Turkington Roy, Hamilton Ruaraidh Sackville, Gliddon Chris
Department of Botany, The University of British Columbia, V6T 2B1, Vancouver, B.C., Canada.
Unit of Plant Population Biology, School of Biological Sciences, University College North Wales, LL57 2UW, Bangor, Gwynedd, North Wales.
Oecologia. 1991 Apr;86(2):183-192. doi: 10.1007/BF00317530.
Genets of Trifolium repens (white clover) were collected from three patches of old permanent pasture dominated by Agrostis capillaris, Holcus lanatus or Lolium perenne. Plants derived from the genets were grown with plants of one grass species present on one side of each T. repens, and a different grass species on the other side, in all combinations of two of the three grasses. Different modules (a node with its associated internode, leaf, and axillary bud) on the same clover plant responded independently to the microenvironment provided by their own neighbouring grasses. In contrast, all apical meristems on the plant reacted similarly, showing a unified response and integrating the effects of the different microenvironments experienced by the whole clover plant. This is consistent with what is known both physiologically about the nutrition of meristems and modules, and ecologically about the exploratory growth habit of the species. Averaged over all associated grasses, there was no significant variation in the final dry weight of the different clover genets but these differed in their growth habit response to different grasses. In response to Agrostis as a neighbour, each meristem of T. repens rapidly produced many small modules. New modules were produced more slowly and were larger when Holcus or Lolium was the neighbour. The same pattern of differences occurred among clovers sampled from different backgrounds. Either genetic differences paralleled plastic responses, or plastic changes in phenotype that developed in response to different neighbours in the field persisted in the greenhouse. Plants taken from backgrounds of different grass species showed different responses to growing with those grass species. The differences were manifest primarily in a "positive leading diagonal" effect of Holcus or not-Holcus. They were the result primarily of differences in the dry weight per module and the probability of development of the axillary bud into a branch. This confirms earlier results, and implicates the central importance of branching as a means of local response to the microenvironment.
白三叶草（Trifolium repens）的无性系从三片以毛细翦股颖（Agrostis capillaris）、绒毛草（Holcus lanatus）或多年生黑麦草（Lolium perenne）为主的古老永久性牧场采集而来。从这些无性系培育出的植株，与三种草中两种草的所有组合进行种植，在每株白三叶草的一侧种植一种草，另一侧种植另一种不同的草。同一株三叶草上的不同模块（一个节点及其相关的节间、叶片和腋芽）对其相邻草提供的微环境有独立反应。相比之下，植株上所有顶端分生组织的反应相似，表现出统一的反应，并整合了整个三叶草植株所经历的不同微环境的影响。这与在生理上关于分生组织和模块营养的已知情况以及在生态上关于该物种探索性生长习性的情况是一致的。在所有相关草种上进行平均后，不同白三叶草无性系的最终干重没有显著差异，但它们对不同草种的生长习性反应不同。作为邻居时，对白三叶草的每个分生组织而言，当黑麦草为邻居时，它会迅速产生许多小模块。当绒毛草或多年生黑麦草为邻居时，新模块产生得更慢且更大。从不同背景采集的三叶草之间也出现了相同的差异模式。要么遗传差异与可塑性反应平行，要么在田间对不同邻居做出反应而产生的表型可塑性变化在温室中持续存在。从不同草种背景采集的植株在与那些草种一起生长时表现出不同的反应。差异主要体现在绒毛草或非绒毛草的“正主对角线”效应上。它们主要是每个模块干重以及腋芽发育成枝条的概率差异的结果。这证实了早期结果，并表明分支作为对微环境的局部反应方式具有核心重要性。
