半夏光系统对光照和温度日变化的适应

Adaptation of Pinellia ternate photoreaction system to diurnal changes of light and temperature

关键词:  半夏, 光照, 温度, 光系统, 叶绿素荧光参数

Key words:  Pinellia ternate, light, temperature, photoreaction system, chlorophyll fluorescence parameters

摘要:

为探讨半夏(Pinellia ternate)光系统对光照强度和温度日变化的适应机理,该文连续3 d模拟了在同一种变化的光照强度(0～1 600 μmol·m^-2·s^-1)日变化下低温(10～18 ℃)、中温(20～28 ℃)和高温(28～38 ℃)的环境条件,测定了光系统Ⅱ(PS Ⅱ)和光系统I(PS Ⅰ)的叶绿素荧光参数,通过PS Ⅱ和PS Ⅰ光合活性和电子传递能力的变化来研究半夏光合系统对光照强度和温度日变化的适应。结果表明:(1)PS Ⅱ最小荧光(F_o')和PS Ⅱ反应中心激发能捕获效率(F_v'/F_m')随光照强度的增加而降低,光照强度的增加是导致光系统的活性降低的主要原因,低温会进一步导致光系统活性的降低;(2)光照强度和温度的增加使PS Ⅰ受体端热耗散效率[Y(ND)]上升,而PS Ⅰ供体端热耗散效率 [Y(NA)]则降低,光照强度的增加不会导致供体侧较大的激发压,但会使受体侧开始积累较大的激发压,而较低的温度会导致受体侧活性降低,使供体侧积累较高的激发压;(3)高光(光强>900 μmol·m^-2·s^-1)对半夏的光抑制和光损伤导致了PS Ⅱ实际光化学量子产量 [Y(Ⅱ)]和PS Ⅰ实际光化学量子产量 [Y(I)]的降低,低温进一步加剧了Y(Ⅱ)和Y(I)的降低;(4)在高光下,PS Ⅰ的电子传递速率ETR(I)的增加启动了环式电子传递(CEF),较高的CEF稳定了高温下的PS Ⅱ电子传递速率ETR(Ⅱ)的同时也保护PS Ⅱ免受光的损伤;(5)在3 d的处理中,虽然非光化学猝灭系数(NPQ)随光照强度的增加而上升,但是相对于高温,在低温处理下,半夏较低的NPQ使PS Ⅱ非调节性能量耗散的量子产量 [Y(NO)]一直处于最高水平,表现出明显的光抑制。综上结果表明,低温降低了半夏对高光环境的适应能力,而高温通过增强NPQ,加速CEF的产生,减少光抑制的产生,从而加速光反应的电子传递和维持光反应系统的稳定性。因此,低温胁迫会加剧半夏光系统的损伤,适当提高温度可以增强半夏光反应系统对高光的适应性。

Abstract:

In order to explore the adaptation mechanisms of Pinellia ternate photoreaction system to daily variations of light intensity and temperature, we simulated the low temperature(10-18 ℃), moderate temperature(20-28 ℃)and high temperature(28-38 ℃)under the diurnal variation of the same light intensity(0-1 600 μmol·m^-2·s^-1)for three consecutive days, and the chlorophyll fluorescence parameters of Photosystem Ⅱ(PS Ⅱ)and Photosystem I(PS Ⅰ)were measured. The adaptation of photosynthetic system to diurnal changes of light intensity and temperature in P. ternata was researched by detecting the changes of PS Ⅱ and PS Ⅰ photosynthetic activity and electron transfer capacity. The results were as follows:(1)Minimal fluorescence intensity at actinic light(F_o')and photochemical efficiency of PS Ⅱ in the light(F_v'/F_m')was decreased with increased light intensity, and the low temperature further led to the F_v'/F_m' decrease and the F_o' increase.(2)PS Ⅰ donor end heat dissipation efficiency [Y(ND)] increased with the increase of light intensity and high temperatures, PS Ⅰ acceptor end heat dissipation efficiency [Y(NA)] decreased with the increase of light intensity and high temperatures.(3)Effective photochemical quantum yield of PS Ⅱ [Y(Ⅱ)] and the quantum yield of PS Ⅰ [Y(I)] were inhibited by high light(> 900 μmol·m^-2·s^-1),and the low temperature further significantly decreased Y(Ⅱ)and Y(I).(4)The increasing electron transport rate ETR(I)of the PS Ⅰ under the high light initiated the ring electron transfer(CEF), and the higher CEF stabilized the electron transfer rate ETR(Ⅱ)of the PS Ⅱ at high temperatures.(5)The non-photochemical quenching coefficient(NPQ)increased with the increase of light intensity, low NPQ keeps the quantum yield of non-regulated energy dissipation in PS Ⅱ [Y(NO)] on its highest level at low temperature. These results suggest that high temperature will reduce the photo-inhibition of P. ternata under high light by enhancing NPQ and CEF, accelerating the electron transfer and stability of the light reaction, in sharp contrast of low temperature. Therefore, low temperature can aggravate the damage of photoreaction system, and moderate temperature promotes the adaptation of plant photoreaction system to high light.