Preliminary Studies On Allelopathic Potentials Of Spartina Alterniflora On Mangrove Plants

This paper evaluated systematically the potential of allelopathy for Spartina alterniflora by treating with different concentrations of S. alterniflora aqueous extracts (SAAE) on cabbage, cucumber, and radish. The effects of different concentration of SAAE on Aegiceras corniculatum, Avicennia marina and Bruguiera gymnorrhiza; and the mix-cultured effects of different densities of S. alterniflora with Kandelia candel seedlings were studied. In these experiments, the germination of propagule, the growth and physiological characteristics of seedlings were measured. The results are described as follow:1. Compared to the control, the germination speed of cabbage, cucumber, and radish seeds were affected by the different concentration of SAAE. The seedlings height and roots length for cucumber seedlings were increased under treatments with low concentration of SAAE, while other concentrations of SAAE inhibited the roots length of receptor plants. And the inhibition were promoted with high concentration of SAAE. The most serious inhibition appeared in the 0.4 g·ml-1 SAAE treatment for the above-ground biomasses, and 0.3 g·ml-1 SAAE treatment for the underground respectively.2. The growth of receptor plants were significantly inhibited by the treatment with high concentration of SAAE, however, the inhibition effect was weakened and even because a promotion effect as the SAAE concentration decreased.3. The high concentration of SAAE reduced the Pn, Gs and Tr in A. corniculatum leaf, and significantly inhibited the activities of SOD and POD, while promoted the MDA content; these led to the abnormal balance between the activity of anti-oxidant enzymes and peroxidation of membrane lipids, and then decreased biomass for A. corniculatum seedlings.4. The chlorophyll and sugar content of A. marina leaf decreased with the increasing of SAAE concentration, and so did the activities of SOD and POD; however, the free proline and MDA content increased as the SAAE increased.5. The 0.05 g·ml-1 SAAE treatment increased the chlorophyll content in B. gymnorrhiza leaf, and promoted the content of sugar and starch too. But the growth of B. gymnorrhiza seedling didn't change obviously in other treatments.6. The stem height and biomass of K. candel seedlings were promoted at mix-cultured with low density of S. alterniflora, while those mix-cultured with high density were inhabited. As the density of S. alterniflora increased, the Pn, Gs, Tr, WUE, contents of chlorophyll and protein, activities of SOD and POD in K. candel seedlings all decreased. On the contrary, Ci, the content of sugar, starch, proline, free amino acids and MDA content increased with the increasing of density of S. alterniflora. These physiological changes promoted the anti-stress abilities in K. candel seedlings to counteract the adverse effects from S. alterniflora.