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日光温室黄瓜叶片的Pn和CE以中、上位较高 ,尤其是第 4位叶最高 ,顶部叶和中下位叶次之 ,下位叶最低 ,光合作用饱和光强也以中位叶最高 ,但光补偿点多随叶位的下降而降低 ,基部弱光和CE降低是导致下位叶Pn降低的主要原因。在黄瓜生长期内 ,各叶位叶片的Pn随PFD的升高而增大。不同叶位叶片Pn的日变化规律基本相同 ,均呈单峰曲线型 ,高峰出现在 12时左右。随着种植密度的增加 ,植株各层次叶片的光量子通量密度逐渐降低 ,尤其是中下部叶片降低幅度较大。种植密度对上位叶的Pn影响不大 ,但对光补偿点影响较大 ;下位叶的Pn及其饱和光强多随种植密度的增加而降低 ,但不同密度处理的光补偿点差异不显著。黄瓜叶片对光强有一定的适应和调节能力 ,表现为光照越弱 ,AQY越高 ,对光的利用能力越强。
In greenhouse, the Pn and CE of cucumber leaves were higher in middle and upper position, especially in the fourth leaf, the top leaf and the middle and lower leaf were the second, the lower leaf was the lowest, the photosynthesis saturated light intensity was also the highest in the middle leaf, but the light The compensation points mostly decreased with the decrease of leaf position, and the decrease of basal weak light and CE were the main reasons leading to the decrease of Pn in lower lobe. During the cucumber growth period, the Pn of leaves increased with the increase of PFD. The diurnal variation of Pn in leaves with different leaf positions were basically the same, showing a single peak curve with the peak at about 12 o’clock. With the increase of planting density, the light quantum flux density of the leaves of all the plants gradually decreased, especially in middle and lower leaves. The planting density had little effect on the Pn of the upper leaves, but had a greater effect on the light compensation points. The Pn and its saturation light intensity of the lower leaves mostly decreased with the increase of planting density, but the difference of light compensation points was not significant. Cucumber leaf light intensity has some ability to adapt and adjust the performance of the weaker light, AQY the higher the ability to use light the stronger.