异质性光对野牛草叶片解剖结构的影响

Effects of light heterogeneity on leaf anatomical structure in Buchloe dactyloides

自然界中植物生长所需资源通常呈异质性分布,具有发达匍匐茎的野牛草(Buchloe dactyloides)在蔓延过程中相连克隆分株常生活在异质性的光环境中。有研究证明,在异质性光条件下,植株幼叶的叶片解剖结构受成熟叶所处光照条件的影响,而异质性光条件下克隆分株的叶片形态解剖结构是否也受相连分株所处光照条件的影响则未见报道。通过设置高光(全光照)和低光(遮阴)两个水平,对由匍匐茎相连的野牛草克隆分株施以同质和异质性光处理,研究了异质性光对野牛草叶片解剖结构的影响。结果发现:在异质性光环境中,遮阴的野牛草克隆分株的主脉直径、维管束鞘细胞个数、叶片厚度以及近轴侧和远轴侧叶肉细胞的厚度均显著降低;同质性的低光处理对这些指标则没有显著影响。在异质性光处理下,未遮阴姊株近轴侧和远轴侧叶肉细胞的厚度以及远轴侧的气孔大小显著增加,而未遮阴的妹株近轴侧和远轴侧叶肉细胞的厚度、气孔密度和气孔大小、叶片厚度和维管束鞘细胞个数则会降低。同质高光处理下克隆分株近轴侧和远轴侧的气孔密度和气孔大小显著高于同质低光。野牛草克隆分株近轴侧和远轴侧叶肉细胞的厚度、气孔密度和气孔大小受相连分株所处光照条件的显著影响。该研究结果表明:未遮阴的姊株因为与遮阴的妹株相连而显著受益,而未遮阴的妹株则因为与遮阴的姊株相连而损耗严重;在异质性光处理下,遮阴分株叶片形态上缩减的可塑性生长是为减少维持其存活的消耗,提高遮阴分株存活率的一种适应性表现。

Aims Essential resources for plant growth are usually patchily distributed. During the process of propagation, interconnected ramet pairs of stoloniferous plant buffalograss （Buchloe dactyloides） may therefore experience contrasting resource supply such as light. Under heterogeneous light supply, anatomical structure of newly developed leaves is regulated by the light condition of mature leaves. However, little is known about whether leaf anatomical structure of clonal ramets is affected by the light environment of interconnected ramets in clonal plants under heterogeneous light supply. Methods Two light levels were set, with high light （natural sunlight） and low light （shade, 10% natural sunlight）. Interconnected ramet pairs of buffalograss were exposed to homogeneous or heterogeneous light conditions. Important findings Main vein diameter, bundle sheath cell number, leaf thickness and adaxial/abaxial meso- phyll thickness of shaded ramets were remarkably decreased in spatially heterogeneous light environment; while no signifiacnt difference of these parameters was observed between ramets developed under homogeneous high light and low light conditions. Under heterogeneous light supply, adaxial/abaxial mesophyll thickness and abaxial stomatal size in unshaded elder daughter ramets （EDR） were remarkably increased, while adaxial/abaxial mesophyll thickness, stomatal density and size, leaf thickness, and bundle sheath cell number in unshaded younger daughter ramets （YDR） were reduced. Ramets under homogeneous high light conditions had higher stomatal den- sity and larger stomata than those under homogeneous low light conditions. Adaxial/abaxial mesophyll thickness, stomatal density and size in buffalograss ramets were significantly affected by the light conditions of intercon- nected ramets. Conclusions Unshaded EDR benefit from their connection to shaded YDR, while unshaded YDR experience marked cost due to its connection to shaded EDR. The plastic decrease of shaded ramets under heterogeneous light may be associated with its reduced survival cost, and elevated survival rate under shading.