大田棉花叶片光合特性的研究

以Li- 6 40 0便携式光合测定系统对大田棉花叶片光合特性的研究发现 ,抗虫棉 33B不同叶龄叶片的光合日变化皆呈双峰曲线 ,可见明显的光合“午休”现象 ,但“午休”出现早晚、持续时间因叶龄而异。光照、温度和CO2 浓度皆对棉花的光合作用有显著的影响。棉叶的光补偿点与叶龄有关 ,老叶 (>45天 )较低 ,幼叶 (<15天 )较高 ,功能叶 (15～ 30天 )界于二者之间 ,无论老叶还是幼叶 ,其光饱和点皆高于 2 10 0 μmol·m-2 ·s-1;棉花光合中CO2 补偿点约为 80 μmol/mol,饱和点约为 110 0 μmol/mol;光合的最适温度为 2 5～ 30℃ ,且最适温度与光照强度的变化无关 ;叶龄 15～ 30天的净光合速率 (Pn)最大 ,老叶和幼叶的Pn较小。同一光强下以倒 5叶的Pn最高 ,并见Pn随叶位上升急剧降低而随叶位下降缓慢下降的现象 ,叶位间的光合差异不完全是由叶龄的差异所致

Photosynthetic characters of field grown cotton leaves

Photosynthetic characters of field grown cotton leaves were studied with Li-6400 portable photosynthesis, one of the most advanced systems for photosynthetic study The results showed that net photosynthetic rate (NPR) in leaves of various ages for transgenic cotton 33B appeared in curvilinear changes with double peaks and apparent middy depression diurnally, however, the start time and the duration of NPR middy depression were different among leaves with different leaf ages in a shinning day Light intensity, air temperature and CO 2 concentration evidently affected NPR The compensation point of CO 2 was related to the leaf age, old leaves with minimum CO 2 compensation point and young leaves with maximum CO 2 compensation point All the tested leaves, no matter whether they were old or young, had light saturation points more than 2100 μmol·m -2 ·s -1 Cotton leaves had a CO 2 compensation point of 80 μmol/mol and saturation point of 1100 μmol/mol The optimum temperature for photosynthesis was between 20 and 30℃,which had nothing to do with light intensity Cotton leaves at the ages of 15～30 days had higher NPR than those of the older or younger It was also found that the fifth leaf from the top in a cotton plant had the highest NPR, while the upper leaves dropped evidently and the lower leaves dropped gradually in NPR Leaf age was not the only cause of NPR difference among different leaves