Effect Of Drought Stress On The Osmotic Adjustment Materials Of Heavenly Bamboo (Nandina Domestica) In Different Soil Types

The distribution of Karst landscape is very general in the world, especially in the southwest of China. In limestone districts, ecological environment is more and more severe due to low water retention capacity, low productivity and growing rocky desertification. It is urgent to carry out vegetation restoration and ecological restoration in limestone desertification districts.The goal of this paper is to give some advices on vegetation restoration and ecological restoration of limestone desertification districts based on the comparative research on the osmotic adjustment mechanism of heavenly bamboo in two soil types. Heavenly bamboo (Nandina domestica ) , growing commonly in limestone districts, was planted to pots in two soil types(black limestone soil and purple soil) under four different water resistances (adequately, mildly, moderately, and severely watered). The experiment lasted for one month. Both before and after the treatment, the contents of soluble sugar, free proline, free amino acid, Ca²⁺ and Mg²⁺ in roots, stems and leaves were measured. The results are as follows:1. Before the treatment, the contents of soluble sugar in black limestone soil were lower than those in purple soil, where the contents of free proline were higher. And the contents of free amino acid in roots and leaves were higher, but those in stems were lower in black limestone soil. The contents of Ca²⁺ were higher, as well. But the contents of Mg²⁺ in two soil types were various.2. The contents of soluble sugar, free proline, free amino acid and Ca²⁺ in black limestone soil were affected very much under drought stress. But the contents of Mg²⁺ were not affected significantly. Compared with adequately watered, the accumulations of soluble sugar and free proline in roots, stems, and leaves showed significant differences in different water resistances( P <0.05). The accumulations of free amino acid and Ca²⁺ in roots and stems showed significantdifferences in different water resistances, while the contents of Ca2+ in leaves did not show significant differences. The contents of free amino acid in leaves decreased gradually, and showed significant differences in mildly and severely watered. The relative contributions of five osmotic adjustment materials were soluble sugar, free amino acid, Ca2+, free proline and Mg2* in turn.3. The contents of soluble sugar in purple soil were affected very much under drought stress, but free proline, free amino acid and Ca2+ were affected to some extent. The contents of Mg2* were not affected significantly. The contents of soluble sugar, free proline and free amino acid in roots, stems and leaves were various. Compared with adequately watered, the accumulations of soluble sugar in roots and leaves showed significant differences in different water resistances, but stems did not. The accumulations of proline in stems and leaves in mildly watered showed significant differences, but roots decreased gradually. The contents of free amino acid in roots, stems and leaves increased in mildly watered, then decreased gradually and showed significant differences in different water resistances. The accumulations of free amino acid in stems showed significant differences in mildly watered .The relative contributions of five osmotic adjustment materials were the same as those in black limestone soil.4. The stems in both two-soil types showed excellent abilities on the accumulations of osmotic adjustment materials. While the roots and leaves showed different abilities in terms of soil types, different water resistances and osmotic adjustment material types.5. The research on the comparison of five osmotic adjustment materials between two soil types showed the contents of.soluble sugar were various. The accumulations of free proline and free amino acid in black limestone soil were more than those in purple soil along with more and more serious water resistances. The accumulations of Ca2+ and Mg2+in black limestone soil were more than those in purple soil. On the whole, the ability of osmotic adjustment in black limestone soil was higher than that in purple soil.