulting in an imbalanced energy distribution between Photosystem I (PSI) and Photosystem II (PSII) and a rapid decline in photosynthetic efficiency (Walters, 2005).

To respond to light stress, plants have evolved a variety of self-protection mechanisms, such as producing and scavenging chloroplastic ROS, moving chloroplasts and opening or closing stomata, producing anthocyanins, and coordinating responses via systemic signaling. Photosynthetic apparatuses, the molecular machines actually performing photosynthesis, are easily damaged by light stress and therefore have evolved strategies to rapidly respond to light stress by, for instance, modulating the complex structures and states of thylakoid membrane-bound proteins (Pottosin and Shabala, 2016).

This review summarizes recent findings regarding various photoprotection mechanisms of plants adapting to light stress, with a focus on the response mechanisms of photosynthetic apparatuses to high light and fluctuating light intensities. Absorption of excess light can lead to increased production of excited, highly reactive photosynthesis intermediates, which expose plants to serious risks of photodamage (Bassi and Dall’Osto, 2021).

Prevention and replication of light stress are performed by photoprotective molecules and mechanisms, which are composed of various components, including phytohormones, transcription factors, mitogen-activated protein kinases, and operated by limiting the generation of redox-active molecules, Light stress leads to overproduce chloroplastic ROS that are implicated in both signaling and oxidative damage.

Initially regarded as harmful substances from aerobic metabolism, ROS are considered to be major regulatory molecules in plants and function in early signaling transduction induced by light stress (Exposito-Rodriguez et al., 2017). The production of chloroplastic ROS is regulated by the harvesting and the distribution of light energy to photosynthetic apparatuses.

The major sources of Chloroplast photo-relocation movement is an important phenomenon that protects plants from high light-intensity stress, as well as enhances the photosynthesis of plants under low light conditions. Chloroplast movement is also pivotal for plants living under fluctuating light conditions (e.g., under canopies) (Wada and Kong, 2011).

Chloroplasts accumulate in areas irradiated with weak light to capture light efficiently (the accumulation response or low-light response) and escape to anticlinal Stomatal movements regulate gas exchange between plants and the atmosphere and minimize transpirational water loss, optimizing the overall adjustment of plants to abrupt changes in light conditions.

• Rapid changes in the size of stomatal aperture manage the availability of CO 2 for photosynthesis and match this availability to corresponding light intensity, individual leaf temperature, and overall plant transpiration (Merilo et al., 2015).
• Stomatal opening driven by the accumulation of K + and Natural light environments are highly variable because light intensities could change drastically due to the leaf angle, cloud cover, or changes in sun elevation.

What is more, plants are subjected to severe competition for light because of surrounding neighbors. Therefore, plants develop numerous adaptations to increase their competitiveness and fitness in the field. Long-term acclimation to fluctuating light is triggered inside leaves within hours to days, such as a set of growth and Plants have developed several mechanisms to deal with high light stress during the long evolutionary process.

• The accumulation of nonphotosynthetic pigments, especially anthocyanins in photosynthesis tissues, is an important mechanism for plants to regulate light energy absorption (Albert et al., 2009).
• Anthocyanins are one kind of water-soluble pigments that are widely present and belong to the flavonoids.
• Anthocyanins are mainly present in the vacuoles of plant epidermal cells in the form of In plants, a plethora of chemical and physical signals are transmitted from a single leaf (a local tissue) subjected to stress to the entire plant (systemic tissues).

These signals, collectively termed systemic signals, include different chemicals, such as ROS waves, phytohormones, and other low molecular weight compounds, as well as physical signals (Suzuki et al., 2013; Devireddy et al., 2018). Previous studies have shown that sulfur metabolism and oxylipin signaling participate in the high When plants encounter high light stress, PSII is readily inactivated, and photosynthetic efficiency decreases rapidly, which is called photoinhibition (Roach and Krieger-Liszkay, 2014).

To dissipate the high light energy absorbed by PSII, plants can eliminate it through photochemical and nonphotochemical quenching processes (Szymanska et al., 2017). In addition, the light-inducible response is associated with the phenomenon of state transitions (Haldrup et al., 2001). Plants regulate their Plants dissipate excess light energy in the form of heat through light-harvesting complexes of the photosystem to prevent ROS damage, which is one of the most important fast photoprotective mechanisms (Foyer, 2018).

