Effect of Light Intensity and Nutrient Availability on Clonal Growth and Clonal Morphology of the Stoloniferous Herb Halerpestes ruthenica

摘要

In a greenhouse experiment plasticity of clonal growth and clonal morphology of the Stoloniferous rosette herb Halerpestes ruthenica Ovcz. in response to differing levels of light intensity and nutrient availability was studied. Total plant dry weight, leaf area of primary ramets, total number of ramets and of stolons, and total stolon length were significantly reduced, while specific internode length and specific petiole length significantly increased under deep shading (6.25% of high light intensity, 5.3% of full daylight) or under low nutrient availability. Under low nutrient availability, mean stolon internode length of H. ruthenica was significantly larger while branching intensity and number of ramets smaller than those under high nutrient availability. These responses are consistent with the foraging model of clonal plants, indicating that H. ruthenica is able to forage nutrients through the plastic responses of clonal growth and clonal morphology when it grows in heterogeneous environments. However, under deep shading, both mean stolon internode length and mean petiole length were significantly reduced, which disagrees with the findings of many other Stoloniferous herbs in response to low or medium levels of shading (ca. 13% ― 75% of high light intensity, > 10% of full daylight), suggesting that under deep shading Stoloniferous herbs may not forage light through the plastic responses of spacer length. Many traits such as total plant dry weight, total number and length of stolons, total length of secondary and tertiary stolons, total number of ramets, leaf area of primary ramets and branching intensity were markedly influenced by the interaction effect of light intensity and nutrient availability. Under high light intensity nutrient availability affected these traits more pronouncedly, however under low light intensity nutrient availability either did not affect or affected less markedly on these traits, indicating that light intensity had significant effect on nutrient foraging in H. ruthenica. Under deep shading or low nutrient availability, H. ruthenica may increase its mean stolon internode length by means of thinning stolon internodes (i.e., an increase in specific internode length), which provides it with more chance to escape from resource-poor sites.