遮荫对甜瓜叶片光合特性的影响

Photosynthetic Characteristics of Shading Melon Leaves

以适宜不同栽培条件的3个甜瓜品种为材料,研究了遮荫对其光合色素含量、净光合速率及比叶重等叶片特性的影响。结果表明:与正常光照相比,遮光处理能诱使甜瓜叶片叶绿素和类胡萝卜素含量显著提高,叶绿素a/b显著降低。全光照条件下,3个甜瓜品种的净光合速率日变化曲线均呈双峰型,有明显的"光合午休"现象,而在遮荫条件下则呈单峰曲线变化,且光合峰值出现的时间比全光照下推迟;遮光条件下甜瓜叶片气孔导度日变化曲线与其净光合速率日变化类似。3个品种间比叶重在全光照条件下差异不显著,但遮荫显著降低了壮龄叶片的比叶重,且遮荫强度越重,比叶重越小;品种‘黄河蜜3号’壮龄叶的比叶重降幅(31.83%)显著大于‘银帝’(27.22%)和‘玉金香’(26.01%)。可见,遮荫降低了甜瓜叶片的净光合速率和功能叶片的比叶重,植株通过增加自身叶片光合色素含量以增强对环境的适应性,缓解遮荫对其的影响,品种‘银帝’表现出较强的耐弱光性。

Three cultivars of Cucuznis rnelo L., differing in suitable cultivation models, were employed to study the effects of light intensity on leaf characteristics, such as photosynthetic pigment content, net pho- tosynthetic rate （Pn） and specific leaf weight （SLW） etc. The results indicated that shading treatment in- duced melon leaf chlorophyll and carotenoids （Car） contents increased and Chl a/b deceased significantly in comparison with normal light intensity. Under full light, the diurnal change of net photosynthetic rate （Pn） of three melon cultivars showed clear midday depression,but only a single delayed peak under shading con- ditions. The diurnal change oI stomatal conductance （Gs） of melon leaves was similar to P,. Under full light,the differences of SLW among melon cultivars were not significant, but SLW of melon leaf was re markably reduced under shading conditions, and SLW under 260/4o of natural light treatment dropped signif- icantly,the SLW decrease of ＇ Huanghemi 3＇ （31. 83 %） was significantly higher than those of ＇ Yindi＇ （27.22 % ） and ＇ Yujinxiang＇ （26.01%）. It could be seen that shading treatment reduced net photosynthetic rate of melon leaves and specific leaf weight of functional leaves. The photosynthetic pigment content of plant would be increased in order to alleviate the influence of shade and enhance the adaptability to the en vironment. Yindi showed the stronger low light intensity tolerance.