The exposure of plants to high-intensity light that exceeds the energetic demand of the plants or their capacity to dissipate the excessive light energy may cause a range of high light stress responses (Ruban, 2016). NPQ dissipates excess excitation energy as heat and is broadly Photosynthesis requires the coordinated function of several large membrane complexes: PSII, the Cytochrome b 6 f complex (Cyt b 6 f ), PSI, and ATP synthase (ATPase).

PSII is an integral-membrane multisubunit pigment-protein complex that splits water into oxygen, protons, and electrons during the photosynthetic process (Nickelsen and Rengstl, 2013). The de novo assembly and reassembly cycle of PSII is a highly conserved process from cyanobacteria to vascular plants.

The de novo assembly process of Photosynthetic apparatuses are inevitably exposed to serious risks of oxidative damage when the absorption of light energy exceeds the carrying capacity of the photosynthetic electron transfer chain under high light stress (Takahashi and Badger, 2011).

PSII-LHCII supercomplexes are especially susceptible to damage under high light conditions, and the mechanisms of PSII photoinhibition have been studied extensively (Gururani et al., 2015). Previous research has shown that the damage to PSII When PSII is damaged by high light stress, a series of effective repair mechanisms are activated.

The most central mechanism of the PSII repair cycle is the decomposition, degradation, and resynthesis of subunit component D1 protein in PSII, which can alleviate the damage to the PSII reaction center to maintain the productivity of photosynthesis (Nixon et al., 2010).

The photorepair process is facilitated by the phosphorylation of the PSII core and LHCII under high light stress. The Plant chloroplasts evolved from cyanobacteria through endosymbiosis. The mature chloroplast typically encodes 75–80 proteins among the estimated 3500–4000 proteins present in the chloroplast, indicating that chloroplasts integrated most genes into the plant genome during evolution and retained only a few key genes for chloroplast development and photosynthesis.

As shown in Fig.2, the nuclear genes encoding chloroplast proteins are usually activated by light-induced transcription factors, then As sessile organisms, plants experience a range of light intensities in the natural environment due to the leaf angle, cloud cover, shading from neighboring plants, or changes in sun elevation.

• Therefore, plants develop several strategies to cope with fluctuating light to maintain high photosynthetic efficiency and avoid damage to the photosynthetic apparatus (Morales and Kaiser, 2020; Gjindali et al., 2021).
• The mechanisms of fluctuating light acclimation include state transitions, cyclic Photosynthetic organisms are constantly subjected to a fluctuating environment in which light intensity and quality change continuously.

Thus, an imbalance in the flow of electrons between PSI and PSII would appear due to unequal excitation of two photosystems while aborting light. This imbalance could trigger the formation of dangerous ROS, which may damage biomolecules once excessive accumulation occurs (Foyer and Noctor, 2009).

• State transitions are strategies to deal with this imbalance, To deal with dynamic fluctuations in light intensity and variable demand for ATP and NADPH, plants must rapidly regulate photosynthetic electron transport in the thylakoid membrane of chloroplasts.
• The light energy collected by chlorophylls during photosynthesis drives the electron transport process via PSI and PSII (Das et al., 2021).

Photosynthesis contains two distinct electron transport pathways: linear electron transport (LET) and cyclic electron transport (CET). In LET, electrons are Several thylakoid regulatory proteins have been reported to function in fluctuating light adaptation processes, independent of state transitions or cyclic electron transport (Fig.3B).

• For example, PSB27, a thylakoid lumen protein, plays an essential role in enabling plants to adapt to fluctuating light intensity (Hou et al., 2015).
• Another thylakoid lumen protein, PSB33, sustains D1 protein under fluctuating light conditions (Fristedt et al., 2017).
• TLP18.3, an acidic phosphatase, participates Plants in the natural environment have to respond to a variety of stresses, including light stress.

Light stress detrimentally affects photosynthetic efficiency and can vary in intensity and duration, lasting anywhere from seconds to months. Therefore, effective protection strategies are essential for plant growth, survival, and reproduction. Plants are indeed equipped with a variety of protection mechanisms, including regulating the generation of redox-active molecules, scavenging ROS, The authors declare that no conflict of interest exists.

