Research Progress on the Effect of Light on Plant Growth

Xuejing DONG　Liba XU　Miao ZHANG　Ying WANG　Hua ZHU

AbstractLight is one of the important factors affecting plant growth and has an important impact on plant growth and development. In this paper， the effects of light on plant growth， development， and physiological and biochemical functions were reviewed from three aspects： light intensity and light quality on plant biomass， photosynthesis， and chemical components.

Key wordsLight intensity; Light quality; Biomass; Photosynthesis; Chemical composition

Light is one of the important factors affecting plant growth. It is closely related to plant growth and development， photosynthesis， respiration， nutrient absorption and distribution and accumulation of secondary metabolites[1]. In this paper， the current status of the effects of light on plant growth， development and physiological functions was reviewed in combination with factors such as light and biomass， photosynthesis and chemical components.

Biomass

The way plants adapt to changing habitats is manifested in phenotypic plasticity and genetic variation， which improve their own viability[2]. Under different light and water conditions， plants will change leaf area， specific leaf area， transpiration， net photosynthetic rate and water use efficiency by allocating biomass to various organs[3]. To meet the needs of photosynthesis， leaves are the organ most sensitive to light intensity[4]. Light intensity will change the activity of plant-related enzymes， affect the accumulation and distribution of biomass， and then change the internal structure and external shape of plant organs[5].

Cheng et al.[6] evaluated the changes of gene expression during the formation of adventitious roots of lotus under different light intensities （dark， 5 000 lx and 20 000 lx）， and used high-throughput marker sequencing to observe gene expression profiles， and found that under the three different light intensities， 1 739 ， 1 683 and 1 462 up-regulated genes and 1 533， 995 and 834 down-regulated genes had a greater impact on the formation of adventitious roots. Darkness inhibited adventitious root growth， while the high-intensity light promoted the development of adventitious root primordia. Li et al.[7] observed the effects of different light intensities [25， 50， 75 and 100 μmol/（m·s）] on Dendrobium officinale test-tube plantlets， and found that the light intensity of 75 μmol/（m·s） could significantly increase the stem diameter and fresh weight of single plantlets， and the average root diameter， total root volume and total root tip number and other biomass indices of single plantlets. Cheng et al.[8] used four light intensities （25%， 50%， 75% and 100% of natural light， respectively） to treat Juglans regia L.f. luodianense seedlings， and found that 50% and 75% natural light could significantly increase the height， leaf area and biomass distribution of each part （root， stem and leaf）， and improve the chlorophyll content， indicating that light intensity has obvious regulatory effects on the morphology， biomass distribution and physiological characters of J. regia L.f. luodianense seedlings.

Xia et al.[9] treated Viburnum japonicum seedlings with different shading degrees （30% and 60%）. The results showed that the growth of seedlings was severely inhibited under full light conditions， and compared with full light conditions， the specific leaf weight of leaves decreased with the weakening of the light intensity， indicating that shading treatment could speed up the growth rate of seedlings， and 60% shading treatment was more suitable for the growth of the plant.  Huang et al.[10] treated the cuttings of Clerodendrum japonicum with three light intensities （17.8%， 36.1% and 100%）， and found that shading treatment was beneficial to the accumulation of biomass such as seedling height， leaf area and root length， and the light intensity of 17.8% was more suitable for the growth of C. japonicum. Hao et al.[11] investigated the effects of different light intensities and nitrogen application rates on the growth and nitrogen content of Bletilla striata seedlings， and found that under the conditions of 40% natural light intensity and nitrogen application rate （500.0 mg/kg）， the leaf area and nitrogen content of whole plant of B. striata seedlings were the largest， indicating that the interaction of light and nitrogen under shading and nitrogen fertilizer application had a significant effect on the leaf area and nitrogen content of B. striata and could promote the growth of B. striata.

Ohashi-Kaneko et al.[12] found that in the dark environment， the irradiation of both red light and blue light on spinach could accelerate the leaf expansion of spinach. Li et al.[13-14] found that red light and far-red light had a great influence on the growth and morphological structure of lettuce， which was manifested in increasing the leaf area of lettuce and improving the fresh and dry weight of lettuce. Li et al.[15] found that light quality （yellow light， purple light） could promote the early elongation speed of tobacco leaves， red light could promote leaf development， and blue light could inhibit leaf development. Gao et al.[16] used different proportions of light qualities （blue， red light） to intervene pumpkin seedlings and found that blue light and red light had opposite effects on seedling stems， showing inhibition and promotion respectively， and blue light extended the seedling cultivation cycle， while pumpkin seedlings cultivated with red light had thin stems， which reduced the quality of grafting. It showed that the use of the two light qualities alone was not suitable for the normal development of pumpkin seedlings， while with the combined intervention of red and blue light （red∶blue=8∶1）， the pumpkin seedlings had a well-proportioned shape and the best growth quality. Tian et al.[17] used film covering with three light qualities （purple， blue and red） to observe the growth of sweet pepper plants and found that the stems of sweet pepper plants after red treatment were the thickest， but the plant height was shorter， while those treated with blue light quality were the thinnest， but the plant height was higher， indicating that light qualities had a significant effect on the growth of sweet pepper plants.

