水稻耐低锌基因型的生长发育和若干生理特性研究

在不同Zn2+活度（pZn2+9.7，pZn2+11.0和pZn2+＞11.5）的溶液培养条件下，研究了水稻耐低锌基因型的生长发育和若干生理特性。结果表明:水稻锌营养存在明显的基因型差异，降低锌离子活度会增加地下部于物质的积累，当Zn2+活度从pZn2+9.7下降到pZn2+11.0时，耐低锌品种的地上部干重虽下降，但因地下部干重显著增加，故总干重相近;锌敏感品种则地上部干重显著下降，而地下部干重增加不明显，总干重显著下降。当严重缺锌（pZn2+＞11.5）时，所有基因型水稻的干重构极显著地下降，但锌敏感品种比耐低锌品种下降得更多。降低Zn2+活度使水稻秧苗的出叶速度减慢，在极度缺锌条件下，敏感品种只能生长到3.5叶，而耐低锌品种能生长到4.5叶左右。对叶绿素和根系氧化力的测定结果表明，轻度缺锌或缺锌初期会使叶绿素含量上升和根系氧化力下降，但严重缺锌时，则使叶绿素含量显著降低，而使根系氧化力明显增加。锌敏感品种比耐缺锌品种的变化更为明显。锌离子活度对秧苗的含水量也有明显的影响。因此，耐低锌基因型在低Zn2+活度条件通过保持较低的根氧化作用，促进根系生长以维持地上部新叶生长，达到低锌适应稳态。

STUDIES ON GROWTH AND SOME PHYSIOLOGICAL CHARACTERS OF Zn-EFFICIENT RICE GENOTYPES AT DIFFERENT Zn2+ ACTIVITIES

Six rice cultivars with different Zn efficiency were cultivated at different Zn²⁺ activities (pZn²⁺9. 7, pZn²⁺11.0 and pZn²⁺>11. 5) in nutrition solution. Their growth and some physiological characters were studied in responses to different Zn²⁺ activities. It was found that the ability of rice tolerance to Zn deficiency significantly differed among the rice cultivars. Dry matter(DW) accmulation of roots increased when Zn²⁺ activities were lower than pZn²⁺ 11. 5 for all the cultvars tested. However,Shoot DW of Zn-efficient rice genotypes significantly decreased but their root DW significantly increased when pZn²⁺ decreased from 9. 7 to 11.0. Shoot DW of Zn-inefficient rice genotypes significantly decreased and no increase in root DW were observed when pZn²⁺ decreased from 9. 7 to11.0 Therefore, the DW of whole plant for Zn-efficient rice. genotypes had not significantly decreased while that for Zn-inefficient rice genotypes had significantly decreased at relatively low Zn²⁺ activities.At pZn²⁺ > 11. 5, the DW of all rice genotypes significantly decreased, especially for Zn-inefficient rice genotypes. There were obvious differences in growth rates of leaves among the cultivars at low Zn²⁺ activities. The Zn-inefficient rice genotypes could only grow up to 3. 5 leaves and Zn-efficient rice genotypes could grow to 4. 5 leaves at pZn²⁺>11. 5. The chlorophyll content slightly increased at pZn²⁺ deceased up to 11.0, but decreased at pZn²⁺ > 11. 5. Root oxidizing power (ROP) considerably increased at severe Zn deficiency (pZn²⁺> 11.5]. At seedling age of 39, it was interesting that ROP decreased about one-fold for the Zn-efficient cultivars but increased markedly for Zn-inefficient cultivars when plants were grown at pZn²⁺11.0.The water content of rice seedling slightly decreased when Zn²⁺ activities decreased. It could be concluded that at relaive low Zn activity the Zn-efficient cultivars could increase root growth, lower root oxidizing power, maintain leaf growth rate and leaf photosynthetic capacity and thus reach homeostasis in adaptation to low Zn.