EFFECTS OF WATERLOGGING ON THE GAS EXCHANGE, CHLOROPHYLL FLUORESCENCE AND WATER POTENTIAL OF QUERCUS VARIABILISAND PTEROCARYA STENOPTERA

Abstract

(2 , 100049) (Quercus variabilis) (Pterocarya stenoptera) 。 70 d 100%。 (Pmax)、(Gs)、(Fv/ Fm)。 7 d , 39%, 42%; 38. 8%, 71. 9%; 5 d , 0. 694 0. 757。 , 、 , 。 70 d 94. 1 %, 0. 537。 , , 。 ; 33 d , Abstract Background and Aims Cork oak (Quercus variabilis)and China wingnut (Pterocarya stenopter-a)are important species in the subtropical riparian and drawdown areas of reservoirs and ponds in China. Methods We investigated the effect of waterlogging on morphological and physiological characteristics of these species. We measured the maximum net photosynthesis rate (Pmax), stomatal conductance (Gs), Chla fluo-rescence maximum quantum efficiency (Fv/ Fm), chlorophyll content and water potential on different days during a period of waterlogging. Key Results Throughout a 70_day waterlogged period , the survival rates of seedlings of the two species were 100 %. The earliest effects of waterlogging were significantly decreased Pmax , Gs and Fv/ Fm. On the 5th day of waterlogging , Fv/ Fm of cork oak and China wingnut decreased to 0. 694 and 0. 757 , respectively. On the 7th day , significant reduction of Pmax(cork oak , 39 % of control ; China wingnut , 42 %)and Gs(cork oak , 38. 8 % of control ;China wingnut , 71. 9 %)were observed. With prolonged waterlogging , Pmax , Gs and Fv/ Fm recovered gradually to control values in China wingnut , but not in cork oak where values decreased continuously. On the 70th day , Pmax of cork oak was reduced by 94. 1 % of control and Fv/ Fm was only 0. 537. Waterlogged China wingnut seedlings developed hypertrophied lenticels and adventitious roots at their stem base and exhibited no visible symptoms of injury (neither mortality , leaf chlorosis , leaf necrosis , leaf ab-scission nor reduced chlorophyll content). However , cork oak showed leaf necrosis with waterlogging .The