氮肥施用量对莴笋光合特性影响的研究

运用盆栽试验方法，研究了氮肥施用量对作物（莴笋）光合特性的影响。结果表明，不同的氮肥施用量不仅对莴笋产量具有较大的影响，而且在一定程度上影响莴笋的光合速率、光饱和点、光补偿点、叶绿素含量等光合特性。增施氮肥，使其光合速率、光补偿点、叶绿素含量均得到提高，但过量施用氮肥反而会导致光合特性向不利方向变化并引起莴笋产量的下降。

EFFECTS OF PHOTOSYNTHETIC CHARACTERISTIC OF LETTUCE AND NITROGEN APPLICATION

By using the test method of pot planting, author has studied the influence of N application rate on photosyrithetic characteristic of lettuce. The study indicates that N application rate has influenced on not only yield of lettuce but also photosynthetic rate,light saturation point, light compensation point and chlorophyll content etc. When N application rate reaches up to about N₃ level (N, 0. 15g/kg), the yield of lettuce turns out to be maximum. Any more N application rate beyond this level will otherwise lead to the decrease of yield of lettuce. Based on the outcome of the test, the relation between N application rate(X) and yield of lettuce (Y) can be obtained as follows:Y-8. 98+35. 101X-62. 779X₂ Although content and photosynthetic rate etc. go up as N application rate increase,light saturation point reaches up to its maximum value 636μ mol. m^-2·s^-1 when N application rate is N₃ level. That is, the utilization of strong light is more efficient. This is consistent with the change trend of yield.