遮阴对高山杜鹃叶片解剖和光合特性的影响

Effects of shading on photosynthesis and anatomical structure in leaves of Rhododendron

关键词:  高山杜鹃, 解剖结构, 光合, 光照

Key words:  Rhododendron, anatomical structure, photosynthesis, light

摘要:

为了解高山杜鹃对光能的需求和适应性,该研究以盆栽3 a生高山杜鹃品种cv. Furnivall's Daughter为材料,探讨了遮阴对高山杜鹃叶片解剖结构和光合特性的影响。结果表明:光照强度对高山杜鹃品种cv. Furnivall's Daughter叶片的气孔密度没有显著影响,其气孔密度范围在299.70～327.22个·mm^-2之间,但光照对气孔开度和单个气孔器的面积影响显著,100%全光照和30%全光照处理植株分别具有最小和最大的叶片气孔开度。在处理的光强范围内,随着光强减弱,叶片厚度、栅栏组织厚度、海绵组织厚度以及上、下表皮厚度逐渐降低,有利于提高叶片的光能利用效率。100%全光照处理下,高山杜鹃叶片的光饱和点(LSP)、净光合速率(P_n)、饱和光合速率(P_max)、气孔导度(G_s)、蒸腾速率(T_r)均较低,遮阴处理有效提高了P_n、P_max、G_s、T_r和光能利用效率(LUE),且30%全光照处理植株的叶片光补偿点(LCP)、暗呼吸速率(R_d)最低,而LSP、P_n、P_max、G_s、T_r和LUE最高。这表明高山杜鹃在云南昆明地区的最适光照条件是30%左右的全光照,在高山杜鹃的栽培及应用中,应采取适当的遮阴措施以满足其生长的最佳光照条件。

Abstract:

Rhododendron is a world famous ornamental garden plant and has significant economic and ornamental value. Light has an important impact on the growth and development of Rhododendron. However, the studies on the demand and adaptability of Rhododendron are scarce. In order to understand the demand and adaptability of Rhododendron to light, 3-year-old plants of Rhododendron cv. Furnivall's Daughter were used as materials and the effects of shading on leaf anatomical structure and photosynthesis were studied. The results were as follows: The impact of light intensity on the stomata density of Rhododendron cv. Furnivall's Daughter was not obvious, and the stomatal density ranged from 299.70 to 327.22 mm^-2. However, the stomatal size and the area of stomata apparatus were significantly influenced by light intensity. The plants of 100% and 30% full light intensities had the minimum and maximum stomatal size, respectively. As the light intensity decreased, the thickness of leaf, palisade tissue, sponge tissue, as well as the thickness of adaxial epidermis and abaxial epidermis decreased so as to improve the light use efficiency of leaves. The plasticity analysis showed that the plasticity index of mesophyll-related parameters such as leaf thickness, abaxial epidermis thickness, and the thickness of palisade and sponge tissue were higher, while that of stomatal-related parameters such as stomatal density, stomatal length and width were lower, which indicates that mesophyll tissue plays a more important role in the process of adaption to different light environments. The analysis of light response curves and photosynthetic parameters showed that the plants of 100% full light intensity were inhibited and damaged by strong light, and the plants showed the lowest light saturation point(LSP), net photosynthetic rate(P_n), photosynthetic rate at light saturation point(P_max), stomatal conductance(G_s)and transpiration rate(T_r). After shading treatments, P_n, P_max, G_s, T_r and light use efficiency(LUE)were improved. Compared with other shading treatments, the plants of 30% full light intensity not only had the lowest light compensation point(LCP), dark respiration rate(R_d), but also had the highest LSP, P_n, P_max, G_s, T_r and LUE. The above results suggest that the optimum light intensity of Rhododendron cv. Furnivall's Daughter in Kunming is about 30% full light intensity. In the cultivation and application of Rhododendron, we should take some shading measures to meet the optimum light conditions for its growth.