Physiological Functions

Photosynthetic pigments

Photosynthetic pigments can absorb， transmit and convert light energy， and are the material basis for plants to perform photosynthesis. The content of photosynthetic pigments can directly affect the photosynthetic rate of leaves[18]. Chlorophyll is a kind of photosynthetic pigment， and its absorption peak is mainly in the red light region. Studies have found that different light qualities and light intensities have different effects on the chlorophyll content of plants. Blue light mostly exhibits an inhibitory effect， and high light intensity is not conducive to the production and accumulation of chlorophyll.

Guo et al.[19] studied the effects of three light intensities [10， 30 and 50 μmol/（m·s）] and four phosphorus concentrations （0.005， 0.02， 0.1 and 0.6 mg/L） on the growth of C. oligoclora Kütz. It was found that the greater the light intensity， the lower the value of the chlorophyll fluorescence parameter Fv/Fm. Compared with phosphorus concentration， light intensity had a greater impact on the growth of C. oligoclora. Wang et al.[20] set four light intensity levels （5%-10%， 30%-35%， 70%-75% and 100%） to treat Uncaria seedlings by shading， and found that the content of chlorophyll in seedlings was negatively correlated with light intensity. The light intensity of 5%-10% was most favorable for the accumulation of chlorophyll， while the light intensity of 70%-75% was most favorable for the accumulation of biomass， indicating that light intensity had different effects on different parts of the plant. Zhu et al.[21] found that there was a parabolic relationship between light intensity and the relative content of chlorophyll in Phedimus aizoon. Light intensities of 300 and 600 μmol/（m·s） had the strongest promoting effect on chlorophyll synthesis， and the chlorophyll content was the highest. Strong or too weak light was not conducive to chlorophyll accumulation. Xu et al.[22] set a total of six light intensities of 0， 1 000， 3 000， 5 500， 7 000 and 9 000 lx to cultivate Chlorella vulgaris indoor. The results showed that with the passage of culture time， the content of chlorophyll a in C. vulgaris first increased and then decreased， and 5 500 lx was the most favorable for the growth of C. vulgaris. Cui et al.[23] treated the leaves with four shading degrees （0， 50%， 70%， and 90%） to explore the response of leaves to light， and found that the leaves in the 50% and 70% treatments had the highest net photosynthetic rate and lower Fv/Fm under full light conditions， indicating that moderate shading could promote the growth and development and photosynthesis of B. striata. Zhong et al.[24] treated Tradescantia virginiana L. with four light intensities （5%， 30%， 65% and 100% of the natural light intensity， respectively）， and found that the value of Fv/Fm was the lowest under 100% light intensity， and the highest under 65% light intensity. The photoinhibition effect on T. virginiana increased with the increase of light intensity.

Yu et al.[25] set up six different combinations of red， blue and composite red and blue light quality （supplementary light groups） and no supplementary light group to treat summer black grapes， and found that the contents of chlorophyll a， chlorophyll b and total chlorophyll in the leaves treated with red light with a wavelength of 630 nm was the highest， and the content of chlorophyll in the leaves treated with blue light with a wavelength of 460 nm was the lowest. The photosynthetic accumulation of leaves in the six supplementary light quality groups was higher than that of the non-supplementary light group， indicating that different light qualities could promote photosynthetic accumulation， and red light was more conducive to promoting chlorophyll synthesis. Wang et al.[26] also found that the chlorophyll content of leaves treated with red light was significantly higher. Xu et al.[27] found that red light could promote the increase of chlorophyll content in lettuce leaves， blue light had an inhibitory effect， and yellow light had the strongest promoting effect. Zhang et al.[28] treated 5-year-old Asarum using sun shelters having different light qualities formed with different colors of filter films. The results showed that when the transmittance of red light and blue light was high and the ratio was close to 1∶1， the content of photosynthetic pigments was the highest; and when the transmittance ratio of red light and blue light exceeded 3∶1 and the transmittance of red light was as low as 18.7%， the content of photosynthetic pigments was the lowest. Yang et al.[29] found that the chlorophyll content and net photosynthetic rate in the new shoot leaves of Jinqiu sugar orange treated with monochromatic blue light and red light were reduced， while the red-blue composite light （1∶1） could enhance the photosynthesis of leaves， which was beneficial to balanced distribution of materials for stems and leaves.

Photosynthetic capacity

Photosynthesis is the prerequisite for the production and accumulation of photosynthetic substances in plants. When a plant has stronger photosynthetic capacity， it can absorb more nutrients， and it can provide more energy for its growth. Studies have found that red and blue mixed light is more conducive to enhancing the photosynthetic rate than monochromatic light， and too strong or two weak or even no light condition reduces photosynthetic rate， which leads to slow plant growth.

