Response of physiological integration in the clonal herb Zoysia japonica to heterogeneous water conditions

Physiological integration may be an important ecological strategy for clonal plants living in heterogeneous environments. The physiological integration between Zoysia japonica parent and offspring ramets under different experimental water conditions was examined. We applied four treatments: (1) both the parents and offspring were well watered, (2) both experienced drought, (3) the parents were well watered and the offspring experienced drought, and (4) the parents experienced drought and the offspring were well watered. The growth, chlorophyll content, photosynthesis, chlorophyll fluorescence, and antioxidant enzymes of Zoysia japonica were measured. The chlorophyll contents, chlorophyll a/b ratio, and photosynthetic parameters (Pn, Gs) of offspring ramets were not reduced when parents under well-watered conditions and offspring ramets under drought conditions suggested that the physiological support provided by parents enabled their offspring to maintain photosynthetic efficiencies. The support provided to the offspring by their parents was also obvious in the antioxidant systems and proline accumulation of Zoysia japonica in heterogeneous water environments. Physiological integration was not detected when the parents experienced drought and the offspring were well watered. The parents provided physiological support to their offspring and did not expense significant benefits through physiological integration when parents were well watered and offspring experienced drought. When the opposite conditions were true, physiological integration did not exist.