Aluminum （AI） toxicity and phosphorous （P） deficiency are two major limiting factors for plant growth on acidic soils. Thus, the physiological mechanisms for AJ tolerance and P acquisition have been intensively st...Aluminum （AI） toxicity and phosphorous （P） deficiency are two major limiting factors for plant growth on acidic soils. Thus, the physiological mechanisms for AJ tolerance and P acquisition have been intensively studied. A commonly observed trait is that plants have developed the ability to utilize organic acid anions （OAs; mainly malate, citrate and oxalate） to combat AI toxicity and P deficiency. OAs secreted by roots into the rhizosphere can externally chelate Al^3＋ and mobilize phosphate （Pi）, while OAs synthesized in the cell can internally sequester Al^3＋ into the vacuole and release free Pi for metabolism. Molecular mechanisms involved in OA synthesis and transport have been described in detail. Ensuing genetic improvement for AI tolerance and P efficiency through increased OA exudation and/or synthesis in crops has been achieved by transgenic and marker-assisted breeding. This review mainly elucidates the crucial roles of OAs in plant Al tolerance and P efficiency through summarizing associated physiological mechanisms, molecular traits and genetic manipulation of crops.展开更多
Distribution of chemical forms of manganese(Ⅱ)(Mn(Ⅱ))on plant roots may affect Mn(Ⅱ)absorption by plants and toxicity of Mn(Ⅱ)to plants at its high level.The chemical forms of Mn(Ⅱ)on soybean roots were investiga...Distribution of chemical forms of manganese(Ⅱ)(Mn(Ⅱ))on plant roots may affect Mn(Ⅱ)absorption by plants and toxicity of Mn(Ⅱ)to plants at its high level.The chemical forms of Mn(Ⅱ)on soybean roots were investigated to determine the main factors that affect their distribution and relationship with Mn(Ⅱ)plant toxicity.Fresh soybean roots were reacted with Mn(Ⅱ)in solutions,and Mn(Ⅱ)adsorbed on the roots was differentiated into exchangeable,complexed,and precipitated forms through sequential extraction with KNO3,EDTA,and HCl.The exchangeable Mn(Ⅱ)content on the roots was the highest,followed by the complexed and precipitated Mn(Ⅱ)contents.Mn(Ⅱ)toxicity to the roots was greater at pH 5.5 than at pH 4.2 due to the larger amount of exchangeable Mn(Ⅱ)at higher pH.The cations Al3+,La3+,Ca2+,Mg2+,and NH4+competed with Mn(Ⅱ)for cation exchange sites on the root surfaces and thus reduced exchangeable Mn(Ⅱ)on the roots,in the order Al3+,La3+>Ca2+,Mg2+>NH4+.Al3+ and La3+ at 100μmol L-1 decreased exchangeable Mn(Ⅱ)by 80%and 79%,respectively,and Ca2+ and Mg2+at 1 mmol L-1 decreased exchangeable Mn(Ⅱ)by 51%and 73%,respectively.Organic anions oxalate,citrate,and malate reduced free Mn(Ⅱ)concentration in solution through formation of complexes with Mn(Ⅱ),efficiently decreasing exchangeable Mn(Ⅱ)on the roots;the decreases in exchangeable Mn(Ⅱ)on the roots were 30.9%,19.7%,and 10.9%,respectively,which was consistent with the complexing ability of these organic anions with Mn(Ⅱ).Thus,exchangeable Mn(Ⅱ)was the dominant form of Mn(Ⅱ)on the roots and responsible for Mn(Ⅱ)toxicity to plants.The coexisting cations and organic anions reduced the exchangeable Mn(Ⅱ)content,and thus they could alleviate Mn(Ⅱ)toxicity to plants on acid soils.展开更多
The chemical characteristics,element contents,mineral compositions,and the ameliorative effects on acid soils of five biomass ashes from different materials were analyzed. The chemical properties of the ashes varied d...The chemical characteristics,element contents,mineral compositions,and the ameliorative effects on acid soils of five biomass ashes from different materials were analyzed. The chemical properties of the ashes varied depending on the source biomass material. An increase in the concrete shuttering contents in the biomass materials led to higher alkalinity,and higher Ca and Mg levels in biomass ashes,which made them particularly good at ameliorating effects on soil acidity. However,heavy metal contents,such as Cr,Cu,and Zn in the ashes,were relatively high. The incorporation of all ashes increased soil p H,exchangeable base cations,and available phosphorus,but decreased soil exchangeable acidity. The application of the ashes from biomass materials with a high concrete shuttering content increased the soil available heavy metal contents. Therefore,the biomass ashes from wood and crop residues with low concrete contents were the better acid soil amendments.展开更多
基金financially supported by the National Natural Science Foundation of China(No.U1301212)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB15030202)
文摘Aluminum （AI） toxicity and phosphorous （P） deficiency are two major limiting factors for plant growth on acidic soils. Thus, the physiological mechanisms for AJ tolerance and P acquisition have been intensively studied. A commonly observed trait is that plants have developed the ability to utilize organic acid anions （OAs; mainly malate, citrate and oxalate） to combat AI toxicity and P deficiency. OAs secreted by roots into the rhizosphere can externally chelate Al^3＋ and mobilize phosphate （Pi）, while OAs synthesized in the cell can internally sequester Al^3＋ into the vacuole and release free Pi for metabolism. Molecular mechanisms involved in OA synthesis and transport have been described in detail. Ensuing genetic improvement for AI tolerance and P efficiency through increased OA exudation and/or synthesis in crops has been achieved by transgenic and marker-assisted breeding. This review mainly elucidates the crucial roles of OAs in plant Al tolerance and P efficiency through summarizing associated physiological mechanisms, molecular traits and genetic manipulation of crops.