Liu et al.[30] treated Syzygium hancei seedlings with four light transmittance （24.9%， 48.6%， 72.3%， and 100.0%， respectively）. The results showed that high light transmittance inhibited the net photosynthetic rate and daily average stomatal conductance of seedlings， and promoted the maximum net photosynthetic rate， light compensation point， light saturation point and chlorophyll content. Zhao et al.[31] set three light intensities （full light， 30% shading and 50% shading） to treat the mother plants of Juniperus chinensis ‘Plumosa Aurea’ for 90 d， and found that the photosynthetic capacity of the mother plants was the strongest under 30% shading treatment， which could accumulate richer nutrients for new shoots， improve the quality of cuttings and the rooting rate of cuttings. Abudoukeyoumu Abudourezike et al.[32] treated Taraxacum kok-saghyz Rodin with three light intensities： no shade， light shade， and heavy shade， and found that light shading could promote the synthesis of citric acid， total flavonoids， total phenols and other substances in the roots and leaves of T. kok-saghyz， enhance the photosynthetic performance， and increase the accumulation and output of photosynthetic products. Wang et al.[33] used full illumination as a control， and set four light intensities of 20%， 40%， 60%， and 80% shade to treat three-year-old Xinyang Wuyiexian peach. The results showed that shading could relieve the "photosynthetic lunch break" of Xinyang Wuyiexian peach. The 20% shading treatment had the best leaf growth and the highest net photosynthetic rate， while excessive shading treatment did not significantly promote the net photosynthetic rate.

Li et al.[15] found that during the growth and development period of tobacco leaves， the stomatal conductance， intercellular CO concentration and transpiration rate of leaves treated with red， blue and purple films increased， thereby enhancing the net photosynthetic rate. Xu et al.[27] found that red light and yellow light could increase the net photosynthetic rate of Lactuca sative leaves， while blue light could reduce it， which might be related to the low content of red light in the spectrum of blue light emission. Wei et al.[34] treated 3-year-old Panax ginseng with different light qualities， and found that the mixed light of red and blue could significantly increase the net photosynthetic rate， stomatal conductance， transpiration rate and intercellular CO concentration. Yin[35] treated parsley with light-emitting diodes （LEDs） of different colors and found that the photosynthetic rate， transpiration rate and stomatal conductance of parsley leaves were the highest under red and blue light （6∶1）， and the lowest under blue light.

Chemical Composition

Flavonoids

Flavonoids are widely present in plants and are important secondary metabolites. Many scholars believe that the anabolic pathway of flavonoids in plants is the phenylpropane pathway[36-38]. Phenylalanine is converted by the action of phenylalanine ammonia lyase （PAL） into cinnamic acid， which is converted by the action of cinnamic acid-4-hydroxylase （C4H） into P-coumaric acid， which then under the action of 4-coumarin-CoA ligase （4CL） produces p-coumaroyl-CoA， which is catalyzed by chalcone synthase （CHS） to form chalcone， which is further converted into isoflavones and flavonols and other flavonoids. Light intensity and light quality may affect the content by affecting the gene expression of the flavonoid synthesis pathway.

Cheng et al.[39] studied the effect of light on the synthesis of flavonoids in grape calli， and set three light intensities of 0， 125 and 250 μmol/（m2·s）. The results showed that the expression of flavonols， anthocyanins and related genes was less affected， while the concentration of flavon-3-ol was more affected， indicating that the effects of light intensity on flavonoids were different. Xu et al.[40] treated potted ginkgo seedlings with a light intensity of 800 μmol/（m·s） at 15 ℃ for 40 d and a light intensity of 500 μmol/（m·s） at 25 ℃ for 20 d. The content of flavonoids in ginkgo significantly increased compared with that before treatment， and some treatment groups showed that the increase of flavonoids had significant light intensity effects and interactive effects of temperature and light intensity. Three kinds of light intensity treatments were given to the cuttings of Tetrastigma hemsleyanum， and the results showed that with the increase of light intensity， the content of total flavonoids in tuberous roots gradually increased， indicating that moderately increasing the light intensity was beneficial to the development of tuberous roots and the accumulation of total flavonoids[41]. Fan et al.[42] set the light intensities weakened by 20%， 40% and 60% and normal light intensity to treat fruiting trees of Rosa roxburghii Tratt and found that with the weakening of the light intensity， the content of flavonoids in R. roxburghii fruit became lower and lower. It was found that the activity of PAL， C4H， 4CL and CHS in the fruit decreased with the weakening of light intensity， indicating that light intensity might affect the content of flavonoids through the phenylpropane pathway. Pacheco et al.[43] studied the effects of different light intensities and light qualities on the activity of PAL in the leaves of Piper nigrum trees， and found that the activity of PAL under the treatments of 50% and 70% of full light was 2.5 times that of full light， and the activity under the blue light treatment was 3.06 times that of the red light treatment， indicating that shading and blue light treatment were beneficial to the increase of PAL activity.

Guo et al.[44] found that monochromatic red light was not conducive to the accumulation of flavonoids in Loropetalum chinense var. rubrum calli， and blue UV-A mixed light and monochromatic blue light were beneficial to the increase of total flavonoids. Tang[45] found that blue light could significantly increase the content of total flavonoids in Medicago sativa sprouts， and white light could significantly increase the content of total flavonoids in Toona sinensis sprouts. Liu et al.[46] found that the total flavonoid content in the leaves of Anji No. 1 family in Zhejiang under blue light treatment was the highest， and it was speculated that it might be related to blue light receptors in the leaves. Li et al.[41] studied the effect of continuous blue light treatment on the synthesis of flavonoids in soybean sprouts， and found that continuous blue light irradiation for 36 h could significantly increase the expression of blue light photoreceptor genes CRY1 and CRY2 in soybean sprout cotyledons， and the expression levels of flavonoid synthesis-related genes PAL， CHS， ANS and IFS increased first and then decreased with the prolongation of irradiation time.