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Chloroplasts are unique organelles that not only provide sites for photosynthesis and many metabolic processes, but also are sensitive to various environmental stresses. Chloroplast proteins are encoded by genes from both nuclear and chloroplast genomes. During chloroplast development and responses to stresses, the robust protein quality control systems are essential for regulation of protein homeostasis and the integrity of chloroplast proteome. In this review, we summarize the regulatory mechanisms of chloroplast protein degradation refer to protease system, ubiquitin-proteasome system, and the chloroplast autophagy. These mechanisms symbiotically play a vital role in chloroplast development and photosynthesis under both normal or stress conditions. Light is essential for plants, but excessive light is damaging to plant health. Photoprotection is defined as the prevention against damaging effects of intense solar radiation. Plants have evolved morpho-physiological and biochemical adaptations to shield themselves from harmful radiations. Secondary metabolites are low molecular weight organic compounds that play manifold roles in plants including defense and interactions with the environment. Flavonoids are phenolic compounds while carotenoids are tetraterpenes that play crucial role in photoprotection. Several studies indicate that light regulates the accumulation of these metabolites. The underlying mechanistic details about the light signaling factors regulating the synthesis of these secondary metabolites have expanded over the last few years. These include the photoreceptors PHY, CRY and UVR8, light-regulated transcription factors like HY5, PIFs, MYBs and BBXs and their downstream targets PSY, CHI, CHS, FLS, that modulate carotenoid and flavonoid biosynthesis. Here we discuss these molecular mechanisms and how metabolic engineering is now being used to modulate these pathways, to enhance the production of beneficial metabolites. This can be useful for the generation of climate-resilient plants resistant to excessive radiation in the future. Additionally, optimum artificial lighting can enhance the production of these metabolites which often have nutritional and medicinal benefits. The β-carotene hydroxylase gene ( BCH ) regulates zeaxanthin production in response to high light levels ro protect Chrysanthemum morifolium plants against light-induced damage. In this study, the Chrysanthemum morifolium CmBCH1 and CmBCH2 genes were cloned and their functional importance was assessed by overexpressing them in Arabidopsis thaliana, These transgenic plants were evaluated for gene-related changes in phenotypic characteristics, photosynthetic activity, fluorescence properties, carotenoid biosynthesis, aboveground/belowground biomass, pigment content, and the expression of light-regulated genes under conditions of high light stress relative to wild-type (WT) plants. When exposed to high light stress, WT A. thaliana leaves turned yellow and the overall biomass was reduced compared to that of the transgenic plants. WT plants exposed to high light stress also exhibited significant reductions in the net photosynthetic rate, stomatal conductance, Fv/Fm, qP, and ETR, whereas these changes were not observed in the transgenic CmBCH1 and CmBCH2 plants. Lutein and zaxanthin levels were significantly increased in the transgenic CmBCH1 and CmBCH2 lines, with progressive induction with prolonged light exposure, whereas no significant changes were observed in light-exposed WT plants. The transgenic plants also expressed higher levels of most carotenoid biosynthesis pathway genes, including phytoene synthase ( AtPSY ), phytoene desaturase ( AtPDS ), lycopene-β-cyclase ( AtLYCB ), and ζ-carotene desaturase ( AtZDS ). The elongated hypocotyl 5 ( HY5 ) and succinate dehydrogenase ( SDH ) genes were significantly induced following exposure to high light conditions for 12h, whereas phytochrome-interacting factor 7 ( PIF7 ) was significantly downregulated in these plants. Growing concerns over greenhouse gas emissions and energy insecurity caused by the depletion of conventional fuels have led to a search for sustainable fuel alternatives. As an alternative energy carrier, hydrogen (H 2 ) is particularly attractive as only water is released during combustion. The process of H 2 production from genetically engineered phototrophic microorganisms through biophotolysis leads the way to solve energy shortages. Genetically engineered cyanobacteria species are potential candidates due to their superior properties for reducing greenhouse gases and using solar energy as an energy source. The review discusses the mechanisms and enzymes involved in H 2 production by cyanobacteria and applications of genetic engineering. A critical analysis of the fundamental issues attributed to the technical advancement of photobiological cyanobacteria-based H 2 production is provided, as well as the perspectives for future research to reduce carbon dioxide emissions through the creation of waste-free technology.

