Aluminum-induced ultraweak luminescence changes and sister-chromatid exchanges in root tip cells of barley

Abstract

Ultraweak luminescence (UL) changes and sister-chromatid exchanges (SCEs) induced by Al toxicity were investigated in root tip cells of barley ( Hordeum vulgare L.). A low positive correlation between relative UL rates and root relative elongation rates (RERs) was observed in 30 barley cultivars. During 1.5–24 h exposure to 20 μM Al solution, the UL value in cv Humai 16 (Al-tolerant) was higher than that in cv 2000-2 (Al-sensitive), suggesting that UL is a possible mechanism by which Al-tolerant cultivars avoid reactive oxygen species (ROS) toxicity. Upon raising Al levels (>50 μM), the increase for UL in Al-tolerant and sensitive cultivars possibly involved cell death. A significant increase in the SCE rate was observed in cv 2000-2 but not in cv Humai 16 at 20 μM Al level, suggesting that mechanisms of Al-tolerance might block the occurrence of Al-induced SCEs. With raising Al levels (0–640 μM), SCE rates first increased and then decreased in the two cultivars, but their Al levels inducing the highest SCE rate were 10 μM in cv 2000-2 and 320 μM in cv Humai 16. In cv 2000-2, SCEs reached saturation status after 4 h treatment with 10 μM Al, suggesting that SCEs can be considered as a sensitive indicator for Al phytotoxicity. Ascorbic acid (ASA) pretreatment could significantly inhibit Al-induced SCE occurrence, indicating that Al indirectly induces SCEs via Al-triggered ROS formation. To our knowledge, this is the first report demonstrating that Al can induce UL changes and SCEs in root tip cells, and that may serve as possible indicators and thereby provide new insights into the mechanisms of Al toxicity and tolerance in barley.