Abstract:

The changes of ionic absorption, secretion and the activity of POD on Aeluropus pungens under salinity conditions and the effects of silicon nutrition on those indices were studied using light microscopy, cytochemical localization, and quantitative and qualitative analysis for ions and physiological indices. The results were as follows: Under salinity conditions, the Na+ content increased and the Ca2+ content of the plant tissues decreased, while the other ions remained constant, and the concentrations of silicon in leaves increased with increasing salinity. The rate of ion secretion increased between 0 and 60 mmol·L-1 NaCl, and then declined when the NaCl concentrations in the roots reached 120 mmol·L-1. The content of soluble protein was unaffected but the POD activity was enhanced by the salt treatment. The amount of soluble proteins were higher in the roots than that in the leaves, while on the POD activity, the situation was the contrast. The water content did not change within 120 mmol·L-1 NaCl. The cytochemical location of Si distribution and POD activity techniques showed silica was distributed in rows along the leaf veins on the leaf surfaces, and some traces on the papillaes. On the salt glands Si accumulated on the top of the cap cell where the strong POD activi ty was found. By analyzing the elements, it was found that silicon tended to accumulate on the tissues of Aeluropus pungens. The Na content and the selective of Na, K of the shoots, which was not affected under 120 mmol·L-1 NaCl, was reduced under 60 mmol·L-1 NaCl by the addition of 3 mmol·L-1 Na 2SiO3. However, the Na content remained unaffected in the roots by the addition of Silicon to both salt concentrations. The above experiments demonstrated that halophyte Aeluropus pungens adapted to salinity conditions by adjusting water conditions, the ion distribution and POD activity on the plant tissues. The capacity of salt tolerance was improved, which was due to the inhibition of the Na transport from roots to shoots and the increasing abilities of antioxidative defense when silicon was added to the nutrient solutions.