Aluminum-induced hydroxamic acid secretion in maize roots and its response to light conditions and ferrum element

【Objective】To explore the effect and correlation of hydroxamic acid secretion in maize roots and hydroxamic acid content in maize plants under aluminum(Al) stress,and analyze the response of the hydroxamic acid secretion in maize roots under Al stress to environmental conditionslight conditions and ferrum(Fe) element,providing theoretical basis for the mechanism of Al tolerance in maize.【Method】A hydroponic experiment was conducted,in which Taiyu 11(Al tolerant variety) and Zhengdan 958(Al sensitive variety) were experimental materials that were treated with0µmol/L(control) and 20µmol/L AlCl₃.After 3,6,9,12 and 24 h,the hydroxamic acid secretion in maize roots and its content in maize plants were measured to analyze the correlation between the two.The light conditions were set as natural light(14 h of light exposure/10 h of darkness) and darkness(24 h),and Fe³⁺concentrations were 0,5,10 and 20µmol/L.After 24 h of treatment with 0 and 10µmol/L AlCl₃,the amount of hydroxamic acid secretion in maize roots was measured to analyze the effects of light conditions and Fe element on the secretion under Al stress.【Result】With the extension of Al stress time,the hydroxamic acid secretion in the root of Taiyu 11 showed an increasing trend,and after 9 h under Al stress,it began to be significantly higher than that of the control(p<0.05,the same below);whereas,in each time period under Al stress,there was no significant difference between Zhengdan 958 and the control(P<0.05,the same below) and the secretion of Taiyu 11 was significantly higher than that of Zhengdan 958.Taiyu 11 had a long secretion duration and a large amount of secretion,while Zhengdan 958 did not respond obviously to either Al stress or the length of Al stress time.Hydroxamic acid secretion in maize roots was closely related to the hydroxamic acid content in maize plants under Al stress,and the secretion of Taiyu 11 showed a significant or extremely significant positive correlation with the hydroxamic acid content in the roots and leaves(P<0.01,the same below).However,the secretion of Zhengdan 958 had no significant correlation with the hydroxamic acid content in the roots,but a significant or extremely significant negative correlation with hydroxamic acid content in the leaves.The rise of Al-induced secretion in the roots synchronized with the rise of hydroxamic acid content in the roots and leaves.The hydroxamic acid secretion in maize roots under Al stress significantly increased in dark.The hydroxamic acid secretion in maize roots under Al stress tended to increase with the rise of Fe concentration,and reached the highest value at the concentration of more than 20µmol/L.【Conclusion】The hydroxamic acid secretion induced by Al in Taiyu 11,an Al tolerant maize variety,may be related to the anabolism of hydroxamic acid in the plants.Al may regulate the anabolism and secretion of hydroxamic acid,and environmental conditions(light conditions and Fe element) significantly affect the amount of Al-induced hydroxamic acid secretion in maize roots.