Morpho-anatomical and physiological responses of two Dendranthema species to waterlogging

The responses to waterlogging of the two Dendranthema species D. nankingense (Nakai) Tzvel. and D. zawadskii (Herb.) Tzvel. contrast considerably. Although the stress induced wilting and leaf chlorosis in both species, symptoms were more apparent and appeared earlier in the intolerant D. nankingense. In the more tolerant D. zawadskii, adventitious roots formed above the flooding level, and aerenchyma developed in the root, stem and leaf. The D. zawadskii palisade parenchyma was thicker, and larger intercellular spaces developed in the spongy mesophyll. The activities of alcohol dehydrogenase, pyruvate decarboxylase and lactate dehydrogenase were enhanced in roots of both species following the imposition of stress. In D. zawadskii the rise in ADH activity was more pronounced, while D. nankingense showed a significantly higher LDH activity. The activities of superoxide dismutase, ascorbate peroxidase and catalase were all higher in the leaves of D. zawadskii than in D. nankingense, and the leaves of D. nankingense showed a higher content of malondialdehyde throughout the period of waterlogging. Photosynthesis was decreased in both species, and there was a significant fall in the intercellular CO2 concentration in D. zawadskii. These data suggested that the greater relative waterlogging tolerance of D. zawadskii appears to depend on a combination of metabolic and morpho-anatomical responses.