旺长期烤烟叶片的叶绿素荧光特性与激发能分配

以烤烟品种龙江911为试验材料,研究了烤烟植株上、中、下3个部位叶片实际光化学效率(ΦPSⅡ)和PSⅡ最大光能转化效率(Fv/Fm)的日变化,以及激发能的分配特性。结果表明,烤烟叶片Fv/Fm和实际光化学效率(ΦPSⅡ)中午降低,PSⅡ功能下调,有明显的光抑制。在光合有效辐射(PPFD)逐渐增强过程中,Fv/Fm和ΦPSⅡ降低,非光化学猝灭(NPQ)增加,激发能由PSⅠ向PSⅡ分配的比例增加,说明引起烤烟光抑制的原因除了NPQ之外,分配给PSⅡ能量增加是光抑制非常重要的因素。PPFD逐渐减小时,光抑制逐渐减缓,光化学效率恢复,激发能分配不平衡性系数(β/α-1)下降,PSⅡ能量负荷减轻,失活的PSⅡ恢复活性。

CHARACTERISTICS OF CHLOROPHYLL FLUORESCENCE AND EXCITED ENERGY DISTRIBUTION IN LEAVES OF TOBACCO AT FAST GROWING STAGE

A study was conducted, using chlorophyll fluorescence technique and tobacco variety Longjiang 911 as material, to investigate the diurnal changes of PSⅡ and maximum quantum efficiency of photosystem II photochemistry (Fv/Fm) and excited energy distribution in upper, middle and bottom stalk leaves of tobacco, respectively. The results showed that the decreasing of Fv/Fm and actual photochemical efficiency of PSⅡ(ΦPSⅡ) with obvious midday-depression, and down-regulation of the functional photosystem Ⅱ reaction centers result in significant photoinhibition. With the increasing of photosynthetic actual irradiation (PAR),Fv/Fm and ΦPSⅡ gradual declined, nonphotochemical quenching (NPQ) and the fraction of excited energy allocated to PSⅡ increased. These results indicated that photoinhibition in tobacco leaves were caused primarily by increasing of excited energy allocated to PSⅡ to enhance reversible inactivation of PSⅡcenters other than NPQ. With the decreasing of PAR, Fv/Fm and ΦPSⅡ increased, and NPQ and unbalance index of excited energy allocated to PSⅡ and PSⅠ (β/α-1) declined respectively.It was indicated that the recovery of PSⅡ photochemical efficiency was caused primarily by renewing PSⅡ activation due to unloading the energy burden of PSⅡ.