Effects Of Low Temperature And Poor Light On Seedlings Growth And Physiological And Biochemical Properties Of Pumpkin Seedlings (Cucubita Pepo L.)

For vegetables upgrowth,temperature and light are the absolutely necessarily factors. Temperature and light also are the mostly factors which restrict plant distributing in physical geography. While growing and developing, plant need some many accumulated tempertature and light. Low temperature and poor light are harmful to vegetables upgrowth. It is very cold in winter in west-China, furthermore, low temperature and poor light often occur there. All the bad weather can threaten vegetables planting in greenhouse.Pumpkin planting is a developing style as farming in greenhouse for these few years, which gives a strong function to adjusting planting structure and nursing rural economy in west district of China.One pumpkin cultivar that was selected as material in this paper was exposed to different low temperature-light regimes to investigate the responses of seedling growth and physiological and biochemical properties. The results were as followings:1. Height, stem diameter, the area of total leaves, fresh and dry weights of the above and under ground parts accumulation of pumpkin seedlings increased slowly and root-top ratio (R/T) decreased as the stress degree increased or the time prolonged above 15℃/5℃temperature any poor light conditions. However, the inhibitions of 15℃/5℃,poor lights are significantly different, Fresh and dry weight of root and root - top ratio (R/T) increased ,but height, stem diameter, the area of total leaves decreased.2. The root activities of Pumpkin seedlings increased slowly ,the contents of proline increased and the content of soluble protein decreased as the stress degree increased or the time prolonged above 15℃/5℃temperature and any poor light condition. However, the root activities decreased and the contents of proline increased at first and then decreased under 15℃/5℃temperature and any poor lights.3. Membrane permeability,POD activity and content of MDA increased, while SOD and CAT activities of pumpkin seedlings decreased in leaves as the stress degree increased or the time prolonged. The results suggested that the membrane permeability, MDA content and activities of SOD, CAT, and POD can be used as indicators for identifying cultivars tolerance to low temperature and light stress.4. The contents of chlorophyll increased at first and then decreased under any temperature and poor light.The net photosynthetic rate (Pn) ,evaporation rate...