【作者】 李枝；

【导师】 王昌全；

【作者基本信息】 四川农业大学 ， 土壤学， 2009， 硕士

【摘要】 近年来,由于工业废物处理不善以及含有镉(Cd)的农药、化肥的不合理使用,我国稻田Cd污染现象日益严重,不仅影响水稻的生长发育,降低产量与品质,而且对人体健康产生了巨大威胁。目前,从Cd的化学结合形态和亚细胞分布角度探讨杂交水稻对Cd的耐性机理的研究鲜见报道。本文通过水培试验,以籽粒Cd积累量不同的4个杂交水稻品种为材料,研究了Cd在杂交水稻不同部位的化学结合形态、亚细胞分布情况以及Cd胁迫对杂交水稻体内抗坏血酸和可溶性糖含量的影响,进一步揭示了杂交水稻籽粒低量积累Cd的耐性机制。主要研究结果如下:(1)不同浓度Cd胁迫下,D83A/R527籽粒的Cd含量显著低于辐优838、D优498、Ⅱ优892;4个品种的Cd含量在1mg/LCd处理与0.5mg/LCd处理时相比,D83A/R527的增幅较小;3mg/LCd处理与1mg/LCd处理时相比,虽然D83A/R527的增幅较Ⅱ优892高出16%,但其Cd含量依然最低。说明D83A/R527属于籽粒低镉积累品种。(2)随着Cd胁迫水平的提高,根、根颈、茎、叶鞘、叶和穗颈的总Cd含量和不同化学形态Cd含量均增加。不同部位的Cd积累量不同,总体上表现为根＞根颈＞茎＞叶鞘＞叶片＞穗颈;根、根颈、叶鞘、叶和穗颈中,氯化钠提取态和醋酸提取态是优势形态,但在茎中,乙醇提取态的比例较高,仅次于氯化钠提取态;茎部乙醇加水提取态的比例较高,其次是叶鞘、叶片、穗颈,根和根颈乙醇加水提取态的比例较低,证明不同部位Cd积累量的差异可能与Cd在其中的化学形态差异有关。4个品种相比较,D83A/R527各部位总Cd含量和不同化学形态Cd含量最低;乙醇加水提取态的比例最低,而醋酸加盐酸提取态的比例最高,说明其体内的Cd处于难以移动的状态,导致其籽粒中Cd积累量较低。(3)根颈、叶鞘、穗颈各亚细胞组分中的Cd含量随Cd处理浓度的增加而增加。Cd在各亚细胞组分中的分配比例,除分蘖期根颈可溶性部分大于细胞壁外,整体上表现为细胞壁＞可溶性部分＞细胞器。根颈的Cd含量显著大于叶鞘和穗颈;Cd在根颈细胞壁中的分配比例小于叶鞘和穗颈,可溶性部分的分配比例大于叶鞘和穗颈,说明不同部位Cd含量的差异可能与Cd在其中的亚细胞分布有关。D83A/R527各亚细胞组分中的Cd含量整体上较低,其次是D优498和Ⅱ优892,辐优838各组分中的Cd含量较高;Cd在D83A/R527细胞壁中的分配比例高于其他品种,可溶性部分和细胞器部分中的比例较低,降低了Cd在其体内的迁移,致使其籽粒中Cd含量较低。(4)0.5mg/LCd胁迫有利于提高分蘖期和孕穗期水稻叶片的抗坏血酸含量,而1mg/L和3mg/LCd胁迫对分蘖期和孕穗期叶片抗坏血酸含量有抑制作用,Cd处理显著降低了灌浆期叶片的抗坏血酸含量;任何浓度的Cd胁迫,均显著降低了茎部的抗坏血酸含量。低镉积累品种D83A/R527的茎叶中一直保持较高的抗坏血酸含量,变化幅度小,其次是D优498和Ⅱ优892,辐优838的抗坏血酸含量较低,变化幅度大。抗坏血酸的含量与不同化学形态Cd含量及总Cd含量均达极显著负相关关系,说明各种化学形态Cd含量均对抗坏血酸含量的变化产生了显著影响,水稻抗坏血酸含量的高低可以反映出抗Cd能力的高低。(5)在不同浓度的Cd胁迫下,水稻茎叶的可溶性糖含量较对照均显著提高,且随着Cd处理浓度的提高,可溶性糖含量不断上升。与3个籽粒高镉积累品种相比,低镉积累品种D83A/R527茎叶的可溶性糖含量较低,且始终保持较低的可溶性糖累积速度。可溶性糖的含量与不同化学形态Cd含量及总Cd含量均达显著性正相关关系,进一步证实可溶性糖发挥了在逆境胁迫中的信号作用。更多还原