Plant diseases caused by diverse pathogens lead to a serious reduction in crop yield and threaten food security worldwide. Genetic improvement of plant immunity is considered as the most effective and sustainable approach to control crop diseases. In the last decade, our understanding of plant immunity at both molecular and genomic levels has improved greatly. Combined with advances in biotechnologies, particularly clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9-based genome editing, we can now rapidly identify new resistance genes and engineer disease-resistance crop plants like never before. In this review, we summarize the current knowledge of plant immunity and outline existing and new strategies for disease resistance improvement in crop plants. We also discuss existing challenges in this field and suggest directions for future studies. Plasma membrane H + -ATPases (PM H + -ATPases) are critical proton pumps that export protons from the cytoplasm to the apoplast. The resulting proton gradient and difference in electrical potential energize various secondary active transport events. PM H + -ATPases play essential roles in plant growth, development, and stress responses. In this review, we focus on recent studies of the mechanism of PM H + -ATPases in response to abiotic stresses in plants, such as salt and high pH, temperature, drought, light, macronutrient deficiency, acidic soil and aluminum stress, as well as heavy metal toxicity. Moreover, we discuss remaining outstanding questions about how PM H + -ATPases contribute to abiotic stress responses. Hydrogen sulfide (H 2 S) was once principally considered the perpetrator of plant growth cessation and cell death. However, this has become an antiquated view, with cumulative evidence showing that the H 2 S serves as a biological signaling molecule notably involved in abiotic stress response and adaptation, such as defense by phytohormone activation, stomatal movement, gene reprogramming, and plant growth modulation. Reactive oxygen species (ROS)-dependent oxidative stress is involved in these responses. Remarkably, an ever-growing body of evidence indicates that H 2 S can directly interact with ROS processing systems in a redox-dependent manner, while it has been gradually recognized that H 2 S-based posttranslational modifications of key protein cysteine residues determine stress responses. Furthermore, the reciprocal interplay between H 2 S and nitric oxide (NO) in regulating oxidative stress has significant importance. The interaction of H 2 S with NO and ROS during acclimation to abiotic stress may vary from synergism to antagonism. However, the molecular pathways and factors involved remain to be identified. This review not only aims to provide updated information on H 2 S action in regulating ROS-dependent redox homeostasis and signaling, but also discusses the mechanisms of H 2 S-dependent regulation in the context of oxidative stress elicited by environmental cues. In recent years, it has been established that microRNAs (miRNAs) are critical for various plant physiological regulations in numerous species. Next-generation sequencing technologies have aided to our understandings related to the critical role of miRNAs during environmental stress conditions and plant development. Light influences not just miRNA accumulation but also their biological activities via regulating miRNA gene transcription, biosynthesis, and RNA-induced silencing complex (RISC) activity. Light-regulated routes, processes, and activities can all be affected by miRNAs. Here, we will explore how light affects miRNA gene expression and how conserved and novel miRNAs exhibit altered expression across different plant species in response to variable light quality. Here, we will mainly discuss recent advances in understanding how miRNAs are involved in photomorphogenesis, and photoperiod-dependent plant biological processes such as cell proliferation, metabolism, chlorophyll pigment synthesis and axillary bud growth. The review concludes by presenting future prospects via hoping that light-responsive miRNAs can be exploited in a better way to engineer economically important crops to ensure future food security. Photoinhibition is one of the most controversial topics in photophysiology. Well into the 21 st century, scientists have not agreed on the mechanism of action, primary site, and roles of excess energy absorbed by photosynthetic pigments. It is recognized that Photosystem II is the most fragile component during photoinhibition and that excess excitation absorbed by the photosynthetic pigments has a strong impact on it. Consensus is yet to come on terminology, guidelines to study photoinhibition, or boundaries of what can be considered photodamage. Some of these controversies are the result of how we understand the phenomenon of photoinhibition, as this is what determines a given experimental design. Thus, how we understand photodamage depends on the philosophical approach of each group. While some efforts have been made in the parametrization of Photosystem II photoinhibition, an updated review about the concepts of photoinhibition of Photosystem II and how to study it is still pending. In this work, a review of the concepts used in the field of photoinhibition is presented, accompanied by a synopsis on the history and mechanisms of action. Irradiation with artificial lighting in greenhouses and plant factories is mainly used to promote photosynthesis in tomato cultivation. In addition to photosynthesis, the light effects on morphology, flowering, and metabolism are also crucial as plant responses. Light period and quality have been studied for a long time in relation to the flowering of cut-flowers, strawberries, and many leafy vegetables. Light quality, such as red, far-red, and blue, should be considered with their photoreceptors containing phytochrome, cryptochrome, and flavin-binding kelch repeat, F-box 1. Light quality may also affect plant morphogenesis and the accumulation of valuable metabolites, and plant growth regulators (PGRs) are understandably related to them. However, the effects of PGRs, light quality, and photoreceptors on morphogenesis and metabolite accumulation have been only reported individually and have not been comprehensively discussed. In this review, the information on tomatoes, which are important both industrially and academically, was mainly summarized and discussed. Effects of light quality on plant growth, fruit ripening and metabolite accumulation, and biotic and abiotic stresses, as well as the involvement of gibberellin, auxin, ethylene, abscisic acid, jasmonic acid, and salicylic acid, are discussed here with the roles of the photoreceptors of each light quality and light signal integrators. There is no safety problem for light quality use with appropriate wavelength and intensity, and it is environmentally friendly to use light-emitting diodes as an energy-saving light source. Therefore, once their effect is clear with scientific evidence in relation to PGRs, light quality control technology can be used and contribute to the improvement of production and quality of tomatoes with the usage of PGRs.

