水分和热胁迫处理对4种针叶树苗木气体交换和水分利用效率的影响

Effects of Water Plus Heat Stress on Gas Exchange and Water Use Efficiency in Four Species of Coniferous Seedlings

以杉木、马尾松、花旗松和北美乔柏为研究对象 ,研究了水分和热胁迫对生长期间苗木的气体交换、瞬间水分利用效率和稳定碳同位素组成 (δ1 3C值 )等生理生态指标的影响 ,结果如下 :(1 )水分胁迫使杉木、马尾松、花旗松和北美乔柏 4个树种的净光合速率显著下降。但热胁迫只影响杉木和北美乔柏的净光合速率 ,对马尾松的净光合速率影响不大。 (2 )对针叶气孔导度的研究发现 ,水分和热胁迫均对马尾松苗木针叶气孔导度有显著影响 ,但对杉木和北美乔柏苗木针叶的气孔导度只有轻微影响。 (3)水分和热胁迫处理对马尾松苗木的瞬间水分利用效率有显著影响 ,但对杉木和北美乔柏的瞬间水分利用效率无显著影响。 (4 )水分胁迫处理对杉木、马尾松、花旗松和北美乔柏 4个树种的稳定碳同位素组成 (δ1 3C值 )均有显著影响 ,随着水分胁迫程度的加深 ,4个树种苗木针叶的δ1 3C值增大 (负值绝对值变小 ) ,说明其永久水分利用效率更高。 (5 )热胁迫对杉木和北美乔柏苗木针叶的δ1 3C值有显著影响 ,且在热胁迫下 ,两树种苗木针叶的δ1 3C值减小 (负值绝对值增大 ) ,即永久水分利用效率下降。但热胁迫对马尾松和花旗松苗木的δ1

Effects of water plus heat stress on gas exchange and carbon isotope composition of Cunninghamia lanceolata,Pinus massoniana,Pseudotsuga menziesii and Thuja plicata seedlings were measured during a three\|cycle stress period in spring 2001 at the University of British Columbia. The results were shown as follows:After 36 days water stress treatments, the net photosynthetic rate of four species decreased significantly. But heat stress only affected the net photosynthetic rate of C.lanceolata and T.plicata . It was only observed that the needle conductance to water vapor of P.massoniana was significantly affected by both water and heat stress. The needle conductance to water vapor of other species had just a slight change after water and heat stress treatment. Therefore, instantaneous water use efficiency, which was expressed as the ratio of net photosynthetic rate( P n, μmol·m -2 s -1 ) to stomatal conductance to water vapor ( g wv , mmol·m -2 s -1 ), had no significant difference except for P.massoniana .There were significant differences in carbon isotope composition (δ 13 C) among four species under water stress treatments. Along with prolong of water stress, the δ 13 C value of all four species increased. This meant that the water use efficiency ( WUE ) would be improved under water stress. Heat stress treatment had also significant effects on δ 13 C of C.lanceolata and T.plicata . But the differences of δ 13 C were not observed under heat stress in P.massoniana and P.menziesii .