Effects Of Darkness And Light Recovery On Physiological Metabolism Of Petunia Hybrida Seedling

Seedling storage is one of the key components of high-quality industrial seedling. In China, seedlings are usually stored in total darkness. After darkness storage, seedling leaves usually become yellow and shedding, which are the typical signs of senescence. Petunia hybrida seedlings were used, darkness treatments were 0, 1, 4, 15d. Darkness and light recovery effects were studied.The results demonstrated that in darkness, Petunia hybrida plant root biological mass declined constantly. In light recovery, R/S decreased. Leaf soluble protein content, soluble sugar content, starch content decreased significantly, free amino acid content increased significantly. In darkness treatment, free amino acid possibly participated in plant osmoregulation, protein degradation and sugar content reduction were probably to maintain plant low level C, N metabolism under dark stress.In darkness, leaf MDA and H2O2 content increased constantly. POD, SOD and CAT activity increased then decreased. In light recovery, POD and CAT activity was relatively high, probably to eliminate MDA and H2O2 developed in darkness. 15d-dark-treated seedling leaf antioxidation system suffered certain injury.In darkness, leaf thickness, palisade tissue and sponge tissue thickness all decreased. 4d-dark-treated leave chloroplasts shape changed, stromal thylakoids disoriented. 15d-dark-treated leave chloroplasts appeared disorganized. When recovered under normal light condition, 4d-dark-treated seedling chloroplast structure could totally recover, while 15d-dark-treated seedling grana and lamella were vague.In darkness, leaf chlorophyll content decreased by 14.8%, 26.5%, 61.0%; Pn decreased by 18.4%, 31.6%, 56.6%. 4d-dark-treated seedling photosynthesis decline was mainly due to stoma limits while for 15d-dark-treated seedling, the decline was caused by non-stoma factors. Fv/Fm was 0.303 for 15d-dark-treated seedling, showed PSâ…¡reaction center was injuried.Once in light recovery, 4d-dark-treated seedling could recover to normal physiological condition within 8d, while 15d-dark-treated seedling slowly recovered and with low quality, in about 2 weeks, injury to plant under darkness could partially recover, however, it is not suggested to store seedling more than 2 weeks. Seedling root was more sensitive to darkness than shoot, antioxidant system response was not acute, 2 weeks darknss caused photosynthesis degration was due to non-stoma factors, and darkness effects could be reversed in light, all these conclusions provide academic support to flower seedling storage physiology research and storage techniques optimization.