Alkaloids

Xu et al.[48] treated Dendrobium officinale protocorms with four light intensities of 500， 1 000， 2 000， 3 000 and 4 000 lx， and the results showed that the alkaloid content first increased and then decreased with the prolongation of culture time. Except dark culture， other light treatments reached the maximum values of alkaloids at 30 d， and 20-30 d was the period of rapid growth of alkaloids， but the alkaloid accumulation under 3 000 lx light condition was lower than that of other treatments. Therefore， culturing for 30 d under the condition of light intensity of 2 000 lx was conducive to the accumulation of alkaloids in high-quality D. officinale protocorms. Niu et al.[49] set four light intensities of 500， 1 500， 3 000， 4 500 and 6 000 lx to treat tissue culture plantlets of Anoectochilus roxburghii， and found that the content of alkaloids was higher under the conditions of light intensities of 3 500 and 4 500 lx.

Blue light can promote the accumulation of alkaloids in Lycoris radiata seedlings， D. officinale protocorms and D. officinale test-tube plantlets[50-52]. Peng[43] found that red and blue light mixed （1∶2） treatment could significantly increase the content and accumulation of D. nobile alkaloids. Green light can inhibit the accumulation of alkaloids in the protocorms of D. officinale to varying degrees[44]， but could increase the content of total alkaloids in the roots of Aconitum pendulum[54]. Gao et al.[50] found that compared with red light， yellow light and green light， blue light was more conducive to the thickening of D. officinale seedlings and the accumulation of alkaloids.

Phenolic acids

Meng et al.[55] conducted five different light intensity treatments with light transmittance of 100.0%， 82.6%， 60.1%， 37.8% and 14.5% in the growth process of dandelion， and measured the total phenolic acid content. Among the various treatments， the 82.6% light transmittance treatment group had the highest total phenolic acid content， and the 14.5% light transmittance treatment group had the lowest total phenolic acid content. Therefore， in the production and cultivation of dandelion， appropriate use of sunshade net treatment for reducing the light intensity and the light transmittance between 60.1% and 82.6% will help to improve the nutritional quality of dandelion.

Chang et al.[56] found that green light could increase the mass fraction of total ferulic acid in wheat sprouts and promote the conversion of free ferulic acid to bound state; the content of total p-coumaric acid was the highest under yellow light treatment; green light and yellow light could significantly increase the content of total caffeic acid， while the value of white light treatment significantly decreased; green light and yellow light treatments could significantly increase the total content of syringic acid; and blue light， red light and white light could significantly increase the content of total sinapic acid. Li et al.[50] found that the contents of five phenolic acids， quercetin， ferulic acid， kaempferol， isorhamnetin and chlorogenic acid， all reached the highest levels in Fujian Anoectochilus roxburghii and Taiwan Anoectochilus formosanus Hayata under the mixed light of red and blue （2∶1）.

Soluble sugar

Sugar is an important component in plants， and the content of soluble sugar as an intermediate product can reflect the speed of metabolism in the process of growth[58]. Studies have found that the content of soluble sugars in plants treated with red light or with a higher proportion of red light is higher; and within a certain range， a greater light intensity is more conducive to the accumulation and transformation of soluble sugars[59]. However， the effects of light on the accumulation of soluble sugar in plants also differed among different plant species.

Liu et al.[60] treated Piper nigrum cuttings with different light intensities and found that soluble sugars in mature leaves first increased and then decreased with the increase of light intensity. Gong et al.[61] found that the soluble sugar content of Camellia oleifera seedlings was the lowest under the treatment of 100 μmol/（m·s）， and the highest under the treatment of 250 μmol/（m·s）. Lin et al.[62] treated gourd seedlings with different ratios of red and blue light and different light intensities and found that the soluble sugar content of leaves increased with the increase of light intensity. On the 14th d of treatment， the content of soluble sugar in leaves of gourd seedlings treated with mixed light of red and blue （7∶3） with a light intensity of 120 μmol/（m·s） reached the highest value.

Tang[45] found that red/blue （2∶1）， red/blue （7∶1） and red/far red （1∶2） could significantly increase the soluble sugar content of transplanted Anthurium andraeanum seedlings. Li et al.[57] treated the tissue culture plantlets of Fujian A. roxburghii and Taiwan A. formosanus with three light qualities， and found that there was no significant difference in the content of soluble sugar in Fujian A. roxburghii， while for Taiwan A. formosanus， the content of soluble sugar was larger with composite light than with white light， the highest with the red-blue composite light （1∶2）， followed by the red-blue composite light （2∶1）. Liang et al.[50] treated hydroponic lettuce with four light qualities， i.e.， mixed light with the ratio of red and blue light at 4∶1， 1∶2， and full red light and full blue light. They found that a high proportion of red light could promote the accumulation of soluble sugar in lettuce， but the light quality with the ratio of red to blue light at 4∶1 achieved the best treatment effect. Xie et al.[63] found that red light， white light and blue light supplementation could significantly increase the content of soluble sugar in dragon fruit plants， and blue light supplementation had the best effect. Xie et al.[64] studied the effects of white light， red light and blue light on Sarcandra glabra seedlings， and found that red light was not conducive to the accumulation of soluble sugar， and blue light could also reduce the content of soluble sugar in leaves.

