杨梅光合作用的低温光抑制

Chilling-induced Photoinhibition of Photosynthesis in Myrica rubra Leaves

摘要:

利用便携式调制叶绿素荧光仪和光合作用测定系统研究了短期低温光照对杨梅幼树光合作用的影响。结果表明，低温光照处理后，杨梅叶片的Pn（净光合速率）、Gs（气孔导度）、Fv／Fm（最大的光系统Ⅱ光化学效率）、qP（光化学猝灭系数）和①PSⅡ（光系统Ⅱ的量子产量）下降，Ci／Ca（细胞间隙CO₂浓度／环境CO₂浓度）、Fo（初始荧光）、qN（非光化学猝灭系数）和（Fi—Fo）／（Fp—Fo）（失活的PSⅡ反应中心数量）上升。此外在同一水平低温下，中等强光（350 μmol m^-2s^-1）加剧了PSⅡ反应中心的失活或破坏并且需要更长时间来恢复。这些结果说明低温和有光照条件下引起的杨梅光合作用下降是由于光合机构活性下降所致，即主要是PSⅡ反应中心的失活或破坏：我们推测Q_A^-（还原态质体醌A）和非还原Q_B（质体醌B）数量的积累可能是导致PSⅡ反应中心失活或破坏的原因，在低温光抑制过程中非辐射能量耗散对保护光合机构起着重要作用。

Abstract:

Gas exchange and chlorophyll fluorescence were investigated in young Chinese strawberry tree （Myrica rubra var. astropurea Tsen.） leaves treated with different chilling temperatures （12℃. 6℃ and 2℃） under differentirradiance levels （0, 70 and 350 μmol m^-2s^-1） for 12 hours by a portable photosynthesis system HCM-1000 and a portable modulation fluorometer PAM-2000. The results showed that exposure of strawberry tree leaves to various low temperature and light resulted in the increases in Ci/Ca （internal/external CO₂ concentration）, Fo （initial fluorescence）, qN （non-photochemical quenching） and （Fi-Fo）/（Fp-Fo） （amount of inactive PS Ⅱ centers）, butdecreases in Pn （net photosynthesis rate）, Gs （stomata conductance）, Fv/Fm （maximal photochemical efficiency of PSⅡ）, qP （photochemical quenching） and ФPSⅡ （quantum yield of PS Ⅱ ）. At the same levels of low temperature, moderate irradiance （350 μmol m^-2s^-1） enhanced the inactivation or damage of PSⅡ reaction centers which needed longer time for recovery. It was shown that the inhibition of photosynthesis in treated plants induced by low temperature under light condition can be attributed to the loss of activity in photosynthetic apparatus. It is suggested that the accumulation of QQ_A^- and non-reducing Q_B is a possible cause for the inactivation or damage of PSⅡ reaction centers, and non-radiative energy dissipation probably plays an important protective role against the photoinhibition induced by chilling.