Abstract
摘要：鐵為作物之必需營養元素之一，土壤中鐵的低有效性會限制作物對鐵的吸收，進而影響作物生長。欲提升植物對土壤中鐵的利用效率，必須先了解植物對其吸收之相關機制，其中根分泌物和根圈土壤之交互作用又為控制鐵的植物有效性的主要關鍵。本研究將探討水稻根的分泌物和根圈土壤之交互作用如何決定土壤中鐵的生物有效性，尤其是當水稻感知缺鐵情況時，其根部不同部位的分泌物組成所產生的對應變化，以及後續對土壤根圈中化學物種分布所產生的影響。本研究將探討(1)在鐵缺乏的影響下，水稻根的不同部位之分泌物組成變化，以期鑑定出控制鐵有效性之水稻分泌物、(2)水稻根圈土壤中根圈分泌物組成，以及鐵之物種型態分布隨時間和空間的變化；(3)水稻根分泌物如何影響鐵礦物的生成，以及鐵自相關礦物溶解和脫附的反應機制，藉以說明土壤中相關過程之反應機制。預期本研究之成果，將有助於解釋水稻根分泌物如何決定鐵之根圈化學，水稻根和其根圈環境之交互作用在水稻對土壤鐵的整個吸收過程中所扮演的角色，以及在生物化學基礎上水稻如何透過調控根圈環境來適應缺鐵之營養逆境。
Abstract: Iron (Fe) is an essential microelement for plant growth. The low availability of Fe in soils, mainly resulting from its low solubility and strong retention to soil constituents, can lead to Fe deficiency in plants. Since the release of Fe from soil solids into soil solutions for plant utilization is controlled by the interactions between root exudates and soil constituents, it is critical to understand the interaction mechanisms for enhancing the resistance of plants to Fe deficiency in soils. Accordingly, the goal of this study is to investigate the roles of root exudates in determining the formations and distributions of Fe phases in the rhizosphere of different rice cultivars, the Fe-mobilization efficiency of rice root exudates, and the reaction of rice root exudates to solid phases in paddy soils with an emphasis on the interactive processes between the rice root and rhizosphere soil. There are three lines of attack: (1) to determine the changes in the compositions of the root exudates of paddy rice induced by Fe deficient conditions and identify novel compounds in rice root exudates with specific functions in the selective solubilization and mobilization of Fe; (2) to study the functions of rice root exudates and micro-scale processes in determining the Fe speciation, and the temporal and spatial distributions of root exudations and mineral compositions in the rhizosphere; (3) to investigate the effects of root exudates on the formation of Fe-containing minerals and the reaction rates and mechanisms of rice root exudates with Fe-bearing minerals to clarify functions in regulating Fe solubility in the rice rhizosphere. The results of this proposed research will provide essential information for understanding the interaction and feedback mechanisms between the rice root and rhizosphere soil in controlling Fe availability for rice uptake and bringing insights to rhizosphere biochemical processes controlling the Fe uptake of rice plants.
Keyword(s)
植物營養
鐵缺乏
根分泌物
根圈土壤化學
鐵膜
穩定同位素
X光吸收光譜
Plant nutrition
Iron deficiency
Root exudates
Rhizosphere soil chemistry
Iron plaque
Stable isotope analysis
X-ray absorption spectroscopy
