Effects Of Clonal Integration On Plant Adaptation

Clonal plants can adapt to stressful environments and/or expand habitat by clonal integration. Based on clonal integration, many interesting works have be carried out. In current studies, we used Alternanthera philoxeroides (alligator weed) as materials to test the effect of integration on the adaptation to stressful habitat. The roles of clonal integration in plant growth on stress conditions and the adoption mechanisms to heterogeneous environments were investigated. Our results were followed:The first experiment we simulated on the expansion of Alternanthera philoxeroides from terrestrial to contaminated aquatic habitats, to test the roles of clonal integration during this process. When a stolon connection was severed, all distal ramets grown in the contaminated water died. When the stolon connection was intact, however, the survival rate of the distal ramets was 85%-100% when they were grown in the three lower levels of contamination treatments and 43.75% in the highest level. Moreover, the survival rate and growth of the distal ramets grown in the three lower levels of contamination treatments did not differ from those in the control (uncontaminated water).The second experiment we investigated the effects of clonal integration on the Alternanthera philoxeroides under homogeneous, stressful environments, i.e., under simulated acid rain and herbivory. The simulated acid rain treatments did not affect biomass of alligator weed, no matter whether the stolons were intact or severed. When the stolons were left intact, the mild acid rain treatment (pH=4.5) significantly increased total stolon length and number of ramets, suggesting that mild acid rain may improve plant growth. Despite the status of the stolons, the simulated herbivory treatments significantly decreased biomass, but increased number of leaves. When the stolon connections were lost, herbivory treatments significantly increased number of ramets of alligator weed.These results indicated that 1) clonal integration significantly increased the growth of clonal ramets on stress conditions, however, it played a limited role when they were subjected to severe stress by the high stress conditions; 2) alligator weed can well adapt to acid rain and herbivory stress, clonal integration plays a limited role under the homogeneous stressful environment.