基金supported by the National Natural Science Foundation of China (No. 41230855)
文摘Distribution of chemical forms of manganese(Ⅱ)(Mn(Ⅱ))on plant roots may affect Mn(Ⅱ)absorption by plants and toxicity of Mn(Ⅱ)to plants at its high level.The chemical forms of Mn(Ⅱ)on soybean roots were investigated to determine the main factors that affect their distribution and relationship with Mn(Ⅱ)plant toxicity.Fresh soybean roots were reacted with Mn(Ⅱ)in solutions,and Mn(Ⅱ)adsorbed on the roots was differentiated into exchangeable,complexed,and precipitated forms through sequential extraction with KNO3,EDTA,and HCl.The exchangeable Mn(Ⅱ)content on the roots was the highest,followed by the complexed and precipitated Mn(Ⅱ)contents.Mn(Ⅱ)toxicity to the roots was greater at pH 5.5 than at pH 4.2 due to the larger amount of exchangeable Mn(Ⅱ)at higher pH.The cations Al3+,La3+,Ca2+,Mg2+,and NH4+competed with Mn(Ⅱ)for cation exchange sites on the root surfaces and thus reduced exchangeable Mn(Ⅱ)on the roots,in the order Al3+,La3+>Ca2+,Mg2+>NH4+.Al3+ and La3+ at 100μmol L-1 decreased exchangeable Mn(Ⅱ)by 80%and 79%,respectively,and Ca2+ and Mg2+at 1 mmol L-1 decreased exchangeable Mn(Ⅱ)by 51%and 73%,respectively.Organic anions oxalate,citrate,and malate reduced free Mn(Ⅱ)concentration in solution through formation of complexes with Mn(Ⅱ),efficiently decreasing exchangeable Mn(Ⅱ)on the roots;the decreases in exchangeable Mn(Ⅱ)on the roots were 30.9%,19.7%,and 10.9%,respectively,which was consistent with the complexing ability of these organic anions with Mn(Ⅱ).Thus,exchangeable Mn(Ⅱ)was the dominant form of Mn(Ⅱ)on the roots and responsible for Mn(Ⅱ)toxicity to plants.The coexisting cations and organic anions reduced the exchangeable Mn(Ⅱ)content,and thus they could alleviate Mn(Ⅱ)toxicity to plants on acid soils.
基金supported by the National Key Basic Research Program of China(No.2014CB441003)the National Key Research and Development of China(No.2016YFD0200302)
文摘The chemical characteristics,element contents,mineral compositions,and the ameliorative effects on acid soils of five biomass ashes from different materials were analyzed. The chemical properties of the ashes varied depending on the source biomass material. An increase in the concrete shuttering contents in the biomass materials led to higher alkalinity,and higher Ca and Mg levels in biomass ashes,which made them particularly good at ameliorating effects on soil acidity. However,heavy metal contents,such as Cr,Cu,and Zn in the ashes,were relatively high. The incorporation of all ashes increased soil p H,exchangeable base cations,and available phosphorus,but decreased soil exchangeable acidity. The application of the ashes from biomass materials with a high concrete shuttering content increased the soil available heavy metal contents. Therefore,the biomass ashes from wood and crop residues with low concrete contents were the better acid soil amendments.
