Effects of Different Spectra from LED on the Growth,Development and Reproduction of <i>Arabidopsis thaliana</i>

Light is the major source of energy for plants and as such has a profound effect on plant growth and development. Red and blue lights have been considered to best drive photosynthetic metabolism and are beneficial for plant growth and development, and green light was seen as a signal to slow down or stop. In this study, Arabidopsis thaliana (Arabidopsis) was used to investigate the effects of red, blue and green lights on the growth and development of plants from seed germination to seeding. Results demonstrated that red light showed a promotion effect but blue light a prohibition one in most stages except for the flowering time in which the effect of each light was just reversed. When mixed with red or blue light, green light generally at least partially cancelled out the effects caused by each of them. Results also showed that the same number of photons the plant received could cause different effects and choosing the right combination of different color of lights is essential in both promoting the growth and development of plants and reducing the energy consumption of lighting in plant factory.     

光质对白芨组培苗生理特性及酶基因表达的影响

为探讨光质对白芨(Bletilla striata)组培苗生长发育的影响,对不同光质下白芨组培苗的生长特征、抗氧化酶活性以及酶基因表达进行了研究。结果表明,蓝光和红光对白芨生长有显著促进作用,绿光的作用不明显。除了CAT外,不同光质处理白芨的APX、POD、SOD活性均呈上升趋势,且黄光处理的白芨SOD和APX活性最高,红光处理的POD活性最高,绿光处理的抗氧化酶活性比其他光质的低,蓝光处理35~45 d对抗氧化酶基因表达具有促进作用。因此,红光和黄光促进白芨生根组培苗的长高和生根;不同光质处理总体上提高了白芨氧化酶活性;白芨抗氧化酶基因的表达在蓝光处理下最大。     

Green light signaling and adaptive response

To a plant, the sun’s light is not exclusively energy for photosynthesis, it also provides a package of data about time and prevailing conditions. The plant’s surroundings may dampen or filter solar energies, altering spectral profiles of their light environment. Plants use this information to adjust form and physiology, tailoring gene expression to best match ambient conditions. Extensive literature exists on how blue, red and far-red light contribute to plant adaptive responses. A growing body of work identifies discrete effects of green light (500–565 nm) that also shape plant biology. Green light responses are known to be either mediated through, or independent of, the cryptochrome blue light receptors. Responses to green light share a general tendency to oppose blue- or red-light-induced responses, including stem growth rate inhibition, anthocyanin accumulation or chloroplast gene expression. Recent evidence demonstrates a role for green light in sensing a shaded environment, independent from far-red shade responses.     

光质对植物光合作用的调控及其机理

光合作用是植物生长发育的基础.光质对植物光合作用的调控主要包括可见光对植物气孔器运动、叶片生长、叶绿体结构、光合色素、D1蛋白及其编码基因和光合碳同化等的调节,以及紫外光对植物光系统Ⅱ的影响.蓝光和红光能促进气孔的开张,而绿光能够逆转这种作用.蓝光有利于叶绿体的发育,红、蓝、绿复合光有利于叶面积的扩展,而红光更有利于光合产物的积累;不同光质对不同植物、不同组织器官叶绿素积累的影响不同.蓝光和远红光可以促进psbA基因转录物质的积累.大多数高等植物和绿藻在橙、红光下光合速率最高,蓝紫光其次,绿光最低.紫外光可以导致光系统Ⅱ的电子传递活性下降.此外,针对光质与光合作用研究领域中存在的问题,对今后的研究方向进行了讨论.     