Other ingredients

Ma et al.[56] studied the effects of temperature and light on the accumulation of lutein in Chlorella FZU60 under mixed nutrient conditions， and the results showed that the yield of lutein was lower under the strong light of 750 μmol/（m·s）， indicating that the low light intensity was more suitable for the accumulation of lutein. Wang et al.[57] analyzed the effects of light intensity changes on the accumulation of various active components in the roots of Astragalus memeranaceus by ultra-high performance liquid chromatography. They found that reduced light intensity had an increased comprehensive effect on the main active components of A. memeranaceus; dark conditions were conducive to the accumulation of campanulin， calycosin and astragaloside A; and low light was conducive to the accumulation of cycloastragenol， while high light was conducive to the accumulation of ononin. It indicated that different light intensities are suitable for the accumulation of different medicinal components. Kazufumi et al.[67] found that tomato varieties with high ascorbic acid and low ascorbic acid cultured in vitro， the content of ascorbic acid increased with the increase of light intensity and blue LED light. Giuseppina et al.[68] measured the growth and total lipid content of Juniperus chinensis under four light intensities of 2 500， 5 000， 7 500 and 10 000 lx. The results showed that the growth of J. chinensis was significantly different among the four levels of treatments， and the total fat content decreased with the light intensity decreasing. Yang et al.[69] set a total of 13 light intensity gradients from 2 to 2 011 lx， and used HPLC to investigate the effects of different light intensities on the content of atractylodin. The results showed that with the increase of light intensity， atractylodin showed a downward trend overall， and the degradation rate showed an upward trend， but after the light intensity reached 1 021 lx， the degradation rate was relatively stable， indicating that the light intensity had a significant effect on the content of atractylodin.

Ren et al.[70] used three kinds of LED mixed light qualities to treat Begonia fimbristipula. The results showed that treatment 60% red light+20% blue light+20% green light could significantly increase the accumulation of terpenes and reduce the proportion of aldehydes in aroma substances and the content of β-carotene; treatment 60% red light+30% blue light+10% green light increased the content of total anthocyanins; and treatment 70% red light+20% blue light+10% green light increased the accumulation of β-carotene and the antioxidant activity of plant leaf extracts.

Summary and Prospect

At present， the research on the effects of light on plant growth and morphogenesis mainly focuses on the selection of light source， the period of light， the proportion of light quality and light intensity[71]. The growth and development and physiological functions of most plants are affected by changes in light intensity and light quality. Too high or too low light intensity is not conducive to plant growth and metabolism. Different plants have different degrees of sensitivity to light， and different monochromatic light or mixed light in different proportions have different degrees of influence on all aspects of plant growth. Therefore， it is necessary to obtain the light conditions suitable for plant growth through experiments.

References

[1] WANG XD， WANG YY， ZHENG XC， et al. Research progress on the effect of artificial supplementary light on the growth and development of facility horticultural crops[J]. Northern Horticulture， 2019（20）： 117-124. （in Chinese）.

[2] CHENG XR， XING WL， YUAN HJ， et al. Phenotypic plasticity of Illicium lanceolatum in response to varied light environments[J]. Acta Ecologica Sinica， 2019， 39（6）： 1935-1944. （in Chinese）.

[3] ANDREA MOJZES， KALAPOS T， VIRGH K. Plasticity of leaf and shoot morphology and leaf photochemistry for Brachypodium pinnatum （L.） Beauv. growing in contrasting microenvironments in a semiarid loess forest-steppe vegetation mosaic[J]. Flora， 2015， 198（4）： 304-320.

[4] LU D， WANG GG， YAN Q， et al. Effects of gap size and within-gap position on seedling growth and biomass allocation： Is the gap partitioning hypothesis applicable to the temperate secondary forest ecosystems in Northeast China[J]. Forest Ecology and Management， 2018（429）： 351-362.

[5]  LIU C， TIAN T， LI S， et al. Growth response of Chinese woody plant seedlings to different light intensities[J]. Acta Ecologica Sinica， 2018， 38（2）： 518-527. （in Chinese）.

[6] CHENG L， HAN Y， ZHAO M， et al. Gene expression profiling reveals the effects of light on adventitious root formation in lotus seedlings （Nelumbo nucifera Gaertn.）[J]. BMC Genomics， 2020， 21（1）： 707.

[7] LI W， ZHENG JR， MO ZW， et al.  Effect of light intensity on seedling growth and physiological characteristics of Dendrobium officinale Kimura et Migo in vitro[J]. Chinese Journal of Tropical Crops， 2014， 35（1）： 121-125. （in Chinese）.

[8] CHENG J， LIU JM， WANG D， et al. Plastic response of the karst endemic plant Juglans regia L.f. luodianense seedings to light intensity[J]. Chinese Journal of Applied & Environmental Biology， 2021， 27（1）： 23-30. （in Chinese）.

[9] XIA YF， LI RJ， YANG ZJ， et al. Effect of light intensity on growth and physiological characteristics of Viburnum japonicum seedling[J]. Journal of Zhejiang Forestry Science and Technology， 2020， 40（3）： 16-21. （in Chinese）.