: Plants response to light stress

Why does blue light slow photosynthesis?

Blue photons drive the photosynthetic reaction, although from an energy standpoint, one might consider them less efficient than green or red photons because their high energy isn’t fully utilized ; some of the energy is essentially lost compared to photosynthetic photons with a longer (less energetic) wavelength.

Why does red light slow down photosynthesis?

3. Discussion – The structure and physiology of plants are particularly regulated by light signals from the environment, as the primary response of plants during photosynthesis completely depends on light conditions. Plant growth and productivity depends on the light conditions and photosynthetic metabolism is detrimentally affected by light intensity.

Plants have developed a sophisticated mechanism to adapt their structure and physiology to the light environment. In this study, we demonstrate that blue LEDs with high light intensity superimpose over red and green LEDs. Plants grown under blue LEDs successfully induced maximum Ψ W (water potential) to −2.33 MPa and fell to a minimum value of −0.233 MPa in leaves of plants grown at green LEDs ( Figure 1E ).

Exposure to green LEDs reduces biomass at low light intensity and a biomass increase was observed under blue LEDs at 238 μmol m −1 s −1, These results give a clear indication that blue LEDs in combination with high light intensities are more efficient for biomass production in plants.

1. Red and blue light is important for expansion of the leaf and enhancement of biomass,
2. Yorio et al,
3. Reported that there was higher weight accumulation in lettuce grown under red light supplemented with blue light than in lettuce grown under red light alone.
4. However, the shoot dry matter weight of leaf lettuce plants irradiated with blue light decreased compared with that of white light,

In the present experiments, blue LEDs in combination with high light intensity was important for growth elongation and biomass accumulation compared to plants grown under low light intensities. Physiological studies of photosynthesis conducted for many years have considered various light conditions.

1. A combination of red and blue LEDs is an effective source for photosynthesis using different light intensities and wave lengths.
2. Blue LEDs deficiency can result in acclimations of light energy partitioning in PSII and CO 2 to high irradiance in spinach leaves,
3. Presently, lettuce plants depended on high light intensity ( Figure 2 ) and LEDs for higher rate of photosynthesis.

The higher rate of photosynthesis at 238 μmol m −1 s −1 in plants grown at blue LEDs indicated that lettuce plants displayed pronounced acclimation of photosystems for CO 2 fixation than plants grown under red and green LEDs. A lower photosynthetic rate in plants grown under red LEDs has been observed in several crops including rice and in wheat,

1. The reduced rate of photosynthesis under low light intensity and red LEDs suggests that vulnerability to a decreased the photosynthetic rate might be associated with changes in multiprotein complexes (PSI and PSII).
2. The lower rate of photosynthesis in red LEDs can also be attributed to low nitrogen content in leaves, due to low chlorophyll and carotenoid content, which was also observed in the present study (data not shown),

The stomata are important channels for the exchange of water and gases with external environmental conditions. Light influences stomata conductivity and proton motive forces, The development of stomata has been related to light intensity, Our results agree with these previous findings and additionally show that blue LEDs are more efficient in stomatal structure and opening and closing of stomata ( Figure 3 ).

