两种相思叶片光合作用对干旱的反应

RESPONSE OF PHOTOSYNTHESIS IN LEAVES OF ACACIA SPECIES ON WATER STRESS

比较了绢毛相思和大叶相思的叶特性,旱季的田间光合速率和供水短缺对光合速率、气孔传导率和蒸腾速率的影响。绢毛相思的比叶重、单位叶面积的叶绿素含量和叶绿素a/b均较大叶相思高,但叶片含水量略低。绢毛相思的中午时叶片水势为-0.6±0.05MPa,而大叶相思则为-1.18±0.07MPa。绢毛相思叶片水势降低时,叶片鲜重的变化较大叶相思大。旱季10月,两种相思的日平均光合速率相近似,但绢毛相思有较高的气孔传导率和蒸腾速率。干旱处理引起大叶相思叶片水势降低较绢毛相思大。当绢毛相思叶片水势从-0.76MPa降至-1.35MPa,日平均光合速率降低49.4％;而大叶相思,叶片水势从-1.22MPa降低至-2.2MPa,日平均光合速率降低55.0%。大叶相思叶片水势降低的幅度比较大,光合速率降低亦大。

Leaf characteristic, net photosynthesis which was measured in the field and green house, the effects of water stress on photosynthetic rate, stomatal conductance and transpiration in leaves of Acacia auriculaeformis and Acacia cincinata were studied. The ratio between weight and area in leaf, chlorophyll content and chlorophyll a/b in Acacia cincinata were greater than that of Acacia auriculaeformis. But higher water content in leaves was found in Acacia auriculaeformis. Leaf water potential at noon was-0.6±0.05MPa for Acacia cincinata and by-11.8±0.07 MPa for Acacia auriculaeformis in same condition. The change of leaf fresh weight for Acacia auriculaeformis was greater than that of Acacia cincinata during leaf water potential fall down.A same rate of photosyhnthesis which was measured in the field was found for these species. But apparently higher stomatal conductance and transpiration were observed in leaves of Acacia cincinata. It may be beneficial for CO2 assimilation for this species in the field during dry season of a year. The greater fall of leaf water potential in Acacia auriculaeformis was found during water stress developed as comparied with that of Acacia cincinata. And diurnal average rate of photosynthesis decreased by 49.4% as leaf water potential fall from -0.75 MPa to -1.35 MPa in leaves of Acacia cincinata whereas a fall by 55.0% in leaves of Acacia auriculaeformis as leaf water potential declined from -1.22 MPa to -2.2 MPa.