[10] HUANG WY， FENG ZJ. Effect of light intensity on the growth and photosynthetic characteristics of Clerodendrum japonicum[J]. Guangdong Forestry Science and Technology， 2020， 36（4）： 96-101. （in Chinese）.

[11] HAO YH， FANG RP， WANG R， et al. Effects of light intensity and nitrogen application on growth and nitrogen content of Bletilla striata seedlings[J]. Journal of Southwest Forestry University： Natural Science， 2020， 41（4）： 1-8. （in Chinese）.

[12] OHASHI-KANEKO K， TAKASE M， KURATA K. Low-light irradiation at the beginning or the end of the daily dark period accelerates leaf expansion and growth in Spinacia oleracea L.[J]. Environment Control in Biology， 2010， 48（4）： 161-173.

[13] LI L， TONG YX， LI J， et al. Effect of different combinations of light wavelengths on growth and energy use efficiency of lettuce[J]. Journal of Northwest A&F University： Natural Science Edition， 2020， 48（9）： 114-120. （in Chinese）.

[14] QIAN L， KUBOTA C. Effects of supplemental light quality on growth and phytochemicals of baby leaf lettuce[J]. Environmental & Experimental Botany， 2009， 67（1）： 59-64.

[15] LI JY， XU CH， CUI MK， et al. Effects of different light quality on tobacco leaf growth and chlorophyll fluorescence parameters[J]. Jiangsu Agricultural Sciences， 2015， 43（11）： 140-145. （in Chinese）.

[16] GAO JM， XU LQ， QU T， et al. Effect of light quality and photoperiod on the growth of pumpkin seedlings [J]. Journal of Chinese Agricultural Mechanization， 2016， 37（12）： 78-82. （in Chinese）.

[17] TIAN FM， MI QH， TAYIRJAN · ABDURAHMAN， et al. Effects of different color films on facility environment and growth， development， yield and quality of sweet pepper[J]. Shandong Agricultural Sciences， 2013， 45（12）： 35-39. （in Chinese）.

[18] ZHENG J， HU MJ， GUO YP. Regulation of photosynthesis by light quality and its mechanism in plants[J]. Chinese Journal of Applied Ecology， 2008（7）： 1619-1624. （in Chinese）.

[19] GUO LL， ZHOU WC， ZHOU QC， et al. Effects of light intensity and phosphorus concentration on the growth of Cladophora oligoclona[J]. China Environmental Science， 2015， 35（7）： 2153-2159. （in Chinese）.

[20] WANG JJ， JI LL， DENG XH， et al. Effects of light intensity on growth and content of active components of Uncaria rhynchophyll[J]. China Journal of Chinese Materia Medica， 2019， 44（23）： 5118-5123. （in Chinese）.

[21] ZHU XQ， YANG LQ， ZENG H， et al. Effects of different illumination intensity conditions on morphological and physiology characteristic of Sedum aizoon L.[J]. Journal of Central South University of Forestry & Technology， 2015， 35（6）： 98-102. （in Chinese）.

[22] XU H， JI DB， CUI YJ， et al. Effects of different light intensity on the growth of Chorella vulgaris[J]. Microbiology， 2016， 37（5）： 1027-1034. （in Chinese）.

[23] CUI B， ZHOU YR， WANG XM， et al. Study on the photosynthetic and physiological characteristics of Bletilla striata under different light intensities[J]. Journal of Henan Agricultural University， 2020， 54（2）： 276-284. （in Chinese）.

[24] ZHONG J， WU SL， YU W， et al. Effects of different light intensity on pigment and chlorophyll fluorescence of Setcreasea purpurea[J]. Guizhou Agricultural Sciences， 2020， 48（9）： 1-5. （in Chinese）.

[25] YU YANG， LIU S， LI CX， et al. Effects of LED light quality on the photosynthetic properties and physiological indexes of ‘Summer black’ grape [J]. Journal of Fruit Science， 2015， 32（5）： 879-884. （in Chinese）.

[26] WANG XX， ZHAO WD， GUO XW， et al. Effects of supplemental lighting with different light quality on the shoot growth and physiology of ‘Kyoho’ grape growing in greenhouse for delay[J]. Northern Fruits， 2009（3）： 3-5. （in Chinese）.

[27] XU L， LIU SQ， QI YD， et al. Effect of light quality on leaf lettuce photosynthesis and chlorophyll fluorescence[J]. Chinese Agricultural Science Bulletin， 2007（1）： 96-100. （in Chinese）.

[28] ZHANG M， WANG ZQ， QUAN XZ， et al. Effects of light quality on growth and photosynthetic physiology characteristics of Asarum heterotropoides Fr. schmidt var. mandshuricum （Maxim） kitag[J]. Northern Horticulture， 2022（3）： 107-117. （in Chinese）.

[29] YANG C， LIU MZ， LI Q， et al. Effects of different light-emitting diode （ LED ） light quality on growth， development and photosynthetic characteristics of Jinqiu Shatangju seedlings[J]. Acta Agriculturae Zhejiangensis， 2022， 34（1）： 89-97. （in Chinese）.

