遮光对松属3个树种幼树光合特性和荧光参数的影响

通过搭建遮光棚模拟空旷地(不遮光对照)、林隙(46%遮光)、林下(81%遮光)等3种光照环境,研究了黑松Pinus thunbergii,油松Pinus tabuliformis,赤松Pinus densiflora等幼树叶片光合特性和叶绿素荧光动力学特征随梯度光照强度的变化规律,以期了解3个树种对不同光环境的适应性对策,为华北地区人工林的天然更新及长期经营提供理论依据。结果表明:随着光照强度的降低,黑松幼树净光合速率(P_n),蒸腾速率(T_r),水分利用效率(E_WUE),性能指数(I_abs),质体醌库的面积(S_m),PSⅡ捕获的能量从Q_A传递到Q_B的效率(Ψ_O),PSⅡ捕获的能量从Q_B传递到PSⅠ的效率(Ψ_RE),单位反应中心吸收(ABS/RC)、捕获(TRo/RC)、用于电子传递(ETo/RC)的能量均减小。油松幼树净光合速率(P_n),水分利用效率(E_WUE),性能指数(I_abs),PSⅡ捕获的能量从QA传递到QB的效率(Ψ_O),PSⅡ捕获的能量从QB传递到PSⅠ的效率(Ψ_RE),单位反应中心吸收(ABS/RC)、捕获(TRo/RC)、用于电子传递(ETo/RC)的能量在46%遮光条件下达到最大值。赤松幼树光合特征参数及叶绿素荧光参数在不同遮光条件下差异不显著(P>0.05)。因此,赤松对弱光的利用能力最强,能够适应不同的光照环境;黑松在光照充足的环境中生长状况较好;油松适宜在轻度遮光的林隙环境中生长。

Photosynthetic characteristics and chlorophyll fluorescence of three Pinus tree species with shading

Seedling stage is the most sensitive and vulnerable period of the individual life cycle on the environment. The update, survival and growth of young trees influenced larger by the change of light radiation. This paper focused the study on the change rule of young tree leaf photosynthetic characteristics and chlorophyll fluorescence kinetics characteristics along with the change of light intensity, which were three species, Pinus thunbergii, Pinus tabuliformi, Pinus densiflora. The goal was to investigate the three species' adaptive strategy to different light environments through building shading to mimic the open place, gap, understory(i.e. 0%, 46% and 81% sun-shading) and provide theoretical for natural regeneration and long-term management of plantations in north China. Variables including P_n (net photosynthetic rate), T_r (transpiration rate), E_WUE (water use efficiency), I_abs (performance index on absorption basis), S_m (normalized total complementary area above the O-J-I-P transit), Ψ_O (probability that a trapped exciton moves an electron into the electron transport chain beyond QA-(electron transfer mediators)), Ψ_RE (probability that a trapped exciton moves an electron into the electron transport chain beyond Q_B-(electron transfer mediators)), ABS/RC (absorption flux per RC (per Q_A reducing PSⅡreaction center)), TRo/RC (trapped energy flux per RC), ETo/RC (electron transport flux per RC) had been measured. The results showed that:For the photosynthetic parameters, the photosynthetic parameters of three Pinus trees were significantly different (P<0.05) and P_n was the largest with P. densiflora seedlings. P_n, T_r and E_WUE of P. thunbergii decreased with the shading degree increasing; P_n of P. tabuliformis reached maximum under 46% shading degree with T_r and E_WUE reaching maximum under 81% shading degree; Pn, T_r and E_WUE of P. densiflora showed no obvious differences. For the chlorophyll fluorescence kinetics parameters, the I_abs, Sm, Ψ_O, Ψ_RE, ABS/RC, TRo/RC, ETo/RC under different shading degree of the three Pinus trees were significantly different (P<0.05). I_abs, S_m, Ψ_O, Ψ_RE, ABS/RC, TRo/RC and ETo/RC of P. thunbergii had the same rule with the photosynthetic parameters; I_abs, Ψ_O, Ψ_RE, ABS/RC, TRo/RC and ETo/RC of P. tabuliformis reached maximum under 46% shading degree with S_m reaching maximum under 81% shading degree; The chlorophyll fluorescence kinetics parameters of P. densiflora wasn't significantly different when the shading degree changed (P>0.05). In general, P. densiflora had the strongest ability of using weak light and could adapted to various light environments; P. thunbergii grew well with enough light while P. tabuliformis grew well in light shaded gap.