Analyzing photosynthetic activity and growth of Solanum lycopersicum seedlings exposed to different light qualities

To investigate how light quality influences tomato (Solanum lycopersicum L) seedlings, we examined changes in plant growth, chloroplast ultrastructure, photosynthetic parameters and some photosynthesis-related genes expression levels. For this, tomato plants were grown under different light qualities with the same photosynthetic photon flux density: red (R), blue (B), yellow (Y), green (G) and white (W) lights. Our results revealed that, compared with plants grown under W light, the growth of plants grown under monochromatic lights was inhibited with the growth reduction being more significant in the plants grown under Y and G lights. However, the monochromatic lights had their own effects on the growth and photosynthetic function of tomato seedlings. The plant height was reduced under blue light, but expression of rbcS, rbcL, psbA, psbB genes was up-regulated, and the ΦPSII and electron transport rate (ETR) values were enhanced. More starch grains were accumulated in chloroplasts. The root elongation, net photosynthetic rate (Pn), NPQ and rbcS and psbA genes expression were promoted under red light. Yellow light- and green light-illuminated plants grew badly with their lower Rubisco content and Pn value observed, and less starch grains accumulated in chloroplast. However, less influence was noted of light quality on chloroplast structure. Compared with yellow light, the values of ΦPSII, ETR, qP and NPQ of plants exposed to green light were significantly increased, suggesting that green light was beneficial to both the development of photosynthetic apparatus to some extent.     

Light signaling and UV‐B‐mediated plant growth regulation

Light plays an important role in plants’ growth and development throughout their life cycle. Plants alter their morphological features in response to light cues of varying intensity and quality. Dedicated photoreceptors help plants to perceive light signals of different wavelengths. Activated photoreceptors stimulate the downstream signaling cascades that lead to extensive gene expression changes responsible for physiological and developmental responses. Proteins such as ELONGATED HYPOCOTYL5 (HY5) and CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) act as important factors which modulate light‐regulated gene expression, especially during seedling development. These factors function as central regulatory intermediates not only in red, far‐red, and blue light pathways but also in the UV‐B signaling pathway. UV‐B radiation makes up only a minor fraction of sunlight, yet it imparts many positive and negative effects on plant growth. Studies on UV‐B perception, signaling, and response in plants has considerably surged in recent times. Plants have developed different strategies to use UV‐B as a developmental cue as well as to withstand high doses of UV‐B radiation. Plants’ responses to UV‐B are an integration of its cross‐talks with both environmental factors and phytohormones. This review outlines the current developments in light signaling with a major focus on UV‐B‐mediated plant growth regulation.     

Effects of light quality on the chloroplastic ultrastructure and photosynthetic characteristics of cucumber seedlings

To understand how light quality influences plant photosynthesis, we investigated chloroplastic ultrastructure, chlorophyll fluorescence and photosynthetic parameters, Rubisco and chlorophyll content and photosynthesis-related genes expression in cucumber seedlings exposed to different light qualities: white, red, blue, yellow and green lights with the same photosynthetic photon flux density of 100 μmol m^?2 s^?1. The results revealed that plant growth, CO₂ assimilation rate and chlorophyll content were significantly reduced in the seedlings grown under red, blue, yellow and green lights as compared with those grown under white light, but each monochromatic light played its special role in regulating plant morphogenesis and photosynthesis. Seedling leaves were thickened and slightly curled; Rubisco biosynthesis, expression of the rca, rbcS and rbcL, the maximal photochemical efficiency of PSII (Fv/Fm) and quantum yield of PSII electron transport (Ф_PSII) were all increased in seedlings grown under blue light as compared with those grown under white light. Furthermore, the photosynthetic rate of seedlings grown under blue light was significantly increased, and leaf number and chlorophyll content of seedlings grown under red light were increased as compared with those exposed to other monochromatic lights. On the contrary, the seedlings grown under yellow and green lights were dwarf with the new leaves etiolated. Moreover, photosynthesis, Rubisco biosynthesis and relative gene expression were greatly decreased in seedlings grown under yellow and green light, but chloroplast structural features were less influenced. Interestingly, the Fv/Fm, Ф_PSII value and chlorophyll content of the seedlings grown under green light were much higher than those grown under yellow light.     

