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Studies on the Mechanisms of Aluminium Detoxification in Cultivars of Rye

Author: LiYaoYan
Tutor: LiXiaoFeng
School: Guangxi University
Course: Plant Nutrition
Keywords: rye (Secale cereale L.) aluminum resistance organic acid cell wall phosphorus
CLC: S512.5
Type: Master's thesis
Year: 2006
Downloads: 8
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Abstract

Al-induced secretion of organic acids from roots of rye （Secale cereale L.）, which is an aluminum （Al） resistant plant, was shown to be an important mechanism by which Al-resistance in rye was stronger than that in other cereal crops. Nonetheless, the mechanisms of Al detoxification in cultivars of rye are poorly understood. In present study, the difference of Al resistance between two cultivars of rye, King and Wintergrazer-70 （Win）, was investigated. The mechanisms of Al detoxification in terms of the secretion of organic acids from roots under Al stress, the dissolving of sparingly soluble phosphorus by exudates from roots and polysaccharide components of root apex cell wall in cultivars of rye were then investigated. The results are as follows:1. Root elongation of rye seedlings was inhibited significantly after the exposure of roots 1o 10, 30, 50μmol·L^-1 AlCl₃ solution for 24 h and this inhibition was in Al-concentration-dependent manner. The inhibition in Win was much lower than that in King, which indicated that Win was higher resistance to Al than King.2. Al induced a secretion of citric and malic acid from roots of King and Win, and much amount of organic acids was found in the exudates of win after the exposure of roots to 10～50μmol·L^-1 AlCl₃ solution.3. Results of the studies on the secretion of organic acids from roots of Win indicated that the secretion increased with increasing Al concentration (10, 30, 50μmol·L^-1) and periods （0.5, 3, 6, 9, 12 h） of treatment with Al. However, the amount of organic acids was minimal during the first 0.5 h after the treatment with Al (50μmol·L^-1), while the secretion increased significantly from third h of the treatment with Al. On the other hand, both citric acid and malic acid could not be detected in the exudates of roots which were exposed to 10, 50μmol·L^-1La³⁺, 10μmol·L^-1Cu²⁺ or 10μmol·L^-1 Ni²⁺ for 24 h.4. The capacity for neutral component and cation component in the exudates of roots to dissolve sparingly soluble phosphorus was minimal, while anion component released effectively phosphorus into solution from sparingly soluble phosphorus. Furthermore, two cultivars of rye applied with ferric phosphate, aluminum phosphate or calcium phosphate could absorbed effectively phosphorus from sparingly soluble phosphate during 30 d of culture. Finally, Win （Al resistant） showed a stronger capacity than King （Al sensitive） in dissolving sparingly soluble phosphorus by anion components of exudate and in absorbing sparingly soluble phosphorus by plants.5. The amount of cell wall polysaccharide components in the root apex of the cultivars increased after the exposure of roots to 10, 30, 50μmol·L^-1 AlCl₃ solution for 24 h. The increase in pectin and hemicellulose of Win was less than that of King. Though cell wall of roots had a capacity to dissolve sparingly soluble phosphorus, significantly difference in dissolving sparingly soluble phosphorus between two cultivars could not be found.The presented results suggested that the difference in Al-induced secretion of organic acids from roots, cell wall polysaccharide components in root apex and the capacity of root exudates to dissolve sparingly soluble phosphorus involved in Al detoxification difference between cultivars of rye.

Studies on the Mechanisms of Aluminium Detoxification in Cultivars of Rye

Abstract

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