【作者】 王国英；

【导师】 张福锁； 李春俭； Fritz Bangerth； Volker R(?)mheld；

【作者基本信息】 中国农业大学 ， 植物营养学， 2005， 博士

【摘要】 顶端优势是高等植物控制地上部分枝的一个重要因素,植株激素在顶端优势中起着重要的作用。本论文以豌豆（Pisum sativum L. cv. Lisa）为主要试验材料,研究缺硼减弱顶端优势和诱导侧芽生长的机理、生长素和细胞分裂素在顶端优势中的重要作用以及两者之间的相互作用。主要结果和结论如下: 1.与对照相比,缺硼降低了豌豆植株顶中生长素和细胞分裂素的浓度、顶中生长素的输出以及节间对生长素的运输能力,导致顶端优势的减弱和侧芽的生长。对缺硼的豌豆植株顶端供硼能够恢复这些过程,且抑制侧芽的生长到对照的水平,表明硼至少影响了生长素和细胞分裂素的合成或代谢过程。与顶端供硼相比,对缺硼的豌豆植株顶端供氮（2-氯-4-吡啶）-氮′-苯基尿素（CPPU,一种人工合成的细胞分裂素）并不能恢复这些过程,从而不能完全抑制侧芽的生长到对照水平,即使对缺硼植株顶端供CPPU和赤霉素也没有抑制侧芽的生长,表明仅仅使用激素如细胞分裂素并不能克服缺硼对顶端优势的影响。 2.对供硼的豌豆植株第2节处供CPPU后明显地促进了侧芽的生长,同时增加了使用位点处生长素的浓度和降低了顶中生长素的输出,导致顶端优势的减弱,这些结果符合生长素的自动抑制假说,即生长素的输出是决定优势芽和休眠芽的主要因素。对缺硼豌豆植株第2节供CPPU行不能维持侧芽持续的生长,且对第2节中生长素的浓度和顶中生长素的输出都没有促进的效果。 3.对缺硼的豌豆植株第2节供硼后增加了顶中生长素的浓度和极性输出,且抑制侧芽的生长到对照水平,这可能是由于使用的硼被运输到顶中从而加强了顶端优势,同时也表明用养分假说并不能完全地解释顶端优势。与此相比,对缺硼的豌豆植株第2节处供硼和CPPU后明显促进了侧芽的生长,说明细胞分裂素对侧芽生长的促进作用只有在供硼的条件下才能表现出来。 4.野生型和突变体番茄分别培养在0、0.5和1μmol·L^-1硼的营养液中。通过分析表明无论是野生型还是突变体,完全缺硼的植株茎对生长素的运输能力要小于供0.5μmol·L^-1和1μmol·L^-1硼的处理。另外,与同等供硼条件下的野生型番茄相比,突变体植株的茎明显降低了对生长素的运输能力。在豌豆上,即使对缺硼植株顶端提供一段时间IAA后,也不能恢复节间对生长素的运输能力。这些结果表明硼直接参与了生长素的极性运输过程。 5.在本试验中,对照豌豆植株去顶后导致地上部细胞分裂素水平的迅速增加和侧芽的生长,而对茎切面供生长素可以抑制细胞分裂素水平的增加和维持顶端优势,表明顶中输出的生长素可能控制根中细胞分裂素的合成。对缺硼的豌豆植株去顶也可以导致细胞分裂素水平的增加,但变化的幅度明显小于对照条件下的变化,表明由于缺硼影响了激素的水平从而减弱了顶端优势。更多还原

【Abstract】 Apical dominance is a common phenomenon in higher plants. Plant hormones play important roles in apical dominance. Boron is one of the essential nutrients for plants and B deficiency induces a series of physiological changes, including the release of lateral bud. In the present study, the mechanism about the B deficiency-induced apical dominance was studied in pea plants （Pisum sativum L. cv. Lisa）. In addition, the roles of auxin and cytokinin in apical dominance were tested under both control and B deficient conditions. Further, the interaction of auxin and cytokinin was investigated with traditional decapitation method. The main results were as followed:1. Compared with the control, B deficiency reduced the auxin and cytokinins concentrations in the shoot apex, indole-3-acetic acid （IAA） export from the shoot apex, and the 3^H-IAA transport capacity in the newly formed internode of pea plants, which resulted in the release of lateral bud growth. Re-supply B to the shoot apex of B deficient pea plants reversed these changes and restored the apical dominance, which suggested that B could affect auxin and cytokinin synthesis or metabolism. On the contrary, re-supply N-（2-chloro-4-pyridyl）-N’-phenylurea （CPPU, a synthetic cytokinin） to the shoot apex of B deficient pea plants had no effect on auxin and cytokinins concentrations, as well as IAA export from the shoot apex, even together with gibberellic acid （GA₃）. As a result, re-supply CPPU could not decrease the lateral bud growth to the control level. These results demonstrated that only CPPU supply could not reverse the apical dominance induced by B deficiency.2. CPPU application to the 2nd node of control plants gradually stimulated the lateral bud growth, manifested by increasing the number, length and fresh weight of the lateral buds. Moreover, CPPU application increased the IAA concentration in the 2nd node, and decreased it in the 2nd internode as well as IAA export from the shoot apex of pea plants, reflecting the release of apical dominance. These processes conformed to the ’auxin autoinhibition theory’, which believes that IAA transport is determinable for dominanted and dominant branches in apical dominance. CPPU application to the 2nd node of B deficient pea plants could not sustain the continuous growth of lateral bud, and had no influence on the IAA concentrations in the 2nd node, 2nd internode and shoot apex, as well as IAA export from the shoot apex.3. Applying B to the 2nd node of B deficient pea plants increased the IAA concentration and export from the shoot apex, and resulted in the establishment of apical dominance. This may imply that most of supplied B had been translocated to the shoot apex, which in turn enhanced the apical dominance. These results also suggested that nutrient supply to the lateral bud alone could not stimulate its growth, that was, ’nutrient hypothesis’ was not enough to explain apical dominance. On the contrary, applying both B and CPPU to the 2^nd node of B deficient pea plants obviously increased the lateral bud growth, which suggested that the stimulatory effect of CPPU on lateral bud growth could occur under enough B supply condition.4. Both wild type and mutant tomato plants were cultivated under 0, 0.5 and 1 μmol·L^-1 B supply,respectively. After 7 days, plants in 0 μmol·L^-1 B supply obviously decreased the 3^H-IAA transport capacity in the stems in both wild type and mutant plants compared with 0.5 and 1 μmol·L^-1 B supplied plants. In addition, the 3^H-IAA transport capacity in mutant plants was always lower than that in wild type at the same B supply level, respectively. In pea plants, even after direct application of IAA to the shoot apex of B deficient plants, 3^H-IAA transport capacity in the internode still could not be restored to the level of control plants. These results showed that B directly involved in the polar auxin transport process.5. Under control condition, decapitation resulted in the rapid increase of cytokinins concentrations in the shoot and the release of lateral bud of pea pl更多还原