A Flavin Binding Cryptochrome Photoreceptor Responds to Both Blue and Red Light in Chlamydomonas reinhardtii

Cryptochromes are flavoproteins that act as sensory blue light receptors in insects, plants, fungi, and bacteria. We have investigated a cryptochrome from the green alga Chlamydomonas reinhardtii with sequence homology to animal cryptochromes and (6-4) photolyases. In response to blue and red light exposure, this animal-like cryptochrome (aCRY) alters the light-dependent expression of various genes encoding proteins involved in chlorophyll and carotenoid biosynthesis, light-harvesting complexes, nitrogen metabolism, cell cycle control, and the circadian clock. Additionally, exposure to yellow but not far-red light leads to comparable increases in the expression of specific genes; this expression is significantly reduced in an acry insertional mutant. These in vivo effects are congruent with in vitro data showing that blue, yellow, and red light, but not far-red light, are absorbed by the neutral radical state of flavin in aCRY. The aCRY neutral radical is formed following blue light absorption of the oxidized flavin. Red illumination leads to conversion to the fully reduced state. Our data suggest that aCRY is a functionally important blue and red light-activated flavoprotein. The broad spectral response implies that the neutral radical state functions as a dark form in aCRY and expands the paradigm of flavoproteins and cryptochromes as blue light sensors to include other light qualities.     

Plasticity of photosynthetic processes and the accumulation of secondary metabolites in plants in response to monochromatic light environments: A review

Light spectra significantly influence plant metabolism, growth and development. Here, we review the effects of monochromatic blue, red and green light compared to those of multispectral light sources on the morpho-anatomical, photosynthetic and molecular traits of herbaceous plants. Emphasis is given to the effect of light spectra on the accumulation of secondary metabolites, which are important bioactive phytochemicals that determine the nutritional quality of vegetables. Overall, blue light may promote the accumulation of phenylpropanoid-based compounds without substantially affecting plant morpho-anatomical traits compared to the effects of white light. Red light, conversely, strongly alters plant morphology and physiology compared to that under white light without showing a consistent positive effect on secondary metabolism. Due to species-specific effects and the small shifts in the spectral band within the same color that can substantially affect plant growth and metabolism, it is conceivable that monochromatic light significantly affects not only plant photosynthetic performance but also the “quality” of plants by modulating the biosynthesis of photoprotective compounds.     

Ginkgo biloba retains functions of both type I and type II flowering plant phytochrome

While the photoreceptor systems of flowering plants have been well studied, the origins of these gene families and their functions are only partially understood. To begin to resolve the evolutionary origins of angiosperm photoreceptor function, we have studied the photomorphogenic responses of the early diverging gymnosperm Ginkgo biloba. Here, we describe the effects of continuous white light, red light, far-red light, and blue light on stem length, chlorophyll accumulation, Lhcb mRNA accumulation, and plastid development. Differences in the efficacy of these light regimes on de-etiolation in Ginkgo suggest separate but complementary roles for red and blue light-sensing systems. Additionally, the unique manner in which developmental regulation occurs in Ginkgo reveals a far-red high irradiance response different from both angiosperm and other gymnosperm species. We conclude from these data that Ginkgo contains a functional complement to both flowering plant type I and type II phytochromes, as well as independent blue light-sensing system(s). The implications of these findings are discussed with respect to the evolution of higher plant photoreceptors.     

Genome-wide analysis of light-dependent transcript accumulation patterns during early stages of Arabidopsis seedling deetiolation

Light is among the most important exogenous factors that regulate plant development. To sense light quality, intensity, direction, and duration, plants have evolved multiple photoreceptors that enable the detection of photons from the ultraviolet B (UV-B) to the far-red spectrum. To study the effect of different light qualities on early gene expression, dark-grown Arabidopsis (Arabidopsis thaliana) seedlings were either irradiated with continuous far-red, red, or blue light or received pulses of red, UV-A, or UV-A/B light. The expression profiles of seedlings harvested at 45 min and 4 h were determined on a full genome level and compared with the profiles of dark controls. Data were used to identify light-regulated genes and to group these genes according to their light responses. While most of the genes were regulated by more than one light quality, a considerable number of UV-B-specific gene expression responses were obtained. An extraordinarily high similarity in gene expression patterns was obtained for samples that perceived continuous irradiation with either far-red or blue light for 4 h. Mutant analyses hint that this coincidence is caused by a convergence of the signaling cascades that regulate gene expression downstream of cryptochrome blue light photoreceptors and phytochrome A. Whereas many early light-regulated genes exhibited uniform responses to all applied light treatments, highly divergent expression patterns developed at 4 h. These data clearly indicate that light signaling during early deetiolation undergoes a switch from a rapid, but unspecific, response mode to regulatory systems that measure the spectral composition and duration of incident light.     

