| The salt-secreting mangrove, Aegiceras corniculatum and non-salt-secreting mangrove, Kandelia candel or Bruguiera gymnorrhiza were cultivated in sand with various salinities (0‰,10‰, 20‰, 30‰) 40‰> 50‰). This paper studied the responses of photosynthetic rate, transpiration rate and some signal molecules such as H2O2, Ca2+ and cAMP to different salinities by using the methods such as gas exchange technique, protoplast separation, fluorescence probe labeling and radioactive isotopes technique etc. The results showed as following:1 The effects of salinity on the germination of leaves and the total root length in K. candel hypocotyl are distinctive, and that is maximal in 10‰ salinity, while the salinity has nearly no effect on the germination and the total numbers of the roots.2 The effects of salinity on photosynthetic rate in K.candel and A.corniculatum seedlings cultivated in salinity for different days are distinctive. After Cultivated for 10 days, salinity has almost no effect on photosynthetic rate in K.candel seedlings, but in A.corniculatum seedlings,photosynthetic rate increased steadily within 20‰ salinity and decreased steadily above 20‰ salinity. In the seedlings of both mangroves cultivated for 20 days, photosynthetic rate of K.candel decreased within 30‰ salinity and increased above 30‰ salinity, while in A.corniculatum, photosynthetic rate increased within 40‰ salinity and decreased above 40‰ salinity. Photosynthetic rate is similar in response to salinity in K.candel and A.corniculatum seedlings cultivated for 30 days, that is, increased within 10‰ salinity and decreased above 10‰ salinity; The effects of salinity on transpiration rate are also different for the two mangroves cultivated for different days. After cultivated for 10 days, transpiration rate of K.candel seedlings decreased within 20‰ salinity and increased above 20‰ salinity, while in A.corniculatum seedlings, transpiration rate has the decreasing trend all along within 50‰ salinity. After cultivated for 20 days, transpiration rate decreased within 50‰ salinity in K.candel, but that in A.corniculaum seedlings changes small. After cultivated for 30 days, transpiration rate of K.candel seedlings increased within 20‰ salinity, and decreased above 20‰ salinity, while in A.corniculatum seedlings, transpiration rate increased within 10‰ salinity and decreased above 10‰ salinity.3. For K.candel, MDA concentration in the roots decreased within 30‰ salinity, and increased above 30‰ salinity, while MDA concentration in theinleaves decreased within 20‰ salinity, and increased after that. The effects of salinity on SOD activity is similar in the roots and leaves, that is, low salinity(root within 30‰,leaf within 10‰)increased SOD activity and high salinity (root above 30‰, leaf above 10‰)decreased SOD activity; For A.corniculatum, MDA concentration in the roots keep steady relatively within 30‰ salinity while suddenly increased above 30‰ salinity, and MDA concentration in the leaves decreased within 20‰ salinity, and suddenly increased after that. The SOD activity in the roots increased steadily within 20‰ salinity and decreased above 20‰ salinity, while the SOD activity in the leaves increased 10‰ salinity and decreased suddenly within 10‰~~20‰ salinity and increased steadily above 20‰ salinity. All the results indicated that the effects of salinity on membrane lipid peroxidation have some differences in both mangroves.4 In K.candel seedlings, H2O2 contents in the roots decreased steadily within 20‰ salinity and increased above 20‰ salinity, while H2O2 contents in the leaves decreased steadily within 30‰ salinity and increased above 30‰ salinity; In A.corniculatum seedlings, H2O2 contents in the roots decreased within 30‰ salinity and increased above 30‰ salinity, while H2O2 contents in the leaves decreased steadily with the increasing of salinity within 50‰ salinity. All the results showed that the effects of salinity on H2O2 contents in the roots and... |
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