琯溪蜜柚光合特性的研究

 利用Li-6400 光合作用仪对田间条件下7 年生琯溪蜜柚的光合特性进行了系统研究。结果表明: (1) 琯溪蜜柚外围叶片晴天的净光合速率(P_n) 日变化为双峰曲线, 首峰出现在8～10 时, 次峰值小于首峰值, 出现在14 时以后; 阴天呈单峰曲线; 内膛叶片P_n 日变化有双峰、单峰和锯齿形3 种类型。(2)观测期内P_n季节变化近似双峰曲线。(3) 不同月份和不同枝条叶片Pn 对光和CO₂ 响应有较大差别, 光补偿点和饱和点分别为16～46 和1 026～1 656μmol·m^-2·s^-1 , 表观量子效率0.01725～0.05431 ; CO₂ 补偿点和饱和点分别为51～80 和822～926μmol·mol ^-1 , 羧化效率0.01769～0.05191 ;P_n对CO₂ 的响应进程近似双曲线。(4) P_n与气孔导度、蒸腾速率、光照强度正相关, 与胞间CO₂ 浓度负相关, 与温度、湿度和叶面水气压亏缺的相关性比较复杂。(5) P_n 与叶片的叶绿素含量和比叶重之间没有明显相关性。(6) 光合适温为24～34 ℃。

Studies on Photosynthetic Characteristics of Guanximiyou Pomelo Variety

The photosynthetic characteristics of leaves in 7-year-old guanximiyou pomelo variety under field conditions were studied by using the Li-6400 portable photosynthesis system. The results were as follows : (1) The diurnal variation of net photosynthetic rate (P_n) of peripheral leaves in sunny days presented bimodal carve , the first peak occurred at 8:00- 10:00 , P_n was 15.77μmol·m^-2·s ^-1 , the second peak occurred after 14:00 , the value was lower than the first one ; In overcast days , the daily change of P_n had one peak , the value approach the first peak value of P_n in sunny days ; in both sunny and overcast days , the diurnal variation of P_n of inner leaves showed the one or two peak or indention carve. (2) The seasonal variation of P_n also approach bimodal carve by the average of P_n. (3) Among shoots in different months , there were differences in the responses of leaves P_n to light intensity and CO₂ . The light compensate and saturated point of leaves was 16～46μmol·m^-2·s ^-1 and 1 026 - 1 656 μmol·m^-2·s ^-1 respectively , the apparent quantum efficiency between 0.01725 and 0.05431 , these showed that the leaves of guanximiyou had the higher utilization efficiency on weak light and in strong light ; the CO₂ compensate and saturated point was 51 - 80μmol·mol - 1 and 822 - 926μmol·mol ^-1 respentively , the carboxying efficiency between 0.01769 and 0.05191. (4) P_n had obvious positive relationship with Cond , Trm and PAR, most of them were obvious or remarkable. P_n had obvious negative relationship with Ci , majority of them were remarkable. There were complex relationship between P_n and Tair , Tl , RH , Vpdl . (5) There were no marked relation between P_n and the chlorophyll content and specific leaf weight (SLW) of leaves. (6) The proper temperature of photosynthesis were 24 - 34 ℃.