两种杂交杨叶绿素荧光特性及光能利用

 比较研究了伊犁地区两种杂交杨伊犁杨1号(Populus deltaids ‘cv-64’ (P64))和伊犁杨小叶杨(P. simonii canaden×P. russkii-9 (Jia))对太阳辐射光能的利用和耗散特性。两种杂交杨光合速率(Pn)的日变化均呈现双峰型, 高光量子通量密度(PFD)阶段P_n达到20.1%的差距; 实际最大光化学猝灭ΦPSII日变化均呈“U”型, 于16:30时, P64的ΦPSII达到最低值, 而Jia的值于14:30时达到最低(Jia＞P64); 光合系统的闭合程度(L)在14:30时均出现一个短暂回落, 全天平均闭合程度无显著差异(p＞0.05)。非光化学猝灭系数(NPQ)在16:30同时达到最大值(Jia＞P64), 两者NPQ全天相差31.7%。叶片转化吸收太阳能热能耗散(E.D)和光化学反应转化的光能量(E.P)进行估算表明: 在PFD较低的环境条件下, 两种杂交杨将吸收的光能50%以上用于光化学猝灭; 在PFD较高的环境条件下, P64的E.P值比例大于Jia, 两者全天的E.P值没有太大的差异, P64的E.D值显著大于Jia的E.D值(p＞0.01), 而P64的E.D值占全天转化能量的比例小于Jia。P64和Jia的E.P达到最大的估算值时, 其E.D也达到了最大。分析结果表明: 两种杂交杨对高光能形成不同的适应机制, P64利用更多的太阳能进行光化学猝灭反应, 而Jia利用更多的太阳能进行非光化学猝灭反应, 减缓强太阳辐射伤害; 两种杂交杨用于光化学能量分配的比例P64大于Jia, 而Pn值在强辐射阶段和全天平均值、累积值均出现Jia＞P64。结果证明, 仅通过杂交杨本身叶绿体对光的荧光特性反应计算接收到的光能中有多少能量被利用与实际植物光合速率的转化的干物质存在一定的差异, 两种杂交杨光化学实际固定碳和转化光能的多少的内在关系需进一步的研究。

LIGHT ENERGY UTILIZATION AND CHLOROPHYLL FLUORESCENCE IN TWO CROSSBREED POPLARS

Aims Our objective was to study two widely planted hybrid poplars, Populus deltoids 'cv-64' (P64) and P. simonii canaden×P. russkii-9 (Jia), to explore their growth mechanisms and the solar energy utilization by photosystem II (PSII) antennae to thermal energy dissipation and photosyn-thetic electron transport characteristics during long-term adaptation to the ambient environment. Methods We studied energy utilization by computing chlorophyll fluorescence parameters and photosynthesis. Plants were grown at the Plain Forest Farm Nursery of the State Forestry Bureau of Ili Autonomous Prefecture in China's Xinjiang region.Important findings The diurnal changes of net photosynthesis (P_n) were bimodal and had a 20.1% gap under high photon flux density (PFD). The actual efficiency of open PSII centers (ΦPSII) were all of the "U" type, and their average values were equal. The ΦPSII of P64 and Jia reached the minimum value at 16:30 and 14:30, respectively. The closure value had one wave hollow at 14:30, and there was no significant difference (p>0.05) in whole-day average values. The non-photochemical quenching coefficients (NPQ) all achieved the maximum value at 16:30. Jia's NPQ maximum was less than that of P64, and the whole-day NPQ difference reached 31.7%. The estimated rates of photochemistry (E.P) and non-photochemistry (E.D) showed that under the lower PFD the poplars used more than 50% of the absorbed solar energy for the photochemical quenching, and under high PFD the absorbed solar energy for P64 for the photochemical quenching is greater than the proportion for Jia, while the absorbed solar energy for P64 for heat dissipation is less than the proportion for Jia. The E.P had no difference and reached the maximum estimated value when its E.D reached the maximum. P64 tended to use more absorbed solar energy for photochemical quenching, but Jia tended to use more solar energy for non-photochemical quenching. The cumulative values and average values of the P_n for Jia were much larger than values for P64, but the absorbed solar energy of P64 is greater than the proportion of Jia for the photochemical quenching. These results prove that it is inadequate to calculate the absorbed energy only by the chloroplast fluorescent characteristics of light received.