<正>盐胁迫明显抑制杨树幼苗高生长，其高生长速率随胁迫时间的延长和盐浓度的增加而减小，与此同时，叶片中Ｃｌ￣－、Ｎａ￣＋的累积则增加，叶片中游离脯氨酸的累积在胁迫后约２～３ｄ达到峰值，Ｋ￣＋累积则在胁迫后约２周迅速增加，两者都是在峰值之后随胁迫时间的延长而下降。杨树幼苗对Ｃｉ￣－和Ｎａ￣＋的吸收并不同步，胁迫后期Ｎａ￣＋／Ｃｌ￣－的值逐渐升高，在浓度为０．３％的处理组比值可达１．５．同时，Ｎａ￣＋／Ｋ￣＋值的升高是Ｎａ￣＋吸收增加而Ｋ￣＋吸收减少的结果。外源Ｋ￣＋、Ｃａ￣２＋对盐胁迫抑制高生长有一定的缓解作用，但Ｋ＋的作用不及Ｃａ２＋。

Salt-stress inhibits the height growth of poplar seedlings significantly, and the rate of height growth decreases with the lasting of salt-stress and increase in salinity from 0. 1 % to 0. 3%. Meanwhile, the accumulation of Cl~- and Na~+ in leaves increases. Free proline accumulation in leaves culminates after 2～ 3 days of salt stress, K~+ accumulation increases rapidly after about 2 weeks of Salt stress, both of which decrease after the culmination with the extension of salt stress. The absorption by poplar seedlings of Cl~- and Na~+ doesn’t take place simultaneously. In later sarge of salt stress the value of Na~+ /Cl~- rises gradually. Under 0. 3% level of salinity, this value may reach 1. 5, and the rise of Na~+/K~+ value results from the increase of Na~+ absorption and the decrease of K~+. External K~+ and Ca~2+ can reduce the inhibition of salt stress to height growth to a certain degree, but the effect of K~+ is not as good as that of Ca~2+.