Abstract: By controlling the soilwater content, 1-year-old potted cutting plants of Photinia frasery as the
materials, the effects of drought and flooding stress on the changes of malondialdehyde (MDA) content, the
membrane permeability, p igment content aswell as photosynthetic and physiological characters in summer and
autumn were studied. The results showed that MDA content, membrane permeability and anthocyanin (Ant)
content were distinctly increased, while the content of chlorophyll, the index values of net photosynthesis rate
( Pn) , water use efficiency (WUE) , apparent quantum yield (AQY) and carboxylation efficiency (CE) were
decreased. Meanwhile the available light intensity range was shortened with the declining of light saturation
point (LSP) and rising of light compensation point (LCP) under drought and flooding stress in summer and
autumn. On the other hand, the chlorophyll (Chl. ) content of control in summer was lower than that in au
tumn, but the values of Pn and CE in summerwere higher than these in autumn. In addition, the membrane
injury of Photinia frasery under drought and flooding stress in summerwasworse than autumn, the degradation
of Chl. in summerwas lower than autumn, the carotinoid (Car. ) content increased in summer and decreased
in autumn, the decrease of LSP and increase of LCP in summerwere lower than autumn, but the decrease of
Pn under drought stress in summer was lower than autumn, and the decrease of Pn under flooding stress in summerwas higher than autumn; moreover, flooding in summer had much more influence on membrane injury
and Pn, WUE, AQY, CE than drought stress, the decrease of Pn in initial stage was due to stomatal limita
tion, and then nonstomatal limitation dominated. The gray relational grade analysis showed that the relation
ship among climate factors and Pn ( from high to low) were temperature of atmosphere (Ta) , CO₂ concentra
tion and photon fluxdensity ( PFD). While drought in autumn had much more influence on membrane injury
and Pn, WUE, AQY, CE than flooding stress, the decrease of Pn wasmainly decided by nonstomatal limita
tion; The gray relational grade analysis showed that the retational factors to Pn ( from high to low) were Vapor
p ressure (Vp) , PFD, and then CO₂ concentration.

Key words: Photinia frasery, Water stress, Photosynthetic characteristics, Membrane injury