Light Quality Regulates Lateral Root Development in Tobacco Seedlings by Shifting Auxin Distributions

Light is an important environmental regulator of diverse growth and developmental processes in plants. However, the mechanisms by which light quality regulates root growth are poorly understood. We analyzed lateral root (LR) growth of tobacco seedlings in response to three kinds of light qualities (red, white, and blue). Primary (1°) LR number and secondary (2°) LR density were elevated under red light (on days 9 and 12 of treatment) in comparison with white and blue lights. Higher IAA concentrations measured in roots and lower in leaves of plants treated with red light suggest that red light accelerated auxin transport from the leaves to roots (in comparison with other light qualities). Corroborative evidence for this suggestion was provided by elevated DR5::GUS expression levels at the shoot/root junction and in the 2° LR region. Applications of N-1-naphthylphthalamic acid (NPA) to red light-treated seedlings reduced both 1° LR number and 2° LR density to levels similar to those measured under white light; DR5::GUS expression levels were also similar between these light qualities after NPA application. Results were similar following exogenous auxin (NAA) application to blue light-treated seedlings. Direct [³H]IAA transport measurement indicated that the polar auxin transport from shoot to root was increased by red light. Red light promoted PIN3 expression levels and blue light reduced PIN1, 3–4 expression levels in the shoot/root junction and in the root, indicating that these genes play key roles in auxin transport regulation by red and blue lights. Overall, our findings suggest that three kinds of light qualities regulate LR formation in tobacco seedlings through modification of auxin polar transport.     

Light induction of the Euglena chloroplast protein synthesis elongation factors: relative effectiveness of different wavelength ranges

The abilities of different wavelength ranges of light to promote the increase in the activities of the Euglena chloroplast protein synthesis elongation factors (EFs) during chloroplast biogenesis have been determined. Blue light was far more effective than either green light or red light in increasing the level of chloroplast EF-G, a nuclear encoded gene product. This observation suggests that the induction of EF-Gchl is under the control of the blue photoreceptor that has been identified in Euglena. Blue light was also the most effective wavelength range in facilitating the increase in EF-Ts, a nuclear gene product, and EF-Tu, a chloroplast gene product. However, red light and surprisingly green light were also effective. These results are not consistent with either of the known blue or blue/red photoreceptor systems in Euglena being the sole component involved in the light induction of these two factors and suggest that a green photoresponse may also be important in the development of the chloroplast. The specific activity of the Euglena mitochondrial protein biosynthetic translocase (EF-Gmt) decreased in cells exposed to light. Blue light caused an immediate decline in EF-Gmt activity; whereas, there was a temporal delay in the decrease in EF-Gmt activity when cells were exposed to either red or green light.     

LED不同光质对萝卜愈伤组织诱导、增殖和萝卜硫素含量的影响

以白水萝卜无菌苗及其愈伤组织为实验材料,研究其在LED白、红、黄、蓝、绿和蓝红6种光质下的愈伤诱导和增殖。结果表明：LED不同光质下胚轴愈伤组织的诱导效应不同,诱导率顺序依次为黄光〉红光〉蓝红光〉白光〉蓝光〉绿光;蓝光、黄光和红光有利于子叶愈伤组织的诱导;子叶诱导愈伤组织的效果较下胚轴好;LED红光下愈伤组织的增殖倍数和萝卜硫素含量均为最高。     

