Response Of Seed Germination And Seedling Growth To Different Lights Of Plants From Different Environment

Sunlight is an important source of energy for life on earth.A large number of studies show that light is an important environmental factor affecting plant seed germination and Seedling Growth.Different photoperiod,luminous flux,light supplying time and spectral components will affect the seed germination,plant morphogenesis even plant life history.Due to the emissions of CFCs,the stratospheric ozone content decreased that result in UV-B radiation enhanced on the earth surface.At present,there are a lot of researches reported the effects of enhanced UV-B radiation on plant growth and metabolism from molecular to ecosystem levels.There also have a number of studies which investigated the effects of UV-B radiation together with other environmental factors on plants.Based on these researches,some studies showed that strong photosynthetic active radiation(PRA)or white light can decrease the enhanced UV-B damage to plants.Other studies also showed that the pattern of plants' response to enhanced UV-B radiation is related to the original environment conditions.As well as flavonoids,endogenous hormones are the important plant internal factors regulating seed germination and seedling growth in response to different environment conditions.We study on the response of plants(Linum perenne,Heteropappus altaicus,Lepidium apetalum and Elymus nutans)from Tibetan Plateau(Qaidam Basin in Qinghai province and HeZuo in South Gansu province)to different lights under the condition of same temperature and different light supplies,witch are the enhanced UV-B and its combination with red light(660nm)and blue violet(450nm).The germination rate and duration were detected.High performance liquid chromatography(HPLC)was used to detect the changes of endogenous hormones during germination and seedling stage,and spectro-photometric method was used to measure the flavonoid levels at the seedling stage.Our study aim is exploring whether it could exist the interaction between the single lights on plants' response to UV-B radiation under enhanced red or blue lights,and the effects of environmental heterogeneity on plant response to light stress.Results show:(1)UV-B radiation decrease seed germination rate and prolong germination time,red light can reduce the negative effects of UV-B radiation on seed germination to some extend;blue violet superposition has a certain gain to UV-B effects in lowering seed germination rate anddelaying seed germination time.(2)Change trends of endogenous hormones response to different light depend on species,geographical and different period of growth.Overall,UV-B significantly increases the anti-growth hormone(ABA)level.Red and UV-B light significantly reduce the growth hormone(IAA,GAs,CTK)levels,and the reduction of the anti-growth hormone is more significant in seedling than in germination stage.There is no uniform trend of the effect of blue violet and UV-B on these two kinds of hormones.(3)The contents of the two kinds of hormones in germinating period are higher than that in the seedling stage.(4)The response of flavonoids to different lights has a certain strategy not only intra-specific but also inter-specific,UV-B significantly increase the content of flavonoids,superposition of red light and blue violet treatments can significantly reduce the effect of UV-B radiation,almost reach to the level of the control group.(5)The species from HeZuo have higher germination rate,endogenous hormones and flavonoids levels than those of the species from Qaidam Basin.In conclusion,the mixture of enhanced red light,blue violet and the PAR can cause a alternation in the response of plants to UV-B radiation stress,enhanced red light with UV-B made plants have the same response level in germination and flavonoids as the control group,and the response of plants to enhanced blue violet depends on species,geographical and different period of growth.The response of flavonoids to environmental stress is more conservative than that of hormones.The species from Gansu HeZuo are more sensitive to different light qualities than those from Qinghai Qaidam.