【Abstract】 In recent years, industrial waste hasn’t been dealt properly, and pesticide and chemical fertilizer （Cd included） have been used unreasonably. Owing to that, a great deal of paddy soil has been contaminated by Cadmium, not only the growth and development of rice were inhibited, yield and quality were reduced, but also human health was threatened greatly. At present, the study about the mechanism of hybrid rice under Cd stress from the viewpoint of chemical forms and subcellular distribution have been reported seldom. Taking one hybrid rice cultivar with low Cd accumulated in grain and three hybrid rice cultivars with high Cd accumulated in grain as study materials, a hydroponic experiment was carried out to study the chemical forms and subcellular distribution of Cd and the effect of Cd on Ascorbate acid and soluble sugar in different organs of hybrid rice, and further to reveal the tolerance mechanism of hybrid rice under Cd stress. The main results are as follows:（1） The Cd content in grain of D83A/R527 was lower than FuYou838、D You498、II You892 under Cd stress. Compared with the treatment of 0.5mg/LCd, the amplification of Cd content in grain of D83A/R527 in the four varieties was the smallest under the treatment of 1mg/LCd. And contrasted the content under the treatment of 3mg/L and 1mg/LCd, although the amplification of D83A/R527 was higher than II You892 by 16%, the content in grain of D83A/R527 was also the lowest. It showed there was low Cd accumulated in grain of D83A/R527.（2） In root, crown, stem, leaf sheath, leaf and uppermost internode of four hybrid rice cultivars, increased Cd level in the medium caused a significant increase of Cd concentration in total Cd content and chemical forms. The contents of Cd were different in each organ, and on the whole, and the order was: root>crown>stem>leaf sheath>leaf> uppermost internode. In root, crown, leaf sheath, leaf and uppermost internode, the greatest amount of Cd was found in extraction solution of NaCl, followed by HAC. But in stem, the extraction of ethanol was higher than HAC. The proportion of ethanol and H₂O extractable-Cd in stem was the highest, then were leaf sheath, leaf, uppermost internode, and next were root and crown, it proved the different Cd content in every organ was in correlation with the difference of chemical forms. Compared with other three cultivars with high Cd accumulated in grain, total Cd content and each extractable-Cd content of D83A/R527 were lower, and it was lower in proportion of H₂O and ethanol extractable-Cd, but higher in proportion of HAC and HCl extractable-Cd. It suggested that Cd in D83A/R527 was hard to mobile, and leaded to low accumulation of Cd in grain.（3 ） In crown, leaf sheath and uppermost internode of four cultivars, increased Cd level in the medium caused a significant increase of Cd concentration in all fractions and total Cd content. Most Cd was distributed in F₁（cell wall fraction）, followed by F3（soluble fraction） and F2（organelle fraction） except in crown in Tillering stage, F₃>F₁. The subcellular distribution of Cd in different organs was different, on the whole, the Cd content of crown was higher than leaf sheath and uppermost internode, and the proportion in cell wall of crown was lower than leaf sheath and uppermost internode, but the proportion in soluble fraction was higher, it revealed the difference of Cd content in each organ was in correlation with the difference of subcellular distribution. The Cd content in all fractions and total Cd content of D83A/R527 was the lowest, then were D You498 and II You892, FuYou838 was the highest. And D83A/R527 had higher Cd proportion in the cell wall but lower in the soluble fraction and organelle fraction, this was the mechanism of D83A/R527 low accumulation of Cd in grain.（4） Ascorbate acid content of leaf in tillering and booting stage increased when the four hybrid rice cultivars subjected to 0.5mg/LCd stress, but it was inhibited when subjected to 1mg/L and 3mg/LCd stress. However, in filling stage, ascorbate acid content of leaf decreased significantly under Cd stress. And ascorbate acid content of stem decreased significantly under Cd stress in the three growth stages. Compared with other three cultivars with higher Cd accumulated in grain, D83A/R527 had higer ascorbate acid content and the rangeability was small. There were significant and negative correlation between Ascorbate acid content and each extractable-Cd content and also the total Cd content, the results indicated the influence of the extractable-Cd content on ascorbate acid content was significant.（5） Compared with the contrast, Soluble sugar content of leaf and stem in hybrid rice increased significantly and showed rising trend with the increase of Cd concentrations. Compared with the other three cultivars with high Cd accumulated in grain, D83A/R527 had lower soluble sugar content and accumulating speed. There were significant and positive correlation between soluble sugar content and each extractable-Cd content and total Cd content, and the results further showed the effecct of the extractable-Cd content on soluble sugar content was significant.更多还原