Physiological Responses Of Three Mangrove Species Seedlings To Low Temperature Stress And Allelopathy Of Aquatic Extract Of Spartina Alterniflora

In order to achieve good establishment it is essential that the newly planted seedlings can survive their first winter where they may be susceptible to cold temperatures. The species planted included a native species (Kandelia candel) and two alien ones, Leguncalaria racemosa from Mexico and Sonneratia apetala from Bangla Desh. We measured a range of physiological attributes in the leaves of seedlings of the three species over winter (early-October2010to late-February2011), the measurements included:soluble sugar and free proline concentrations, SOD, POD and CAT activities, O2-generation rate, MDA and relative electrical conductivity. Over the entire monitoring period, the leaf soluble sugar concentrations of all three mangrove species seedlings increased then decreased; Kcandel had the greatest concentrations and L. racemosa the least. The rate of O2-generation from the leaves of K. candel showed a similar response to the sugar concentrations; S. apetala and L. racemosa on the other hand exhibited the same initial increase but the high rates were maintained at significantly greater rates than K. candel (p<0.01). However, SOD, POD and CAT activities showed the opposite response (p<0.01), with POD and CAT activities in the leaves of L. racemosa and S. apetala seedlings declining significantly in late winter. Free proline concentrations of L. racemosa were higher than that of K. candel and S. apetala; all increased as air temperature reduced. The contents of MDA and relative electrical conductivity of all three plant species increased as minimum daily air temperature decreased. L. racemosa and S. apetala seedlings had significant higher level of MDA than K. candel seedlings (p<0.01), but there was no obvious difference between L. racemosa and S. apetala seedlings (p>0.05). The relative electrical conductivity of K candel seedlings was significantly lower than that of L. racemosa and S. apetala seedlings (p<0.01).The effect of infusion of each Spartina alterniflora organs on the growth of3mangrove species are generally characterized by promoting in low concentration and inhibiting in high concentration.Infusion of each Spartina alterniflora organs can promote the chlorophyll content in seedling leaves of Kandelia candel but promoting in low concentration and inhibiting in high concentration during apply both on the seedling of Sonneratia apetala and Leguncalaria racemosa. Antioxidant enzyme activities of the Seedling leaves or roots of3mangrove species were enhanced by infusion of each Spartina alterniflora organs but inhibited when the concentration was high. MDA content in leaves or roots were increased with the increasing of infusion concentration.