The Effects Of Low Temperature And Poor Light On The Growth Physiological Characteristics Of Photosynthesis In Pepper Seedlings(Capsicum Annuum L.)

Pepper seedlings(Capsicum annuum L.)of two cultivars Sensitive significantly to cold was selected as material in this study to research the effects of the combination of poor light and lower temperature, poor light and critical temperature stress on growth index, Chlorophyll content , chlorophyll fluorescence parameter, photosynthetic characteristics and resistant-oxidation enzyme activities in leaves of peeper seedlings.The results showed as follow : Leaf plastochron index(PI) and height of pepper increased a litter under the combination of poor light and lower temperature, however which decreased obviously under the combination of poor light and critical temperature. At the same time, stem diameter, fresh weight of root and top, dry weight of root and top, dry weight to fresh weight of root and top of both pepper cultivars all decreased under the combination of poor light and low temperature. the combination of poor light and lower temperature made root to top ratio of two pepper cultivars decreased . the combination of poor light and critical temperature had a complex influence on root to top ratio of two pepper cultivars. root to top ratio of Qicunhong almost equal to that of control , but which of Longjiao NO.2 increased. In all, the combination of poor light and lower temperature had top growing well, however the combination of poor light and critical temperature had root growing well. Net photosynthetic rate and stomatal limitation value decreased, however intercellular CO2 concentration decreased. The cause of reduction of net photosynthetic rate in pepper seedlings under low temperature and poor light stress might be mainly non-stomata limitation .Chla content, Chlb content ,Chl(a+b) content and Chl(a/b) all reduced after treatment for 10 days . Fv/Fm, ?PS â…¡, qP and Fv '/Fm' decreased with degree increasing and time prolonging of low temperature and poor light.At the same time , Prate decreased ,but Drate and Ex increased under low temperature and poor light. Drate was the main way of superfluous light allocation .In all ,the change of the above parameters were smaller under lower temperatur(e19℃/12℃)than critical temperatur(e15℃/8℃),but poor light had different influence on different low temperature plot . Under the combination of poor light and both lower temperature, critical temperature, light compensation point(LCP), light saturation point(LSP), apparent quantum yield(AQY), CO₂ saturation point(CSP), carboxylation efficiency(CE) and temperature compensation point(TCP)decreased , but CO2 compensation point(CCP) increased. At the same time , the start time of photosynthesis(STP) prolonged. The ability and efficient of light and CO2 ,TCP of pepper seedlings under poor light and lower temperature were higher than that of pepper seedlings under poor light and critical temperature, but STP of pepper seedlings was shorter under poor light and lower temperature. POD activity ,contents of MDA and membrane permeability increased , but SOD and CAT activities decreased in leaves of pepper seedlings with degree increasing and time prolonging of low temperature and poor light. The effects of critical temperature(15℃/8℃)on resistant-oxidation enzyme activities and membrane permeability in leaves of pepper seedlings was more significant than that of lower temperature (19℃/12℃). Poor light 90μmol?m-2?s-1 made POD activity more increased, while contents of MDA and membrane permeability less increased , and SOD and CAT activities less decreased in leaves of pepper seedlings under lower temperature (19℃/12℃), while which had opposite effect under critical temperature(15℃/8℃). Pepper Longjiao NO.2 was more tolerant to low temperature and poor light than pepper Qicunhong . In all , the ability of tolerance to low temperature and poor light in pepper Longjiao NO.2 was stronger than that in pepper Qicunhong .