光胁迫下烤烟幼苗叶片光抑制及Ca^(2+)的缓解作用

Photoinhibition in Leaves of Flue-cured Tobacco Seedlings under Light Stress and Its Alleviation by Ca^(2+)

利用FMS-2型调制式脉冲荧光仪测定烤烟品种‘龙江911’叶片的叶绿素a荧光日变化。分别为烤烟幼苗由温室弱光下移植到室外强光下(光胁迫)、喷施Ca2+的烤烟幼苗由温室弱光下搬到室外强光(Ca2+处理)和温室内的烤烟幼苗(对照)3个处理。结果表明:光胁迫下的烤烟幼苗叶片原初光化学效率(Fv/Fm)的日变化为双峰曲线,峰值分别出现在08:00和15:00左右,初始荧光(F0)上升。光胁迫下的叶片光化学猝灭系数(qP)、实际光化学效率(ΦPSⅡ)和电子传递速率(ETR)同Fv/Fm一样降低,但达到低谷以后恢复到原来的水平,说明烤烟幼苗突然暴露在强光下发生了严重的光合作用的光抑制。同光胁迫下的烤烟幼苗比较,Ca2+处理的叶片Fv/Fm下降的幅度较小,说明Ca2+对光胁迫下烤烟幼苗的光抑制起到了缓解作用。

The diurnal variation of chlorophyll fluorescence in leaves of flue-cured tobacco, the variety‘Longjiang 911’, was investigated by using a portable fluorometer （FMS-2, Hansatech, UK）. Three treatments are designed, namely, flue-cured tobacco seedlings grown in greenhouse under low light suddenly exposed to high light out-greenhouse, flue-cured tobacco seedlings grown in greenhouse under low light treated with Ca^2＋ （ 10 μmol· L^-1 ） exposed to high light out-greenhouse, and seedlings grown in greenhouse under low light （CK）. Results showed that the diurnal variation of the maximal yield of PSⅡ photochemistry in dark-adapted leaves （FJF） under light stress was a double-peak curve, and the peak values were at 8：00 and 15：00, respectively. Minimal fluorescence with all PSII reaction centers open （F0 ） increased. Photochemical quenching （qp）, quantum efficiency of photosystemⅡ （ ΦPSⅡ） and electron transport rate of photosystemⅡ（ ETa ） in leaves under light stress declined, and then restored to its original level after high light at noon. It suggests that the serious photoinhibition occurs when leaves of flue-cttred tobacco seedlings are suddenly exposed to high light. The F/F in leaves treated with Ca^2＋ decline with a smaller range than those under light stress, so Ca^2＋ can alleviate photoinhibifion in leaves of flue-cured tobacco seedlings.