Abstract:

Soil in southern China is acid and red, P deficiency and Al toxicity commonly coexist on this kind of soil. It is one of the important limiting factors on rice production in southern China. In order to elucidate Al-tolerance of Yuexiangzhan, an elite indica cultivar which was widely planted in South China, the experiment of aluminum and pH on root formation and growth in germination and seedling stage was undertaken in simple CaCl2 solution by using Al-tolerant japonica cultivar, Nipponbare, as a control. In the process of seed germination, Al inhibited seed root formation and growth significantly (F=123.84,P<0.000 1). However, the differences in sensitivity to Al stress at the stage of primary root formation between Yuexiangzhan and Nipponbare were not significant. Seedling root elongation was affected by solution pH both in Nipponbare and Yuexiangzhan after 24 h cultured with 0.5 cm root in 0.5 mmol/L CaCl2 solution with different pH (pH 3.5, 4.5, 5.5, 6.5, 7.5). Root length (RE) was significantly affected by low pH value of the solution (F=70.01,P<0.000 1). The lower the solution pH value was, the shorter the seedling roots would be. In dose-response experiment, Al tolerance of the two cultivars was significantly different (F=25.71, P=0.000 2), Nipponbare showed higher tolerance at various Al concentrations than Yuexiangzhan. 50 μmol/L Al was thought to be the key concentration to discriminate tolerance of rice genotypes to Al stress in simple CaCl2 solutions. In time-course experiment, control root elongation (CRE) and stress root elongation (SRE) all increased along with the culture time prolonged from 6 h to 36 h. But differences of relative root elongation (RRE) between cultivars were significant (F=21.79, P<0.000 1), also in Al stress times (F=5.38,P=0001 3). RRE of Nipponbare was significantly higher than that of Yuexiangzhan. Analysis results of Al content in root tips or apexes were consistent in qualitatively analysis by hematoxylin staining, and quantitatively determination by method of graphite furnace atomic absorption spectrophotometer. There is an increasing trend of Al content in seedling root tips with the increasing of Al concentrations in culture solutions, while more Al was accumulated in seedling root tips of Yuexiangzhan than that in Nipponbare. Based on these results Yuexiangzhan was considered as an Al-sensitive cultivar.

Key words: rice(Oryza sativa L.), aluminum tolerance, seed root formation, relative root elongation

摘要：

我国华南地区土壤为红壤,呈酸性,磷素缺乏和铝毒胁迫共存,是影响该地区水稻产量的重要限制因素。以华南地区主栽水稻品种粤香占及耐铝对照品种日本晴为材料,采用简单钙溶液培养方法,研究了供试材料种子发芽期及幼苗期对酸性条件和铝胁迫的反应,旨在探明粤香占的耐铝性特点。结果表明,在种子萌发过程中,Al显著抑制种子根的形成和生长(F=123.84, P<0.000 1),但粤香占与日本晴种子根形成初期对铝溶液的敏感性差异不显著。培养液梯度pH (pH 3.5, 4.5, 5.5, 65, 75)的实验表明,初生根长05 cm的幼苗在0.5 mmol/L CaCl2的不同pH溶液培养24 h后,幼苗根长的生长量随着溶液pH的降低而显著变短(F=70.01, P<0.000 1)。两个品种的耐铝性对不同Al浓度表现出显著差异(F=25.71, P<0.000 2),日本晴的耐铝性明显优于粤香占。在简单钙溶液培养条件下,50 μmol/L Al浓度可作为不同品种耐铝性的鉴定浓度。在不同Al处理时间的实验中,无Al的对照溶液中的幼苗根伸长量(CRE)和Al处理溶液中的根伸长量 (SRE)都随着培养时间的延长而增长,但是日本晴的相对根伸长量(RRE)显著大于粤香占;且随着培养时间延长,RRE愈小。对根尖铝含量测定结果表明,利用苏木精染色法的定性测定与用原子吸收光谱法的定量测定结果一致,即随着处理溶液中铝浓度的增加,幼苗根尖铝含量随之增多;与日本晴比较而言,粤香占根尖铝积累量更大。上述结果表明粤香占为铝敏感品种。

关键词: 水稻(Oryza sativa L.);耐铝性;种子根的形成;相对根伸长量