蒙古沙冬青光合作用光能利用特征及其影响因子

The Characteristics and Limiting Factors of the Light-use Efficiency of Photosynthesis in Ammopiptanthus mongolicus

本研究通过测定自然条件下蒙古沙冬青(Ammopiptanthus mongolicus)叶片的叶绿素荧光,了解了其光能利用的日变化及季节变化特征,并分析了影响其光能利用特征的生态因子.结果显示,蒙古沙冬青叶片吸收光能用于光合作用的比例[实际光化学效率,Y(Ⅱ)]呈早晚高,午间低的趋势;用于可调节的能量耗散的比例[非调节性能量耗散量子产量,Y(NPQ)]则呈午间高,早晚低的趋势.一年之中,蒙古沙冬青Y(Ⅱ)3月最高,1月最低;其所吸收光能用于非调节性的能量耗散的比例[非调节性能量耗散量子产量,Y(NO)]则1月最高,3~9月均较低.相关性分析结果表明,Y(Ⅱ)和Y(NPQ)主要受光合有效辐射(PPFD)影响,其中Y(Ⅱ)随PPFD的增加而减少,Y(NPQ)随PPFD的增加而增加;Y(NO)主要受叶片温度(Tleaf)的影响,随Tleaf的降低而升高.以上结果表明,蒙古沙冬青光合作用的光能利用率同时受强光和低温的影响;强光条件下蒙古沙冬青主要依靠增加Y(NPQ)来消耗过剩光能,低温条件下主要依靠增加Y(NO)来消耗过剩光能.

Ammopiptanthus mongolicus is the only evergreen broad-leaved shrub in Alxa Plateau, China. In this paper, we studied the diurnal and seasonal patterns of the photosynthetic light-use characteristics in A. mongolicus by measuring its chlorophyll fluoresces in the field, and analyzed its relationships with environmental factors. We found that the proportion of light absorbed by photosys- tern （PS） Ⅱ that used for photochemistry [ Y （ Ⅱ ） ] in A. mongolicus was higher in early morning and late afternoon, comparing with midday; in contrast, the proportion of PSⅡ absorbed light that thermally dissipated via regulated non-photochemical quenching [ NPQ, Y （NPQ）] was higher in midday, comparing with early morning and late afternoon. Ammopiptanthus mongolicus showed high- est Y（Ⅱ） in March and lowest Y（Ⅱ） in January; meanwhile, the proportion of PSⅡ absorbed light that thermally dissipated via non-regulated NPQ [ Y（NO） ] was highest in January. The results of correlation analysis showed that Y（ Ⅱ ） and Y （NPQ） was mainly affected by photosynthetic pho- ton flux density （PPFD）, Y （Ⅱ） decreased with increased PPFD while Y （NPQ） increased with in- creased PPFD ; Y （ NO ） was mainly influenced by leaf temperature （ Tteaf ） and increased with de- creased Tleaf. These results suggested that the light-use efficiency of photosynthesis in A. mongolicus was affected by both high irradiance and low temperature; A. mongolicus primarily employed in- creased Y （NPQ） to deal with excess energy under high irradiance conditions and employed in- creased Y （NO） to cope with excess energy under cold conditions.