1. The number of stomata increased more in plants grown under blue LEDs at 238 μmol m −1 s −1 compared to plants grown under low light intensities and other LEDs.
2. The closure and reduced number of stomata might be due to defoliation of leaves under low light intensity during growth of lettuce.
3. Indeed, high temperatures under different light intensity conditions might induce palisade and increased sponge parenchyma cell length and thickness,

The closure of stomata with reduced normalized expression and number might be also the reason for reduction of transpiration rate and stomatal conductance in lettuce which were grown under green LEDs more so than those grown under blue LEDs. The thylakoid membranes are the sub-compartments in which the primary reactions of photosynthesis occur.

About 100 proteins are involved in these reactions; they are organized in four major multisubunit protein complexes: PSI, PSII, ATP synthase complex and cytochrome b6/f (cyt b6/f) complex, Proteomics of the thylakoid membrane are an excellent approach to establish the number and identity of the proteins localized to this sub-compartment in pigment–multiprotein complexes, and to study the impact of light intensity and light source on them for increased photosynthetic metabolism and other physiological process.

Several diverse photosynthetic factors have been observed at different light intensities with inhibition of photosynthetic factors associated with carbohydrate metabolism in leaves, However, to date there is no information on the expression of thylakoid proteins under different intensities of light and light sources.

Our results show that the induction in the expression of PSII-core dimer under blue LEDs at 238 μmol m −1 s −1 ( Figure 4A ). The reduction of these multiprotein complexes at red and green LEDs might limit mineral nutrient clusters which are associated with the chloroplast membrane, In addition to this, leaves exposed to green LEDs might reject light due to chlorosis that occurs due to proteolytic loss of photosystems and the cytb 6 /f complex and the light-harvesting chlorophylls and carotenoids.

The inhibition of PSI and PSII under red and green LEDs with low light intensity suggests the involvement of an unidentified problem related to transport of substances in plants are due to reduced amounts of core antenna Chl-protein complexes, The involvement of blue LEDs at high light intensity leads to maintenance of PSI and PSII core complexes.

In some reports, it has been postulated that the intensity of blue light for activation of PSII core protein content in Arabidopsis acting via cryptochromes, along with non-blue specific activation signals Our data clearly show that RuBisCO was expressed at 238 μmol m −1 s −1 whereas it was absent in plants grown under green LED light sources ( Figure 4B,C ) which were positively paralleled with other multiprotein complexes.

The enhancement of RuBisCO under high intensity of blue LED might be associated with an increase in the amount of N content accompanied by induction of chlorophyll content or it might be also due to wider and thinner expansion of palisade and sponge parenchyma.

1. The induction of RuBisCO in plants grown under blue LED light might be also due the expansion of palisade and sponge parenchyma.
2. Reduction of thylakoid protein complexes and photosynthetic parameters under green and red LEDs at low light intensity indicate a close dependence of the photosynthetic metabolism on the source of light and its intensity.

The proteins of chloroplast sub-compartments under blue LEDs at high light intensity optimize photosynthesis and provide an advantage for higher growth and development of plants than those grown under red and green LEDs at low light intensities.

How does light affect photosynthesis?

At low light intensities, above the light compensation point (LCP), photosynthetic rate increases proportionally to the light intensity and reaches a maximum. However, as light intensity is increased further, chlorophyll can get damaged and as a result the rate of photosynthesis decreases.

Do plants photosynthesize with low light?

Introduction – Light is one of the most important environmental factors and plays a critical function in plant development and metabolism, Additionally, light is indispensable for photosynthesis and photomorphogenesis. Low light is a pervasive abiotic stress in plant breeding and cultivation due to light block from horticulture facilities, clouds and snow.

Low light was shown to substantially affect the agronomic traits of plants and inhibit physiological metabolic processes, including photosynthesis and antioxidant characteristics, as well as carbon and nitrogen fixation, It causes slow growth, decrease of leaf weight and flower bud number. Furthermore, this stressor reduces sugar and starch contents in eggplant, grape and rice, and changes the coloration and extends the maturity time in cherry,

Chlorophyll is an important pigment involved in absorbing, transmitting and converting solar energy into electrochemical energy, It was reported that low light-tolerant hybrid rice -exhibited a higher content of chlorophyll b following exposure to low light.

