Patterns Of Water Physiological Integration And The Phenotypic Plasticity In Zoysia Japonica Steud., A Clonal Plant

Physiological integration as an adaptive strategy of clonal plant has been paid attentions by ecologists. Water is a most important resource for the growth and development of plants. Water physiological integration is one of the most important parts of clonal integration of clonal plants. The patterns of water physiological integration of Zoysia japonica were studied applying the technique of stable isotope (H₂¹⁸O), and the phenotypic plasticity of Zoysia japonica were also studied through the treatments of different soil moisture and the experiments of stolon-severing and connection.In the environment with heterogeneous and homogenous soil moisture, in comparison with the severed stolons, several morphological indexes of the intact stolons were promoted, such as the diameter of main stolon, total length and biomass of new stolon, number of new ramets, leaf area and specific leaf area. However, branching intensity were reduced in the stolon-severing treatment. The results suggest water physiological integration exist under the environments with both heterogeneous and homogenous soil moisture. Water absorbed by roots translocated both acropetally and basipetally.In the environment of homogenously high soil moisture, water physiological integration benefited the whole plant. However, in the environment of homogenously low soil moisture, although the water physiological integration significantly increased branching intensity and number of new ramets, total biomass of new ramets reduced greatly.When ramets located in the habitat with heterogeneous soil moisture, water sharing occurred among the connected ramets. The growth and development of the ramets located in the patch with high soil moisture were at some cost, but those of ramets in the patch of low soil moisture benefited from the water integration.In the environment with heterogeneous soil moisture, the branching intensity of the ramet fragment located in the patch of low soil moisture were higher than that of the corresponding fragment in the habitat with homogenous low soil moisture. The clone growth in the habitat with heterogeneous soil moisture decreased than that in the habitat with homogenous soil moisture, which might attribute to the special treatments in the experiments.In the environment with heterogeneous soil moisture, when stolons maintained intact, waterpotentials of the ramets in the patch of high soil moisture were significantly higher than those in the low soil moisture. In the environment with homogeneous high or low soil moisture, when stolons maintained intact, water potentials of the basal ramets were higher than those of the apical ramets, which revealed the existence of water physiological integration with acropetal direction. When stolons were severed, water potentials of the apical and basal ramets changed independently, and the water potentials became almost same.In the environment with heterogeneously high and homogeneously low soil moisture, the translocation of H₂¹⁸O absorbed by the basal and middle ramets in root, stolon and leaf of the main stolon showed both strong acropetal and basipetal trends. In the former environment, the translocation of H₂¹⁸O reduced at first several ramets but then increased in the successive ramets; In the latter environment, the translocation of H₂¹⁸O increased continuously in acropetal direction. Acropetal translocation of H₂¹⁸O tended to be the main direction in the main stolons. Water physiological integration tended to be extensive in the stolons of Zoysia japonica.In the environment with heterogeneous and homogeneous soil moisture, H₂¹⁸O distributed mainly in the leaves. In the environment with heterogeneously high and homogeneously low soil moisture, the translocation of H₂¹⁸O in series of roots, stolons, A leaves and B leaves in the secondary stolons showed similar acropetal tendency. H₂¹⁸O arrived apexes of the secondary stolons. ¹⁸O in A leaves were usually significantly higher than those in B leaves.