不同时间‘绿岭’核桃叶片光合和荧光特性的动态变化

Dynamic changes of photosynthetic and fluorescent characteristics in 'Lvling' walnut leaves at different stages

为给核桃优质高产栽培技术措施的制定提供科学依据,以‘绿岭’核桃为试材,分别在6、7、8月对其叶片的光合和荧光特性进行了观测与分析。结果表明:‘绿岭’核桃净光合速率的变化曲线在6、7月均呈单峰曲线,且在上午10:00时出现了最高峰,其峰值分别为10.25和11.32μmol·m^(-2)s^(-1);其在8月却呈双峰曲线,且出现在10:00时的第1次峰值大于出现在14:00时的第2次峰值;导致‘绿岭’核桃光合速率出现"午休"现象的主要因素是气孔限制因素。6、7月测定的初始荧光和电子传递速率的变化曲线均呈双峰曲线,8月测定的初始荧光和电子传递速率的变化曲线均呈单峰曲线,此时的光合有效辐射、温度、湿度等参数均发生了快速变化,导致PSⅡ反应中心受到一定程度的破坏。叶绿素a和叶绿素a+b的含量,均以6月测定的2.50与3.33 mg·g^(-1)为最高,极显著大于8月测定的2.04和2.76 mg·g^(-1),而与7月的测定值间均无显著差异。相关性分析结果表明:净光合速率与气孔导度、蒸腾速率间均呈极显著正相关,而与光合有效辐射和初始荧光值之间均有显著的正相关关系;初始荧光值与蒸腾速率、空气温度间均呈显著正相关,而与胞间CO_2浓度间呈显著负相关。文末分析认为,环境因素和叶绿素含量都是影响‘绿岭’核桃光合速率的主要因素。

In order to provide some scientific basises for making measures of fine quality and high-yield cultivation of walnut, using ＇Lvling＇ walnut as materials, photosynthetic and fluorescent characteristics of leaves were determined and analyzed in June, July and August. The results showed that net photosynthetic rate of ＇Lvling＇ walnut showed a single peak curve in June and July, the peak occurred at 10：00, and the peak values were 10.25 and 11.32μmol·m-2s-1, respectively. It showed a bimodal curve in August, and the first peak at 10：00 was higher than the second peak at 14：00. The main factor that led to the ＂midday depression＂ phenomenon of photosynthetic rate in ＇Lvling＇ walnut was stomatal limitation. Initial fluorescence values and electron transfer rates showed double peak curves in both July and July. But the indexes showed single peak curves in August, the photosynthetically active radiation, temperature and humidity were rapidly changed at this time, and it lead to a certain damage to the PS II reaction center. The contents of chlorophyll a （2.50 mg/g） and chlorophyll a ＋ b （3.33mg/g） in June were the highest, the values were extremely significantly higher than those in August （2.04 and 2.76 mg/g） and had no significant differences with the deminated values in July. The results of correlationanalysis showed that net photosynthetic rate had extremely significant positive correlation with stomatal conductance and transpiration rate, and had significant positive correlation with photosyntheticlly active radiation and initial fluorescence value. Initial fluorescence value had significant positive correlation with transpiration rate and air temperature, and had significant negative correlation with intercellular CO2 concentration. In summary, environmental factors and chlorophyll content were the main factors influencing photosynthetic rate in ＇Lvling＇ walnut.