[30] LIU JC， ZHAO LJ， ZHU LQ， et al. Effects of shading on photosynthetic characteristics of Syzygium hancei seedlings [J]. Guangxi Sciences， 2020， 22（3）： 11-19. （in Chinese）.

[31] ZHAO XZ， GAO L， JIA GX. Effects of light treatment on cutting quality of Juniperus chinensis ‘Plumosa Aurea’[J]. Journal of Beijing Forestry University， 2020， 42（8）： 132-140. （in Chinese）.

[32] ABUDOUKEYOUMU·ABUDOUREZIKE， GAO Q， XU L， et al. Effects of shading on the physiological characteristics of Taraxacum koksaghyz Rodin[J]. Xinjiang Agricultural Sciences， 2020， 57（11）： 2126-2134. （in Chinese）.

[33] WANG Z， ZHU JM， YAN TF， et al. Effects of different light illumination on leaf growth and photosynthesis of Xinyang Wuyuexian[J]. Jiangsu Agricultural Sciences， 2021， 49（18）： 134-138. （in Chinese）.

[34] WEI BX， WU AX， XU RM， et al. Effects of different light quality supplemental light treatments on photosynthesis and yield of ginseng[J]. Journal of Agricultural Science Yanbian University， 2021， 43（1）： 7-17. （in Chinese）.

[35] YIN J. Effects of light quality on photosynthetic pigments and photosynthetic fluorescence characteristics of Apium graveolens leaves[J]. Jiangsu Agricultural Sciences， 2018， 46（4）： 116-119. （in Chinese）.

[36] PAN JQ， TONG XR， GUO BL. Progress of effects of light on plant flavonoids[J]. China Journal of Chinese Materia Medica， 2016， 41（21）： 3897-3903. （in Chinese）.

[37] CHEN SY， GU MR， SHU HR. Advances in research on flavonoids in Ginkgo biloba leaf[J]. Scientia Silvae Sinicae， 2000， 36（6）： 110-115. （in Chinese）.

[38] WINKEL-SHIRLEY B. Biosynthesis of flavonoids and effects of stress[J]. Current Opinion in Plant Biology， 2002， 5（3）： 218-223.

[39] CHENG J， YU K， ZHANG M， et al. The effect of light intensity on the expression of leucoanthocyanidin reductase in grapevine calluses and analysis of its promoter activity[J]. Genes （Basel）， 2020， 11（1156）： 1-18.

[40] XU Y， WANG HL， WANG GB， et al. Effects of temperature and light intensity on lfavonoid biosynthesis of ginkgo （Ginkgo biloba L.） leaves[J]. Journal of Central South University of Forestry & Technology， 2016， 36（4）： 30-34. （in Chinese）.

[41] XU HL， LIU JM， FAN XF， et al. Effects of different light intensity on growth and total flavonoids of Tetrastigma hemsleyanum[J]. Modern Chinese Medicine， 2020， 22（11）： 1866-1870. （in Chinese）.

[42] FAN WG， PAN XJ， HE CL， et al. Accumulation of sugar and flavonoids as well as their association with changes of light intensity during fruit development of Rosa roxburghii[J]. Scientia Agricultura Sinica， 2021， 54（24）： 5277-5289. （in Chinese）.

[43] PACHECO FV， ALVARENGA ICA， JUNIOR PMR， et al. Growth and production of secondary compounds in monkey-pepper （Piper aduncum L.） leaves cultivated under altered ambient light[J]. Australian Journal of Crop Science， 2014， 8（11）： 1510-1516.

[44] GUO PY， DENG SY， ZHANG YF， et al. Effect of different light quality on callus growth and flavonoids content of two Loropetalum chinense plants[J]. Acta Botanica Boreali-Occidentalia Sinica， 2022， 42（1）： 118-126. （in Chinese）.

[45] TANG L. Regulation and mechanism of LED light quality in plant tissue culture and sprouts cultivation[D]. Nanjing： Nanjing Agricultural University， 2013. （in Chinese）.

[46] LIU Y， QIN J， ZHOU MM， et al. Influence of light quality and genetype on flavonoid accumulation in the leaves of Cyclocarya paliurus[J]. Journal of Nanjing Forestry University： Natural Science Edition， 2018， 42（3）： 99-104. （in Chinese）.

[47] LI N， ZHANG XY， TIAN JY， et al. Effect of blue light continuous illumination on flavonoid synthesis in soybean sprouts[J]. Soybean Science， 2017， 36（1）： 51-59. （in Chinese）.

[48] XU BQ， CUI YY， GUO C， et al. Dynamic variation of biomass and content of polysaccharide and alkaloid in protocorm like bodies from Dendrobium officinale at different light intensities and incubation time[J]. Chinese Traditional and Herbal Drugs， 2012， 43（2）： 355-359. （in Chinese）.

[49] NIU H， WEI KH， XU Q， et al. Effects of different illuminances on growth， physiological characteristics， and medicinal components of Anoectochilus roxburghii[J]. Journal of Plant Resources and Environment， 2020， 29（1）： 26-36， 43. （in Chinese）.

[50] GAO TT， SI JP， ZHU YQ， et al. Effects of light quality and germplasm on growth and effective ingredients of Dendrobium officinale germchit[J]. China Journal of Chinese Materia Medica， 2012， 37（2）： 198-201. （in Chinese）.

