Welham Clive V, Turkington Roy, Sayre Cindy
Department of Botany, University of British Columbia, V6T 1Z4, Vancouver, BC, Canada.
Oecologia. 2002 Jan;130(2):231-238. doi: 10.1007/s004420100791. Epub 2002 Jan 1.
Heterogeneity in resource distribution has been an important selective force shaping morphological plasticity in plants. When resources are patchily distributed, changes in morphology are assumed to affect placement of the resource-acquiring structures (roots and leaves) such that they enhance the plant's capacity for resource uptake. Morphological development of four white clover (Trifolium repens) genets was studied in two glasshouse experiments. In the spatial experiment, two substrates (potting soil and sand) were used to create the following discrete patch combinations, sand-sand, soil-sand, sand-soil, and soil-soil. Stolons grew across each combination and consecutive ramets from a given stolon permitted rooting in each substrate pair. In the temporal experiment, the two ramets were first rooted in sand only. After a predetermined period, the sand was replaced and the same substrate combinations created as in the spatial experiment. In each experiment, total developmental time within a given substrate combination was held constant. All measurements were conducted on the second (i.e., younger) of the ramet pairs. In the spatial experiment, ramets rooted in soil had significantly greater branching frequencies than ramets rooted in the sand substrate, regardless of genotype or the preceding substrate type. Ramets occupying the sand-sand combination had the lowest branching frequencies but branch production for the ramet rooted in sand was higher if the preceding ramet was rooted in soil. The substrate occupied by a preceding ramet had no influence upon branching propensity if a ramet was rooted in soil. There were no significant differences in branching frequencies between the sand and soil substrates in the temporal experiment. The relationship between branching and substrate thus depended upon whether a ramet was exposed to a given substrate type during its early development. In both experiments, branched ramets in the soil-soil combinations had significantly greater shoot mass than corresponding ramets in the sand-sand combinations. Internode length was significantly shorter in the soil versus sand combinations of the spatial experiment but was unaffected by substrate in the temporal experiment. Leaf area and stolon width showed significant genotype×treatment interactions in both experiments but no consistent trends were evident; petiole length was unaffected by substrate.
资源分布的异质性一直是塑造植物形态可塑性的重要选择力量。当资源呈斑块状分布时，形态变化被认为会影响资源获取结构（根和叶）的布局，从而增强植物吸收资源的能力。在两个温室实验中研究了四个白三叶草（Trifolium repens）无性系的形态发育。在空间实验中，使用两种基质（盆栽土和沙子）创建了以下离散斑块组合：沙-沙、土-沙、沙-土和土-土。匍匐茎穿过每种组合，来自给定匍匐茎的连续分株允许在每个基质对中生根。在时间实验中，两个分株首先仅在沙子中生根。在预定时间段后，更换沙子并创建与空间实验中相同的基质组合。在每个实验中，给定基质组合内的总发育时间保持恒定。所有测量均在分株对中的第二个（即较年轻的）上进行。在空间实验中，无论基因型或先前的基质类型如何，在土壤中生根的分株的分支频率明显高于在沙子基质中生根的分株。占据沙-沙组合的分株分支频率最低，但如果前一个分株在土壤中生根，则在沙子中生根的分株的分支产生较高。如果分株在土壤中生根，前一个分株占据的基质对分支倾向没有影响。在时间实验中，沙子和土壤基质之间的分支频率没有显著差异。因此，分支与基质之间的关系取决于分株在其早期发育过程中是否暴露于给定的基质类型。在两个实验中，土-土组合中的分支分株的地上部质量明显大于沙-沙组合中的相应分株。在空间实验中，土壤与沙子组合中的节间长度明显较短，但在时间实验中不受基质影响。在两个实验中，叶面积和匍匐茎宽度均显示出显著的基因型×处理相互作用，但没有明显的一致趋势；叶柄长度不受基质影响。
