锥连栎不同叶龄叶片光合特征研究

Photosynthetic Characteristics on Different-aged Leaf of Quercus franchetii

以我国西南地区特有种锥连栎为试材,使用LI-6400便携式光合作用测定系统对锥连栎当年生叶和一年生叶的光合参数日进程以及光响应曲线进行测定。结果表明,(1)全光照环境下,锥连栎当年生叶和一年生叶的净光合速率(Pn)日变化呈'M'形双峰曲线,且当年生叶光合作用能力明显强于一年生叶,第1个峰值出现在1000,第2个峰值出现在1400,中午有明显的'午休'现象;气孔导度(Gs)、蒸腾速率(Tr)的日变化趋势与Pn较为一致;胞间CO2浓度(Ci)日变化与Pn日变化趋势大致相反,呈'W'形,中午Ci增加,表明净光合速率午间降低主要是受非气孔限制因素影响。(2)相关性分析显示,当年生叶Pn与Tr具有极显著正相关关系(P<0.01),一年生叶Pn与Gs、Tr具有极显著正相关关系(P<0.01)。(3)锥连栎当年生叶的最大净光合速率(Pnmax)、光饱和点(LSP)都较高且均高于一年生叶,表明当年生叶对强光有更高的适应能力,而当年生叶和一年生叶的光补偿点(LCP)都较低且表现为一年生叶的LCP低于当年生叶,一年生叶表现出更强的耐荫性,更接近于阴生植物的特性。

The seedlings of Qercus franchetii which is endemic to southwest China,were cultivated at full light for two years.The diurnal variations of photosynthesis and parameters of current-year leaves and one-year old leaves of Q.franchetii were determined.The results indicated that:(1)Under the full light level,the diurnal variations of net photosynthetic rate(Pn)of current-year leaves and one-year old leaves of Q.franchetii showed an'M'-shaped double-peak curve,and the Pn of current-year leaves was significantly higher than that of one-year old leaves.The first and second peaks occurred at 10:00 and 14:00 respectively.There was a significant'midday depression'of photosynthesis phenomenon at noon.The diurnal variation of stomatal conductance(Gs)and transpiration rate(Tr)were both similar with Pn;The diurnal variation of intercellular CO2 concentration(Ci)was roughly opposite to the diurnal variation trend of Pn,and showed a'W'shape.The increasing of Ci at noon indicated that the midday decreasing of net photosynthetic rate was mainly affected by non-stomatal limiting factors.(2)Correlation analysis showed that Pn had a significant positive correlation with Tr at P<0.01 level of current-year leaves,and Pn had a significant positive correlation with Gs and Tr at P<0.01 level of one-year old leaves.(3)The maximum net photosynthetic rate(Pnmax)and the light saturation points(LSP)of current-year leaves of the Q.franchetii were both higher than those of one-year old leaves.It indicated that the current-year leaves adapted well to high light.The light compensation points(LCP)of current-year leaves and one-year old leaves were low,while LCP of one-year old leaves was lower than that of current-year leaves.The one-year old leaves showed stronger shade-tolerance and were similar to the characteristics of shade plants.