[Effects of light intensity on material and energy metabolism of Viola yedoensis]

Light energy is an important factor affecting plant growth. The hypothesis of "light-cold and heat property" holds that the original plants of traditional Chinese medicines(TCM) with cold property can obtain more energy to maintain growth in high light intensity environment, whereas the original plants of TCM with heat property prefer weak light environment. The current experiment investigated the effects of different light intensities on primary metabolites levels, energy levels, cell apoptosis, and leaves ultrastructure of Viola yedoensis, the original plants of TCM Violae Herba with cold property. There were five treatment groups of V. yedoensis, which was planted under Li1(8 500 lx),Li2(7 250 lx),Li3(6 000 lx),Li4(4 750 lx),Li5(3 500 lx)LEDs light intensity conditions, respectively. After harvest, primary metabolites levels, contents of ATP, ADP, AMP, activities of ATP synthesis and hydrolysis related enzyme, as well as cell apoptosis activation degree were measured, and transmission electron microscopy technique was used to observe leaves ultrastructure. The results showed that the total sugar, total protein, contents of ATP, ADP and AMP, activities of NADH dehydrogenase, cytochrome C reductase, ATP synthase and ATP hydrolase were positively correlated with light intensities(P<0.05). The crude fat content, activities of SDH and CCO enzyme showed a trend of increasing first and then decreasing, the highest value were found in Li2 group and Li3 group respectively(P<0.05). The vitality of caspase-3 and caspase-9 was negatively correlated with light intensities(P<0.05). The structure of chloroplast and mitochondria were normal and intact in Li1-Li3 groups, and the damage degree of Li4 and Li5 groups increased with the decrease of light intensities. The analysis of results indicated that the structure of chloroplast and mitochondria of V. yedoensis is normal under the light intensity of 6 000-8 500 lx, which can obtain more energy to maintain its growth and metabolism. When the light intensity is lower than 4 750 lx, the chloroplast morphology and mitochondrial membrane are damaged, affecting the metabolism of material and energy. There was no significant difference in energy charge of V. yedoensis in the light intensity range of 3 500～8 500 lx. The effect of light intensity on energy metabolism of V. yedoensis accords with the hypothesis of "light-cold and heat property".