Effect On Enhancing Anti-chilling And Low Light Stress Of ALA And CaCl₂on Pepper Seedlings

Even though China now boast the largest area of horticulture facilities in the world, most of them are simple type with very low level of environmental controlling. The capability of increasing and keeping the temperature in the greenhouse is very weak, so much that chilling are very frequent in the cold season. The photo permeability rate of the greenhouse and plastic shed can only get to50%. To make things worse, the rainy weather in southwest China further lowers the photo permeability. Chilling and low light always happen together, which cause very serious consequences such as wilting, etiolation, freezing, dieing, root-rotting in the seedling period and flower dropping, fruit dropping, fruit withering in the flowering and fruit-bearing period. The measure against chilling and weak light include adopting new-type plastic film, clearing the film timely, opening and cover the grass curtain at regular time, installing light-reflecting aluminizing film or illuminating equipments to increase light intensity etc.. These measures are either troublesome or costly. By contrast, application of chemicals against chilling and lowlight, if possible, can be much convenient and time and labor-saving.In this study, two varieties of pepper seedlings in four-leaved stage were sprayed with solutions of CaCl2、ALA of different concentrations, and treated with chilling and low light simultaneously. The soluable sugar, chlorophyll the chilling-induce-wilting index were tested. The results showed that1mmol/L of CaCl2and30mg/L of ALA were suitable for Yujiao No5, and2mmol/L of CaCl2and45mg/L of ALA were suitable for Xinxiang No8. Further experiment showed the resistant function of the2chemicals to single chilling and single low light are different. CaCl2mainly functions at the single chilling while ALA mainly contributes to photosynthesis under low light. Combining tests of these2chemicals showed, conbination treatment had the most effective result.Chilling and low light damage plant in many ways, first, it damages the cellular membrane system and increases the leakage rate of electrolyte; second, it destroys antioxidant enzymes system, which cause the lipid peroxidation and accumulation of activate oxygen; third, it affects the level of osmotic regulator; last, low light can cause decrease of chlorophyll content in plant and the ratio of chlorophyll a/b. This study demonstrated that ALA and CaCl2in appropriate concentration can alleviate the electrolyte leakage of the pepper seedlings under chilling and low light, and keep the stability of the membrane system.Chilling can lower the activity of SOD and accumulate MDA.This study shows that application of ALA and CaCl2in appropriate concentration also can keep the activity of SOD high in pepper seedlings under chilling and low light and keep low level of MDA simultaneously. Activity of SOD and MDA content are of significantly negative correlation.Proline and soluable sugar, as two major osmotic regulators, play very important roles in anti-chilling in plants.This study shows that application of ALA and CaCl2can help keep high level of praline and soluable sugar in the leaf.Besides, application of the above substances can help keep the level of total chlorophyll high and decrease the ratio of chlorophyll a/b, which exert a very critical function in improving the light-harvesting capability of LHP1and enhancing the electron-transmitting efficiency of electron-transmitting chain.And it further increases the photosynthesis of plants under stress conditions.