弱光胁迫对花生功能叶片RuBP羧化酶活性及叶绿体超微结构的影响

Effects of low light stress on rubisco activity and the ultrastructure of chloroplast in functional leaves of peanut

间作套种是我国主要的花生(Arachis hypogaea)种植方式之一。然而,与单作相比,在间作套种体系中,花生截获的光能较少,生长发育差,产量低,研究不同品种耐阴机理对选择适宜间作套种的花生品种具有重要意义。该研究用耐阴性不同的两个花生品种‘花育22号’(强耐阴性)和‘白沙1016’(弱耐阴性)为材料,在大田条件下采用不同透光率遮阴网设置50%自然光强(中度弱光胁迫)和15%自然光强(严重弱光胁迫)2个弱光处理,从出苗期开始遮阴40天,以自然光强为对照,研究了弱光胁迫对花生功能叶片RuBP羧化酶活性和叶绿体超微结构的影响。结果表明:光强为自然光照50%和15%的处理,‘花育22号’RuBP羧化酶活性与对照相比虽有降低,但差异不显著,而‘白沙1016’分别比对照低40.1%和59.4%,显著低于对照。与对照相比,50%自然光强下‘花育22号’叶绿体数不变,叶绿体基粒数和基粒片层数显著增多,叶绿体变长且发育完好,15%自然光强下,叶绿体数、基粒数和淀粉粒数显著减少,叶绿体膜和基粒片层出现破损,但叶绿体变长,基粒片层数增加;‘白沙1016’在50%自然光强下,叶绿体数目和超微结构变化同‘花育22号’相似,在15%自然光强下叶绿体变圆,基粒数的降幅和基粒片层破损程度大于‘花育22号’且基粒片层数减少,淀粉粒数增多。因此,弱光胁迫特别是严重弱光胁迫条件下,功能叶RuBP羧化酶活性降低幅度小、叶绿体超微结构受损程度低是‘花育22号’耐阴的光合生理基础。

Aims In recent years, intercropping system has become one of the major practice of peanut（Arachis hypogaea） cultivation in northern China because of the high land and energy utilization efficiency, to some extent compensating for the production loss caused by decreasing area of cultivation land. Intercropped peanut plants often have a lower pod yield compared with monoculture due to constraint on light availability. This study was conducted to explore the shade-tolerance mechanism in two peanut cultivars, ‘Huayu 22＇ and ‘Baisha 1016＇, that grew in an intercropping system, by studying chloroplast ultrastructure and rubisco activity under different levels of shading. Methods A field experiment was conducted with three levels of light treatments, including full natural light（CK）, 50% natural light indensity（NLI）, and 15% NLI. The ‘Huayu 22＇ was used as a shade-tolerant cultivar and the ‘Baisha 1016＇ as a shade-susceptible cultivar based on previous studies. Experimental plants of both cultivars were shaded for 40 days from emergency in 2006. Rubisco activity, the number and shapes of chloroplasts and starch grains, and number of grana and granum lamella were investigated in functional leaves of plants in all treatments. Important findings The functional leaves of peanut plants in the 50% and 15% NLI treatments had a lower rubisco activity than those in the CK treatment. In the ‘Baisha 1016＇, the reduction in rubisco activity was 40.1% in the 50% NLI treatment and 59.4% in the 15% NLI treatment, respectively, compared to the CK treatment;whereas no significant differences were found among treatments in the ‘Huayu 22＇ in the rubisco activity. Compared with the CK, the number of chloroplasts remained unchanged, the number of grana and lamella in grana increased, and the individual chloroplast was longer and in perfect development in the functional leaves of plants of the ‘Huayu 22＇ grown in the 50% NLI treatment. In contrast, the number of chloroplasts, grana and starch grains of the ‘Huayu 22＇ plants decreased significantly, the chloroplast membrane and grana lamella were damaged, the number of granum lamella increased, and the individual chloroplast became longer in the 15% NLI treatment. The number and ultrastructure of chloroplasts in the ‘Baisha 1016＇ plants followed similar patterns of changes as those of the ‘Huayu 22＇ in the 50% NLI treatment. For plants of the ‘Baisha 1016＇ in the 15% NLI treatment, their chloroplasts became more roundly shaped, with decreasing number of grana lamella and increasing number of starch grains, compared with the CK. There were a greater decrease in the grana number and more damage in the grana lamella in plants of the ‘Baisha 1016＇ than those of the ‘Huayu 22＇. In conclusion, the shade tolerance of the ‘Huayu 22＇ resulted from lack of changes in rubisco activity and less damage in the ultrastructure of chloroplasts when under low light stress compared with the ‘Baisha 1016＇.