Low light negatively affects stomata conductance and results in enhanced concentration of intercellular CO 2 in rice leaves, Moreover, stomata conductance and photosynthetic efficiency under low light decreases by the number of 24.31% and 79.84%, respectively compared to that of natural light, Antioxidant metabolism plays an important role in protecting plants from a wide variety of environmental stresses, such as drought, extreme temperatures, pollutants, ultraviolet radiation and high levels of light,

Enhancement of antioxidant defense in plants can thus increase tolerance to different stresses. Antioxidants include the enzymes peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and superoxide dismutase (SOD), Analyses of membrane lipid peroxidation in peach fruit showed that decreasing the light intensity decreased CAT, G-POD and APX activity but increased malondialdehyde (MDA) content with more cell membrane damage,

Pak-choi ( Brassica campestris ssp. Chinensis Makino L.) originated from China is one of the most important vegetables worldwide in terms of its planting areas and annual yields. Purple pak-choi contains high levels of light-dependent anthocyanin in its leaves. This plant is very popular in China, Japan and surrounding countries.

Anthocyanins, a class of secondary metabolites, contribute to the red, blue, and purple colors in flowers, fruits, and leaves, They also act as antioxidants and protect DNA and the photosynthetic apparatus from damage due to high radiation fluxes, Additionally anthocyanin protects plants against cold and drought stress,

• Anthocyanin is accumulated in response to light in the seedlings of mustard and tomato.
• Phytochrome is an important photoreceptor controlling the accumulation of anthocyanins,
• However, how phytochrome regulates anthocyanin and other key enzymes under low light remains unclear.
• Anthocyanin is synthesized via a branch of the phenylpropanoid pathway, i.e., the flavonoid pathway ( Fig 1 ),

Anthocyanin biosynthesis consists of sequential reactions leading to the production of different anthocyanins. The gene structure of 73 anthocyanin biosynthetic genes was identified in B, rapa, These gene expression analyses showed that almost all late biosynthetic genes of anthocyanin were highly up-regulated in all purple leaves of Brassica, Diagram of the flavonoid pathway. The enzymes for each step are italicized, with the following enzymes required for anthocyanin biosynthesis: chalcone synthase ( CHS ), chalcone isomerase ( CHI ), flavanone-3-hydroxylase ( F3H ), dihydroflavonol-4-reductase ( DFR ), anthocyanidin synthase ( ANS ), anthocyanidin reductase ( ANR ) and UDP-glucose: flavonoid-3-O-glycosyltranferase ( UFGT ).

Cominelli et al. investigated different light treatments and found that the activities of ANS and ANR in Arabidopsis were related to their gene expression level. The regulation of anthocyanin accumulation under different light levels was shown to be due to transcriptional control or transcription factors,

The lowest light levels caused death and decreased anthocyanin content in Anacampseros rufescens, maize and perilla, The shading of stems and leaves of Eustoma grandiflorum resulted in a significant anthocyanin reduction in petal color, while incubation in complete darkness was beneficial to the nutritional quality of the brassica sprouts,

When B, rapa was exposed to low light, the levels of phenolics and shoot biomass were reduced, Still, a comprehensive study of physiological change after low light treatment is lacking. Thus, we investigated the responses of various plant parameters, such as photosynthesis, chlorophyll, and the activities of anthocyanin biosynthetic and antioxidant enzymes, in purple pak-choi under low light stress by shading the plants in a phytotron.

Moreover, the examination of anthocyanin accumulation in this purple plant under different low light intensities provides invaluable guidance for artificially supplementing light intensity in agricultural facilities.

Can photosynthesis occur in low light?

Conclusion and Future Perspective – The PPFD of O 2 -evolving photolithotrophs on earth appears to be able to generate photosynthesis at 10 nmol photons m –2 s –1, Vascular plants have a similar photosynthetic process and equivalent energy demand. The numerous antenna pigments harvest photons and focus on one RC, and consequently generate the electronic potential for charge separation in vascular plant leaves.

• The fast and effective electron transfer prevents quenching and returning of the electron, which remains steady electron flux in the photosynthetic membrane.
• The electron can be accumulated for water-splitting through state S 0 to S 4, resulting in O 2 evolving.
• Stomata, which may be different from photolithotrophs, cannot restraint gas exchange in the dim light, even if in darkness.

