Genotypic Difference in Aluminum Resistance and Oxalate Exudation of Buckwheat

Abstract

Genotypic difference in aluminum (Al) resistance of buckwheat (Fagopyrum esculentum Moench.) was first tested using a simple salt solution (0.5 mM CaCl₂) containing 25 µM AlCl₃. Two contrasting genotypes, resistant 92‐1 vs. sensitive Liangqiao 1, were selected out of five, and further tested by a long‐term Al treatment in 1/5 strength of Hoagland solution. Consistent results were obtained by the two methods although much higher Al³⁺ concentration was needed to cause the genotypic difference in the culture solution (up to 2000 µM compared with 25 µM Al³⁺ in simple salt solution). Oxalate content and exudation was decreased when the plants were subjected to the long‐term Al treatment of both genotypes, 92‐1, however, excreted more oxalate than Liangqiao 1 either in Al‐treated or non‐treated plants. If the plants were treated with 100 µM Al³⁺ in 0.5 mM CaCl₂ solution for 24 h, oxalate exudation was very significantly induced: 4‐fold increase for 92‐1 and 1‐fold increase for Liangqiao 1. This supports the previous report that Al‐induced oxalate exudation is a rapid response and may not last a long time. It is, therefore, suggested that the constitutive excreted and internal oxalate may be able to contribute more than the induced oxalate in copying with Al toxicity as well as conferring the genotypic difference especially when the stress is strong and lasting.

Acknowledgment

This work was supported by the National Natural Science Foundation of China (NSFC 30070453) and the Provincial Natural Science Foundation of Guandong (PSFG 980163).