三种地宝兰属植物叶片解剖结构及光合特性的比较研究

Comparative study on leaf anatomical structures and photosynthetic characteristics of three Geodorum species

关键词:  地宝兰属, 气孔特征, 光合日变化, 光响应曲线, CO₂响应曲线, 叶绿素

Key words:  Geodorum, stomatal characteristics, daily variation of photosynthesis, light response curve, CO₂ response curve, chlorophyll

摘要:

为探讨地宝兰属植物的叶片解剖结构及光合特性,该研究对狭域濒危种贵州地宝兰(Geodorum eulophioides)及广布种地宝兰(G. densiflorum)、大花地宝兰(G. attenuatum)的叶片解剖结构、光合日变化、光响应曲线、CO₂响应曲线、叶绿素含量等指标进行测定。结果表明:(1)3种地宝兰属植物的叶肉细胞没有海绵组织和栅栏组织分化,气孔仅分布于下表皮; 与地宝兰和贵州地宝兰相比,大花地宝兰具有更大的叶片厚度和较小的气孔密度,表现出更适应弱光环境的结构特征。(2)3种地宝兰属植物的净光合速率(P_n)日变化均呈“双峰型”曲线,其光合“午休”主要由非气孔限制引起; P_n和水分利用效率(WUE)日均值大小均表现为大花地宝兰>地宝兰>贵州地宝兰,表明贵州地宝兰积累光合产物的能力更弱,对干旱环境的适应能力可能更差。(3)3种地宝兰属植物均为阴生植物,地宝兰的光补偿点(LCP)最小、光饱和点(LSP)最大,对光强适应范围较宽; 大花地宝兰具有较高的最大净光合速率(P_max)和表观量子效率(AQY),其光合能力较强; 贵州地宝兰的P_max和潜在最大净光合速率(A_max)最小,其光合能力和对CO₂的利用能力更弱。(4)地宝兰和大花地宝兰的叶绿素a(Chl a)、叶绿素b(Chl b)和总叶绿素(Chl)含量均显著(P<0.05)高于贵州地宝兰。(5)3种地宝兰属植物的叶片厚度、叶肉厚度、叶绿素含量与P_max间存在显著(P<0.05)相关性。综上认为,与地宝兰和大花地宝兰相比,贵州地宝兰的光合能力和适应性较差,这可能与其濒危有很大关系; 适当遮阴和增加CO₂浓度有利于3种地宝兰属植物的光合作用。该研究结果为贵州地宝兰濒危原因的分析及3种地宝兰属植物种质资源保育提供了参考依据。

Abstract:

To explore leaf anatomical structures and photosynthetic characteristics of Geodorum plant, the anatomical structure of leaves, daily variation of photosynthesis, light response curve, CO₂ response curve, chlorophyll content and other indexes of the narrowly endangered Geodorum eulophioides and widely spread G. densiflorum and G. attenuatum were measured. The results were as follows:(1)Three species of Geodorum did not have spongy and fenestrated tissue differentiation in their chloroplasts, and stomata were distributed only in the lower epidermis. Compared with G. densiflorum and G. eulophioides, G. attenuatum had a greater leaf thickness and smaller stomatal density, exhibiting structural characteristics that were more adaptable to low light environments.(2)The daily changes of net photosynthetic rate(P_n)of three species of Geodorum showed a “bimodal” curve, and the photosynthetic “lunch break” was mainly caused by non-stomatal limitation. The daily mean values of P_n and water use efficiency(WUE)showed that G. attenuatum > G. densiflorum > G. eulophioides, which indicated that G. eulophioides had a weaker ability of accumulating photosynthesis products, and its adaptive capacity to the arid environment was probably poorer.(3)Three species of Geodorum were all shade plants. G. densiflorum had the smallest light compensation point(LCP)and the largest light saturation point(LSP), and had a wider range of adaptation to light intensity; G. attenuatum had a high maximum net photosynthetic rate(P_max)and apparent quantum efficiency(AQY), and its photosynthetic capacity was stronger; G. eulophioides had the smallest P_max and the potential maximum net photosynthetic rate(A_max), and its photosynthetic capacity and CO₂ utilization capacity were weaker.(4)The chlorophyll a(Chl a), chlorophyll b(Chl b)and total chlorophyll(Chl)contents of G. densiflorum and G. attenuatum were significantly(P<0.05)higher than those of G. eulophioide.(5)There were significant(P<0.05)correlations between the leaf thickness, mesophyll thickness, chlorophyll content, and P_max of three species of Geodorum. It was concluded that the photosynthetic capacity and adaptability of G. eulophioides were poorer compared with G. densiflorum and G. attenuatum, which might be greatly related to its endangerment; appropriate shading and increased CO₂ concentration favored photosynthesis in three species of Geodorum. The results of this study provide a reference for the analysis of the endangered causes of G. eulophioides and the conservation of germplasm resources of three Geodorum species.