Huber Heidrun, Hutchings Michael J
Department of Plant Ecology & Evolutionary Biology, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands e-mail:
School of Biological Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK, , , , , , GB.
Oecologia. 1997 Nov;112(4):485-491. doi: 10.1007/s004420050336.
Previous studies have shown that internodes and petioles of closely related erect and stoloniferous species show marked differences in their response to shading. Vertical structures show strong elongation responses while horizontal structures show significantly smaller elongation responses. This paper reports an experiment designed to test whether internodes and petioles on orthotropic (vertically oriented) and plagiotropic (horizontally oriented) shoots produced by the same plant, also show such differential responses. The study species, Glechoma hirsuta, produces plagiotropic shoots in its vegetative stage and orthotropic shoots during its generative stage. Shoots of G. hirsuta were grown either in full daylight or under simulated canopy shade. Internode and petiole elongation, biomass investment patterns and other growth-related parameters were measured on plants in each light treatment. In orthotropic shoots the length of internodes responded more strongly to shading than the length of petioles, while the opposite was true for plagiotropic shoots, confirming the hypothesis that vertical spacers have higher degrees of shade-induced plasticity than horizontally oriented spacers. Growth and development of horizontally oriented shoots was reduced by shading, whereas that of vertically oriented shoots was unaffected by light treatment. The results are discussed in terms of the differences in function of vertically and horizontally oriented spacers, and the probable benefits of plasticity in enhancing essential activities including photosynthesis, habitat exploration and seed dispersal.
先前的研究表明，亲缘关系相近的直立型和匍匐型物种的节间和叶柄在对遮荫的反应上存在显著差异。垂直结构表现出强烈的伸长反应，而水平结构的伸长反应则显著较小。本文报告了一项实验，旨在测试同一植株产生的直立型（垂直定向）和斜生型（水平定向）枝条上的节间和叶柄是否也表现出这种差异反应。研究物种糙叶水苏在营养阶段产生斜生型枝条，在生殖阶段产生直立型枝条。糙叶水苏的枝条在全日照或模拟树冠遮荫条件下生长。对每种光照处理下的植株测量节间和叶柄的伸长、生物量分配模式及其他与生长相关的参数。在直立型枝条中，节间长度对遮荫的反应比叶柄长度更强烈，而在斜生型枝条中情况则相反，这证实了垂直间隔物比水平定向间隔物具有更高程度的遮荫诱导可塑性这一假设。遮荫降低了水平定向枝条的生长和发育，而垂直定向枝条的生长和发育不受光照处理的影响。本文从垂直和水平定向间隔物功能的差异，以及可塑性在增强包括光合作用、栖息地探索和种子传播等基本活动方面可能带来的益处进行了讨论。
