摘要
晴天，田间水稻顶部完全展开叶最大的Ｐｎ出现在上午８时半左右。低钾营养加剧了“午睡”。８：３０～１４：３０高光强期间Ｐｎ与气孔导度和Ｃｉ分别呈显著直线正相关。Ｈｉｌｌ反应活力午后最低，但该时低钾水稻的Ｈｉｌｌ反应活力较钾充足水稻高。ＳＯＤ活力早晨最低，中午该酶活力增加程度在低钾水稻中更为明显。上述各项均存在着品种间的差异。因此，低钾下水稻“午睡”的加剧由低气孔导度所致，较长时间的低Ｃｉ会诱发低的Ｈｉｌｌ反应活力。
Two rice cultivars grown in pots with normal and low potassium supply were used to explore the cause of deeper midday depression of Pn under low-potussium condition. Maximum Pn occurred at about 8:30 when the photosynthetic photon flux (PPF) was about 1 200 μmol m-2 s-1 and was slightly higher in low-potassium plants than in normal plants. Under low-potassium condition the midday depression of Pn was deeper, partiularly, for cv. Erjiufeng, a cultivar more sensitive topotassium deficiency. Hill reaction rate stayed unchanged throughout the morning, fell at noon and rose again in late afternoon. The rate at noon was higher in the low-potussium plants.SOD activity was lower in early morning than at noon and afternoon and was also higher in low-potassium plants than in normal-potassium plants. Although a prolonged low Ci under strong irradiance can reduce PS Ⅱ activity reversibly, positive correlation of Pn with stomatal conductunce and Ci from 8:30 to 14:30 indicates that midday depression results from the lowering of stomatal conductance rather than from the low ering of Hill reaction rate. At noon the higher SOD activity in the low-potassium plants may be a mechanisum of avoidance of the damage from excessive PPF.
基金
农业部"八
五"课题资助