The biochemical reaction Calvin cycle is also proved to be partially active in dim light. From the above, both reactions (dark reaction and light reaction) of photosynthesis can be conducted in dim light. Dim light occurs widely and lasts for a long time in natural and artificial environments, and this article showed that the photosynthesis of plant leaves could occur in this light condition.

1. Thus, the increasing scenes of dim light might cause more contributions from the vascular plant to atmospheric carbon dioxide concentration on local or regional scales, which was closely related to plant development, crop yield, and climate change.
2. In the future, the impact of dim light on plant photosynthesis should be investigated like normal light, and the models for estimation of crop yield and carbon budget should take dim light into consideration.

The successful investigation to comprehend the utilization of dim light will require technological advancements to measure light characteristics and detecting methods to measure gas exchange at ecologically relevant levels in various field conditions, with theoretical foundations from this review.

Why does light intensity affect the rate of transpiration?

External Factors Affecting Transpiration – There are several external factors which can affect transpiration, as mentioned in the sections above, such as:

Light intensity – higher light intensity levels will generally result in greater transpiration rates. This is because plants open their stomata in response to light, allowing water vapour to escape from the leaves. However, there are some exceptions to this rule.

For example, if the air around the leaves is arid, the plant may close its stomata to prevent further water loss, This can happen even if the light intensity is high, Similarly, if the temperature is very high, the plant may close its stomata to reduce water loss, even if the light intensity is low,

• Temperature – as temperature increases, so does the rate of transpiration. The lower the temperatures, the lower the transpiration rate. Guard cells tend to close the stomata in windy conditions to prevent that.
• Wind – generates more water loss because they lead to higher evaporation rates. Guard cells tend to close the stomata in windy conditions to prevent that.
• Humidity – low humidity means the plant needs to retain more water and typically develops leaves with a lesser surface area, thicker cuticles, etc.

In plant physiology, transpiration pull is the force created by water loss through transpiration which pulls water upwards through a plant. This force is created by the evaporation of water from the leaves, which creates a pressure gradient from the leaves to the roots.

How does light intensity affect the rate of oxygen production in photosynthesis?

Oxygen production increased as the light intensity increased due the greater availability of light energy for photosynthesis.

How does sunlight affect photosynthesis?

Image Credit: USDA Forest Service Southern Research Station, USDA Forest Service, SRS, Bugwood.org, CC BY 3.0 US – ” image=”image1″> Plants use a process called photosynthesis to make food. During photosynthesis, plants trap light energy with their leaves. Plants use the energy of the sun to change water and carbon dioxide into a sugar called glucose, Glucose is used by plants for energy and to make other substances like cellulose and starch, Cellulose is used in building cell walls. Starch is stored in seeds and other plant parts as a food source. That’s why some foods that we eat, like rice and grains, are packed with starch!

How does light wavelength affect photosynthesis?

Passing white light through a prism separates the light into different wavelengths, appearing as a rainbow of colors. The order of colors is determined by the wavelength of light. For visible light, red has the longest wavelength and violet has the shortest wavelength. However, visible light is just a small portion of the electromagnetic spectrum. Energy is inversely porportional to the wavelength – longer wavelengths have less energy than shorter wavelengths. For example, UV light has a shorter wavelength and more energy than visible light. A pigment is any substance that absorbs light. The color of the pigment comes from the wavelengths of light that are reflected, or in other words, those wavelengths not absorbed. Chlorophyll, the green pigment common to all photosynthetic cells, absorbs all wavelengths of visible light except green, which it reflects. Each pigment has a characteristic absorption spectrum describing how it absorbs or reflects different wavelengths of light. Wavelengths absorbed by chlorophyll and other photosynthetic pigments generate electrons to power photosynthesis. All photosynthetic organisms have chlorophyll a which absorbs violet-blue and reddish orange-red wavelengths. Chlorophyll a reflects green and yellow-green wavelengths. Accessory photosynthetic pigments, including chlorophyll b and beta-carotene, absorb energy that chlorophyll a does not absorb. Chlorophyll only triggers a chemical reaction when it is associated with proteins embedded in a membrane, such as in thylakoid membranes of the chloroplast or membrane infoldings found in photosynthetic prokaryotes.