[51] LIN XP， LAI ZX. Effect of light quality on the proliferation of protocorm and active ingredient contents of Dendrobium officinale[J]. Chinese Journal of Tropical Crops， 2015， 36（10）： 1796-1801. （in Chinese）.

[52] LI QZ， CAI YM， YANG Z， et al. Effects of the quality of LED light on the growth， physiological characteristics， and the accumulation of alkaloids in Lycoris radiata[J]. Chinese Journal of Applied & Environmental Biology， 2019， 25（6）： 1414-1419. （in Chinese）.

[53] PENG JB. Effects of different light quality on the growth and effective components of Dendrobium nobile[J]. Journal of Fujian Forestry Science and Technology， 2015， 42（4）： 67-71. （in Chinese）.

[54] DONG L， QUAN HF， SHEN HK， et al. Effects of light spectrum on contents of alkaloids in Radix Aconiti[J]. Research and Practice on Chinese Medicines， 2009， 23（5）： 17-19. （in Chinese）.

[55] MENG YH， XIE XY， ZHANG XC. Effect of different light intensities on nutrition quality of Taraxacum[J]. Journal of Beijing University of Agriculture， 2020， 35（3）： 40-43. （in Chinese）.

[56] CHANG JW， YANG RQ， WANG P， et al. Effects of light spectrums on growth and phenolics accumulation of wheat seedlings for food[J]. Journal of the Chinese Cereals and Oils Association， 2021， 36（12）： 13-20. （in Chinese）.

[57] LI Q， WU D， WU YN， et al. LED light quality affects physiological characteristics and metabolites of Anoectochilus roxburghii and A. formosanus in vitro[J]. Journal of Nanchang University： Natural Science， 2021， 45（1）： 56-62. （in Chinese）.

[58] SHI AQ. Study on leaf of tissue culture and plantlet regeneration system of Loropetalum chinense var. Rubrum[D]. Changsha： Hunan Agricultural University， 2015. （in Chinese）.

[59] JIANG XT， LIN BY， LIN YZ. Effect of weak light stress on growth and physiological and biochemistry characteristics of loofah seedlings[J]. Northern Horticulture， 2015（9）： 14-18. （in Chinese）.

[60] LIU LT， ZU C， YU H， et al. Effects of different light intensities on photosynthesis and flowering of pepper cutting seedlings[J]. Chinese Journal of Tropical Crops， 2019， 40（8）： 1515-1521. （in Chinese）.

[61] GONG HE， YAO XH， WU PF， et al. Effects of different LED intensities on the physiological and biochemical characteristics of oil-tea camellia seedlings[J]. Guihaia， 2019， 39（12）： 1599-1604. （in Chinese）.

[62] LIN K， HUANG Z， LIN BY， et al. Effect of light intensity and the ratio of red to blue light on growth and some physiological and biochemical indices of Lagenaria siceraria （Molina） Standl.[J]. Acta Botanica Boreali-Occidentalia Sinica， 2017， 37（3）： 517-525. （in Chinese）.

[63] XIE ZM， CAI YJ， YU RY， et al. Effects of different supplemental light qualities on physiological characteristics， flowering and fruiting of pitaya stem [J]. Guihaia， 2022， 42（2）： 191-198. （in Chinese）.

[64] XIE DJ， LI JW， YE YJ， et al. Effects of light quality on growth， and physiological and biochemical traits of Sarcandra glaba seedlings[J]. Acta Prataculturae Sinica， 2020， 29（8）： 104-115. （in Chinese）.

[65] MA R， ZHANG Z， HO SH， et al. Two-stage bioprocess for hyper-production of lutein from microalga Chlorella sorokiniana FZU60： Effects of temperature， light intensity， and operation strategies[J]. Algal Research， 2020（52）： 102-119.

[66] WANG Y， LIU Y， LIU J， et al. Effect of light intensity on the contents of main secondary metabolites in Astragalus[J]. Chinese Journal of Applied & Environmental Biology， 2017， 23（5）： 928-933. （in Chinese）.

[67] ZUSHI K， SUEHARA C， SHIRAI M. Effect of light intensity and wavelengths on ascorbic acid content and the antioxidant system in tomato fruit grown in vitro[J]. Scientia Horticulturae， 2020： 274.

[68] FEBRIENI VN， FEBRIENI VN， SEDJATI S， et al. Optimization of light intensity on growth rate and total lipid content of Chlorella vulgaris[J]. IOP Conference Series： Earth and Environmental Science， 2020， 584（1）： 012-040.

[69] YANG D， WANG K， ZHAO J. Effect of illumination condition on the content of atractylodin in Rhizoma Atractylodis[J]. China Pharmacist， 2020， 23（4）： 747-749. （in Chinese）.

[70] REN J， GUO SS， SHEN YZ. Effects of LED light quality on the accumulation of essential oils and phenols in Gynura bicolor DC[J]. Manned Space Flight， 2014， 20（4）： 386-392. （in Chinese）.

[71] WANG J， LU W， TONG Y， et al. Leaf morphology， photosynthetic performance， chlorophyll fluorescence， stomatal development of lettuce （Lactuca sativa L.） exposed to different ratios of red light to blue light[J]. Frontiers in Plant Science， 2016（7）： 250-259.

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