| Light is one of the most important environmental factors, which is the sole energy source of plant growth and development, and also some external signal of plant life cycle, affecting their growth, development and metabolism. Plants are empowered with an array of photoreceptors controlling diverse responses to light parameters, such as spectrum, intensity, direction, duration:the red and far red absorbing phytochromes, the blue and UV-A light absorbing cryptochromes, phototropins, and the other implied photorecepeors, absorbing in UV-A and green regions. Spectral light changes evoke different morphogenetic and photosynthetic responses that can vary among different plant species Many studies about photo-response were done in recent, but many questions about effects on high plants still were not understood.In this study, seedlings of cherry tomato (Lycopersicon esculentum var. cerasiforme) (provided by Taiwan farmers Co.), which developed two leaves after germination, were transplanted and grown in plastic pots containing a mixture of peat and vermiculite (3:1, v/v) under light treatments. They were irrigated by Hoagland nutrient water, and other environmental factors were controlled. The new fourth-generation high-brightness and high-power light emitting diodes (LED) were used as electric source. We studied that effects of LED light on growth and photosynthesis of cherry tomato seedlings. Main research results were as follows:Growth and photosynthesis of cherry tomato seedling were investigated under seven light qualities:fluorescence lamp (white light, CK), red, blue, yellow, green and purple LEDs (Z), red, blue and green LEDs (RBG), red, blue and yellow LEDs (RBY), red, blue and purple LEDs (RBP), red, blue, yellow and purple LEDs (RBYP) and red and blue LEDs (RBG) under the same photosynthetic photon flux density (PPFD) about 50 μmol m-2 s-1 for 35 days. Plant height, stem diameter and leaf area had no significant difference between RB and other treatments. Namely, supplement light based on RB had no significant effect on photomorphology of plant. Besides the Z treatment, plant fresh weight of other treatments was greater than that under RB. The biomass distribution was controlled by light quality. Ratio of root and shoot was the greatest under RB, and the least under RBP, followed by RBG. Furthermore, content of photosynthetic pigments was significantly different under different light treatments. Photosynthetic pigment content was almost the least under RB, and the most under Z. Moreover, the light compensation point (LCP), the apparent quantum efficiency (AQY) and net photosynthetic rate (Pn) of leaves regulation by light quality, Pn and AQY were significantly higher under RBYP than those of other treatments, and LCP was greater under RBG and RB Y than that under RB, while less than that under CK and Z. Light quality also affected light energy distribution of photosystemⅡ (PSII).qp was the least under RB, but qN was the least under Z and RBP, and Fv/Fm was no significant difference among light treatments. Distribution ratio of carbohydrate in cherry tamato leaves was significantly higher under RB than that of other treatment. Compared with the control, distribution ratio in root is no significant difference under other treatment, about 50% carbohydrates was accumulated in the roots, while the distribution ratio in leaf and stem is about 1:1. However, carbohydrates were significantly higher under CK and Z than that of other treatments.The growth, photosynthetic characteristics and photosynthetic organs of cherry tomato seedlings were investigated under different light intensity red and blue LED light. The light treatments was designated as 50μmol m-2 s-1 red and blue LED light (RB50), 150 μmol m-2 s-1 red and blue LED light (RB150),200 μmol m-2 s-1 red and blue LED light (RB200),300 μmol m-2 s-1 red and blue LED light (RB300),450 μmol m-2 s-1 red and blue LED light (RB450) and 550 μmol m-2 s-1 red and blue LED light (RB550). The results showed that fresh weight and dry weight were increased with light intensity increased, however, when light intensity was more than 300 μmol m-2 s-1, the fresh and dry weight were no longer increased with light intensity increased, and up to 550 μmol m-2 s-1, the fresh and dry weight were reduced. Leaf area was less under hight light than that of low light, and height, internode of plant was higher under low light than those of hight light, while stem diameter was thinner under low light than that of high light. Furthermore, the differences of plant height, stem diameter and leaf area was more signifant with the time treated. Moreover, CAT activity and MDA content was reduced with light intensity increased, but MDA content had no significant effects by light intensity. POD activity was increaced with light intensity increased. SOD activity was the highest under middle light intensity. However, CAT, SOD, POD activity and MDA content had an inflection point when light intensity was 300μmol m-2 s-1. In the other sides, the content of photosynthetic pigments was more under low light than that of high light, and there were no significant differences in photosynthetic pigments among RB300, RB450 and RB550. Net photosynthetic rate increased with the increase of light intensity, photosynthate was also increases with the increase of light intensity, but photosynthate of the RB550 treatment was a significant reduction. Fv/Fm and qN were significantly greater under RB50 than other treatments. Moreover, content and size of starch granules in chloroplast were significantly different between light treatments. At the light intensity to 300 μmol m-2 s-1 spongy and palisade tissue developed well, the number of stomata of RB450 treatment was significantly more than other treatments.The growth and photosynthetic characteristics of cherry tomato seedlings were investigated under seven light irradiations such as dysprosium lamps (white light; control, CK), red light emitting diodes (LEDs) (R), blue LEDs (B), yellow LEDs (Y), green LEDs (G), red and blue LEDs (RB) and red, blue and green LEDs (RBG) with the same photosynthetic photon flux density (about 300 μmol m-2s-1) for 30 days. Morphological appearances of seedlings were significantly different between respective irradiations of LEDs. Namely, the plants under RB and RBG were shorter and stronger than those under C, while those under Y, G and were weaker and higher. Photosynthetic pigments were shown to have significant difference under respective light irradiations of LEDs. The highest photosynthetic pigments were in leaves of seedlings with RBG, but the lowest pigments were in those with R and Y. Pn was the highest in leaves of seedlings with RB and RBG and the lowest in those with G. light compensation point and light saturation point of seedlings with R, RB and RBG were increased, but those with Y and G were decreased. Electronic transport rate, quantum yield of PSII and photochemical quenching in seedlings with RB and RBG were significantly greater than those the other LEDs. Compared with CK treatment, net photosynthesis of cherry tomato leaves was increased significantly under the light treatments of B, RB and RBG and reduced under R, Y and G. Chloroplasts of the leaves under the RB treatment were rich in grana and starch granules. Moreover, chloroplasts in leaves under RB seemed to be a distinct boundary between granathylakoid and stromathylakoid. Granathylakoid under treatment B developed normal, but the chloroplasts had few starch granules. Chloroplasts under RBG were similar to those under CK. Chloroplasts under R and G were relatively rich in starch granules. However, the distinction between granathylakoid and stromathylakoid under R and G was obscure. Chloroplasts under Y were dysplastic. Palisade tissue cells in leaves under RB were especially well-developed and spongy tissue cells under the same treatment were localized in an orderly fashion. However, palisade and spongy tissue cells in leaves under R, Y and G were dysplastic. Stomatal numbers per mm2 were significantly increased under B, RB and RBG.The growth and photosynthesis were investigated under dysprosium lamp (white light control, CK) and five LED light treatments designated as blue (B), blue & red (3:1, BR31), blue & red (3:2, BR32), blue & red (1:1, BR11), blue & red (1:3, BR13) with the same photosynthetic photon flux density (PPFD) (about 300 μmol m-2 s-1) for 30 days. The results showed that blue light dose had significant effects on plant morphogenesis, plant biomass, photosynthesis and chlorophyll content of cherry tomato. Specific leaf area (SLA) under respective light from large to small order was as follow:BR11> BR31> B> BR13> BR32> CK. Net photosynthesis (Pn) of the BR31 and BR11 treatment was significantly higher than that of other treatments, while Pn of the BR13 treatment was significantly lower than that of other treatments, the difference of stomatal conductance under respective light treatment was the same as that of Pn. Pn was positively correlated with thickness of leaves. Compared with CK, chloroplast development are all normal under light treatments. Chloroplast grana stacking layers was densely under BR31 and BR32, starch granules was less under BR32. Starch granules were significantly more under BR11 than that under the control. Grana stacking layers was thinner under B. Furthermore, compare with the control, anatomical structures had no significant difference under each treatment, but the thickness of the palisade tissue under BR11 was significantly less than other treatments. Leaf thickness under BR13 and BR11 was thicker. Moreover, the number of stoma was most under BR11. Pollen viability under BR13 and CK was significantly lower than those of other treatments. Moreover, the fruit weight and fruit number with irradiation of 60% blue light dose were significantly higher than those of other treatments, and content of lycopene, free amino acids, flavonoid and the ratio of sugar to acid were promoted with proportion of blue light increased in light source, while with proportion of red light increased, content of titratable acid in fruit was promoted. Furthermore, blue light accounted for 50%, content of soluble protein is the highest, and irradiation with the proportion of blue light accounted for 60%, content of sucrose, vitamin C was higher than other treatment. However, irradiation with light of the proportion of blue accounted for 25%, content of lycopene, soluble solids, soluble protein, soluble sugar, sucrose, free amino acids and anthocyanin in fruit were lower than other treatment.From the current result, we can conclude that the cherry tomato seedling developed dysplasia under different quality LED low light, and supplement yellow and purple light base on red and blue light can alleviate the stress of light, but can hardly reverse the these results. Cherry tomato seedling grew much better under different light quality high light (about 300μmol m-2 s-1) than under different light quality LED low light, but under monochromatic red, yellow and green light, plant growth and development were still limited. Compared with CK, plants growth and development were better under light containing blue light, and were best under the red and blue light. From physiological and economic point, light intensity setted 300μmol m-2 s-1 is benefit to cluture cherry tomatos in facilities. Blue light is indispenble component light for growth and development of cherry tomatoes, and dose of blue light in light source affected the growth and development of cherry tomatos. The plants grew better under 50%-75% dose of blue light, while 25% dose of blue light was not benefit to plant reproductive growth and fruit quality, and the larger proportion dose of blue light favor fruit quality. |
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