不同光质对辣椒叶色黄化突变体光合生理特性的影响研究

以辣椒叶色黄化突变体yl1及其野生型6421为试材,用白光、蓝光、红光、绿光、紫光、黄光和远红光不同光质进行处理,考察其表型、生理及光合特性的变化特征,探究光质对黄叶辣椒植株生长发育的影响。结果显示：(1)蓝光与红光对辣椒幼苗的生长有促进作用,黄光和远红光则会显著抑制幼苗生长,6421生长受不同光质的抑制影响比yl1更大。(2)两个辣椒材料光合色素含量在不同光质下均不同程度降低;6421叶绿素总含量和类胡萝卜素含量在不同光质下均高于yl1,yl1和6421叶片的光合色素含量分别在紫光和黄光下最低。(3)蓝光和绿光能显著提高yl1的净光合速率(P_n),而不同光质处理均显著降低了6421的P_n。(4)紫光处理使yl1的PSⅡ潜在活性(F_v/F_o)和最大光化学效率(F_v/F_m)值均显著降低且显著低于6421,但升高了光化学猝灭系数(qP)和非光化学猝灭系数(NPQ)。(5)蓝光、红光和绿光均能提高辣椒的超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(...     

Combination of Red and Blue Lights Improved the Growth and Development of Eggplant (Solanum melongena L.) Seedlings by Regulating Photosynthesis

The photosynthesis, photomorphogenesis, and photoperiod processes in plants are regulated according to light intensity and quality. The aim of this study was to investigate the effects of different light qualities on eggplant seedlings and determine the best light quality for growth. The seedlings of eggplant cultivar ‘Jingqiejingang’ were grown under light-emitting diodes (LEDs): white (W, the control), red (R), blue (B), and different ratios of B/R lights (B/R = 1/1, B/R = 1/3, B/R = 1/6, B/R = 1/9). The growth parameters, leaf morphology, photosynthetic performance, chlorophyll fluorescence, and the carbon and nitrogen metabolism in the leaves of eggplant seedlings under different LED light treatments were studied. The results showed that the plant height, leaf development, and photosynthetic characteristics were inhibited by red light but elevated by blue light compared with the control. Conversely, the contents of chlorophyll a, chlorophyll b, and carotenoids were all increased by red light, while decreased by blue light significantly. In addition, the contents of carbohydrates and the activities of nitrogen assimilation enzymes were not or little changed by the monochromatic blue and red light. The combined light of red and blue were more beneficial for growth than the monochromatic light, especially B/R = 1/3 light. Under B/R = 1/3 light, the parameter values of plant growth, leaf development, photosynthetic pigments and characteristics, and carbon and nitrogen metabolism were all maximum. Taken together, combined application lights of red and blue are good practice for the cultivation of eggplant seedlings, and LED B/R = 1/3 light was optimum.

     

shl, a New set of Arabidopsis mutants with exaggerated developmental responses to available red, far-red, and blue light

The interaction of light perception with development is the subject of intensive genetic analysis in the model plant Arabidopsis. We performed genetic screens in low white light-a threshold condition in which photomorphogenetic signaling pathways are only partially active-for ethyl methane sulfonate-generated mutants with altered developmental phenotypes. Recessive mutants with exaggerated developmental responses were obtained in eight complementation groups designated shl for seedlings hyperresponsive to light. shl1, shl2, shl5, and shl3 shl4 (double mutant) seedlings showed limited or no phenotypic effects in darkness, but showed significantly enhanced inhibition of hypocotyl elongation in low-white, red, far-red, blue, and green light across a range of fluences. These results reflect developmental hyper-responsiveness to signals generated by both phytochrome and cryptochrome photoreceptors. The shl11 mutant retained significant phenotypic effects on hypocotyl length in both the phyA mutant and phyB mutant backgrounds but may be dependent on CRY1 for phenotypic expression in blue light. The shl2 phenotype was partially dependent on PHYB, PHYA, and CRY1 in red, far-red, and blue light, respectively. shl2 and, in particular, shl1 were partially dependent on HY5 activity for their light-hyperresponsive phenotypes. The SHL genes act (genetically) as light-dependent negative regulators of photomorphogenesis, possibly in a downstream signaling or developmental pathway that is shared by CRY1, PHYA, and PHYB and other photoreceptors (CRY2, PHYC, PHYD, and PHYE).