珙桐苗木叶片光合特性对土壤干旱胁迫的响应

摘要

With control soil water content, the effects of soil drought stress on leaf area, chlorophyll content,photosynthetic and chlorophyll florescence parameters of two-year-old Davidia involucrata seedlings were measured. The purpose was to investigate the response of photo-system of D. involucrata to soil drought stress. The result showed that drought made the seedlings lost water quickly and leaves fell off soon,leaf area reduced sharply. Each treatment were significantly lower 23 ％ to 98％ than that of control,out the chlorophyll content in unite area had no significantly change. Moreover,photo-system suffered a serious damage under drought stress. The net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), water use efficiency (WUE) and stomata limitation (Ls) were significantly lower than hat of control (P＜0. 05). The chlorophyll florescence parameters Fy/Fm, Yield,ETR, and qp decreased sharply (P＜0.05) under drought stress. The results proved that drought stress restrained photosynthetic and growth of D. involucrata, which was very sensitive to drought stress.%通过控制土壤含水量,研究了土壤干旱胁迫对2年生珙桐(Davidia involucrata Baill.)幼苗叶面积、叶绿素含量、光合作用及叶绿素荧光参数的影响,以探讨珙桐光合作用对土壤干旱胁迫的响应机理.结果表明,干旱胁迫后,珙桐叶片失水脱落,各干旱胁迫处理叶面积比对照显著降低23%～98%,但单位面积的叶绿素含量却无显著变化;干旱处理的珙桐幼苗净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、水分利用效率(WUE)显著低于对照(P<0.05);干旱胁迫对珙桐幼苗叶片的初始荧光产量(F0)及最大荧光产量(Fm)没有产生显著影响,却显著降低了PSⅡ最大光化学量子产量 (Fv/Fm)、PSⅡ实际光化学量子产量(Yield)、电子传递速率(ETR)及光化学淬灭系数(qP),使非光化学淬灭系数(qN)显著升高(P<0.05).研究发现,土壤水分亏缺对珙桐叶片的光合系统造成了不可逆的伤害,严重抑制了其正常的光合作用和生长发育;珙桐幼苗对土壤干旱胁迫极为敏感.