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不同快、慢生长型的杨树无性系幼苗,在不同渗透势溶液(PBG 6000)中经受12h、24h的轻度、中度和严重胁迫,净光合速率(P_n)均明显降低。在轻度胁迫下,快生长型杨树品种比慢生长型下降迅速;中度和严重胁迫的品种,却表现出受抗旱性强弱的差异。解除干旱处理后,P_n恢复不一。经过中度和严重胁迫的品种均难于恢复,轻度胁迫过的达正常水平。在恢复过程中,杨树各品种的P_n回升趋于稳定。与对照的P_n相比,快慢类型,表现出波动周期与其振幅(P_n回升的大小)的特征,前者P_n(如群众44)恢复周期短、振幅大、恢复快,而后者(如小叶杨)则相反。这种P_n变化趋势在抗旱强速生和抗旱差慢生的品种上表现明显,对选育抗旱速生的品种鉴定有着重要的意义。
Different fast and slow-growing poplar clones had mild, moderate and severe stresses at 12 h and 24 h in different osmotic potential solutions (PBG 6000), and their net photosynthetic rate (P_n) decreased significantly. Under mild stress, the fast-growing poplar varieties descended more rapidly than the slow-growth ones; moderately and severely stressed ones showed differences in drought resistance. After the lifting of drought treatment, P_n recovered. After moderate and severe stress species are difficult to recover, mild stress up to the normal level. In the recovery process, the poplar varieties P_n rebound stabilized. Compared with the control P_n, the fast and slow types show the characteristics of fluctuating cycle and its amplitude (the magnitude of P_n rebound). The former P_n (such as the mass 44) has a short recovery period, a large amplitude and rapid recovery, while the latter in contrast. The trend of P_n is obvious in varieties with slow drought-resistance and drought-resistance, which is of great significance to the identification of varieties of fast-growing breeding drought-resistance.