干旱胁迫对两种油桐幼苗生长、气体交换及叶绿素荧光参数的影响

Influence of drought stress on the growth,leaf gas exchange,and chlorophyll fluorescence in two varieties of tung tree seedlings

为了探究干旱胁迫对两种油桐(三年桐和千年桐)幼苗光合生理特性的变化及响应,采用盆栽试验,研究不同水分处理(正常供水、轻度干旱、中度干旱、重度干旱)对油桐幼苗生长、叶片气体交换及叶绿素荧光参数的影响。结果表明:与对照相比,轻度干旱胁迫对两种油桐生长、气体交换及叶绿素荧光参数无明显影响(P>0.05);中度干旱及重度干旱使两种油桐的叶绿素SPAD值、生长量、净光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)、气孔限制值(L_s)、最大净光合速率(P_(nmax))、光饱和点(LSP)、表观量子效率(AQY)、暗呼吸速率(R_d)、最大光化学效率(F_v/F_m)、实际光化学量子效率(Φ_(PSⅡ))、电子传递速率(ETR)及光化学猝灭系数(q_P)显著下降(P<0.05),且在重度干旱胁迫下迅速下降,胞间CO_2浓度(C_i)、水分利用效率(WUE)、光补偿点(LCP)、初始荧光(F_o)、非光化学猝灭系数(NPQ)显著升高(P<0.05);中度干旱胁迫下油桐幼苗P_n的降低是由气孔因素及光合机构活性降低的非气孔因素共同引起的,而重度干旱胁迫下光合作用的下降主要是由光合机构活性降低的非气孔因素引起的。三年桐的光合机构活性及光合效率高于千年桐,对干旱胁迫的适应性较千年桐强。

This study investigated the effects of drought stress on seedling growth and leaf photosynthetic physiological characteristics in two species of tung tree （Vernicia fordii and Vernicia montana）. A pot experiment was conducted to study the effects of different water treatments （normal irrigation, light drought, moderate drought, and severe drought） on the growth, leaf gas exchange, and chlorophyll fluorescence of two kinds of tung tree seedlings. The results showed that light drought stress did not have any significant effect （P〉0.05） on growth, leaf gas exchange, and chlorophyll fluorescence of the seedlings compared to that under normal irrigation. Modest drought stress significantly decreased （P〈0.05） tung tree seedlings＇ chlorophyll SPAD value, growth, net photosynthetic rate （Pn）, stomatal conductance （Gs）, transpiration rate （Tr）, stomatal limitation value （Ls）, maximum net photosynthetic rate （Pnmax）, light saturation point （LSP）, apparent quantum yield （AQY）, dark respiration rate （Rd）, maximum photochemical efficiency （Fv/Fm）, actual photochemical quantum efficiency （ΦPSⅡ）, electron transport rate （ETR）, and photochemical quenching coefficient （qP）. Severe drought stress increased intercellular CO2 concentration （Ci）, water use efficiency （WUE）, light compensation point （LCP）, initial fluorescence （Fo）, and non-photochemical quenching coefficient （NPQ） of the seedlings. Under modest drought stress, the decrease in net photosynthetic rate was primarily caused by stomatal and non-stomatal factors of the tung tree seedlings, while the decrease in net photosynthetic rate under severe drought stress was probably due to non-stomatal factors. Our results suggest that Vernicia fordii has a higher photosynthetic activity and efficiency, and a stronger adaptability to drought stress than Vernicia montana.