珙桐苗木叶片光合特性对土壤干旱胁迫的响应

Photosynthetic Characteristics of Davidia involucrata Baill.Seedlings under Soil 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.

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,but 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 that of control（P0.05）.The chlorophyll florescence parameters Fv/Fm,Yield,ETR,and qP decreased sharply（P0.05） under drought stress.The results proved that drought stress restrained photosynthetic and growth of D.involucrata,which was very sensitive to drought stress.