Effect Of Temperature Stress On Photosynthesis In Strawberry Leaves

Potted plants of five strawberry varieties differing in temperature resistivity(FengXiang(not cold-resistant), MingLei(cold-resistant), AiMei(not heat-resistant),ShuoLu(heat-resistant) and GuiNuGan(cold&heat resistant))were subjected to 25±1℃(control) , FengXiang, MingLei, GuiNuGan: 10±2℃,0±2℃(low temperature stress),AiMei,ShuoLu,GuiNuGan: 30±2℃,38±2℃(high temperature stress), 800~1000μmol·m-2·s-1 PFD and 10 hours photoperiod during 7 days and recovered during 7 days at25±1℃ at the same light regime. The effects of temperature stress on the operation ofphotosynthetic apparatus and the protective mechanism in leaves of strawberry plantwere studied. Compared with control, net photosynthetic rate (Pn), apparent photosyntheticquantum yield (AQY), carboxylation efficiency (CE), photochemical efficiency (Fv/Fm),photochemical quenching (qP) and quantum yield of PSII photochemistry (ΦPSII) alldeclined under temperature stress. On the other hand, photorespiratory rate(Pr)and no-photochemical quenching (qN ) increased under temperature stress. Compared the five strawberry varieties, we found that under low temperature stress,the injury to cold-resistant variety was lower than that in not cold-resistant variety, andthe injury to heat-resistant variety was lower than that in not heat-resistant variety underhigh temperature stress.Photorespiration and xanthophyll cycle were the major protectivemechanism under temperature stress in strawberry leaves. The effects of high light stress(1800 μmol·m-2·s-1) under 5℃ and 38℃ to D1protein turnover were studied by Western-blotting in strawberry leaves. The resultindicates, after a week treatment with high light(4 hours a day),the degradation of D1protein under 38℃ was more than 5℃. Low temperature stress induced an inhibition ofD1 protein synthesis and . degradation. the degradation of D1 protein was acceleratedunder combined stress of heat and high light.