不同光照条件下喜阴植物谢君魔芋对稳态和动态光源的响应特征

Steady-state and dynamic photosynthetic performance in the shade-demanding plant Amorphophallus xieiunder different levels of growth irradiance

关键词:  谢君魔芋, 光合作用, 光合诱导, 氮分配, 光照条件

Key words:  Amorphophallus xiei, photosynthesis, photosynthetic induction, nitrogen partitioning, growth irradiance

摘要:

谢君魔芋(Amorphophallus xiei)是起源于云南西南地区热带雨林的典型喜阴植物,近年来得到了广泛种植和推广,在种植过程中,谢君魔芋需要采用遮荫栽培模式。为了揭示谢君魔芋对光照强度的适应策略,该研究探讨了生长在不同光照强度下(透光率为50%、29%、17%、7%)谢君魔芋叶片的光合作用特征、光合诱导特征、光合色素含量以及叶片氮素(N)含量和N分配。结果表明:随着生长环境光照强度的降低,单位叶面积和单位叶质量最大净光合速率、光合色素含量、最大羧化速率、最大电子传递速率及比叶面积均增大,而暗呼吸和光补偿点均减小。在光合诱导过程中,生长在透光率为17%光环境中的谢君魔芋完成50%光合诱导所需的时间最短,约为81.4 s; 在光诱导进行10 min时,诱导状态最高,为87.3%。完成50%和90%光合诱导所需的时间与低光下初始气孔导度呈负相关关系。随着生长光照强度降低,叶片中的N分配到羧化组分和生物能转化组分中的比例先增大后减小,在透光率为17%的光环境下具有最大值; 而叶片中的N分配到捕光色素组分中的比例随着生长环境光照强度降低而增加。该研究结果表明,喜阴植物谢君魔芋通过加强对低光和动态光源的利用能力及有效的N资源分配策略来适应低光照环境。

Abstract:

Amorphophallus xiei is a typically shade-demanding plant that originates from the tropical rainforest located in southwest of Yunnan Province. In the agricultural production, A. xiei is commonly cultivated under the shade condition. The photosynthetic performance, photosynthetic induction characteristics, photosynthetic pigment, and leaf nitrogen(N)partitioning were examined in A. xiei grown along a light gradient, and the purposes of the present study were to reveal the adaptive mechanism to growth irradiance levels. Area- and mass-based maximum net photosynthetic assimilation rate(A_max), photosynthetic pigment content, maximum carboxylation rate, and maximum electron transport rate as well as specific leaf area significantly increased with decreasing growth irradiance levels; however, dark respiration rate and light compensation point decreased significantly. In the process of photosynthetic induction, the induction time to reach 50% of A_max was the shortest(81.4 s)and the induction state of 10 min was the highest(87.3%)in the individuals grown under the 17% of full sunlight. Moreover, there was a negative correlation between the induction time to reach 50% and 90% of A_max and the initial stomatal conductance across all the treatments. The fraction of leaf N allocated to carboxylation and bioenergetics firstly increased and then decreased with the decreasing growth irradiance levels, and the maximum values were recorded in individuals grown under 17% of full sunlight; at the same time, the fraction of leaf N allocated to light-harvesting components increased significantly with decreasing growth irradiance levels. These results suggested that the typical shade-demanding plants A. xiei acclimate to low growth irradiance by enhancing the capacity of leaf to utilize low light and dynamic light, and by adopting the strategy of N resource allocation that might efficiently overcome light shortage.