Effects of aluminium on root growth and apical root cells in rice (Oryza sativa L.) cultivars. Reliability of screening tests to detect Al resistance at the seedling stage

The effects of Al₂(SO₄)₃·18H₂O on growth of root and apical root cells were studied in seedlings of rice cultivars differing in Al resistance including I Kong Pao and Aiwu (Al-sensitive) and IRAT 112 and IR6023-10-1-1 (Al-resistant). Inhibition of root growth was a typical effect of Al, and the extent of the inhibition depended on both cultivar and Al concentration. Al impaired the activity of the root meristem as indicated by reductions in its size, mitotic activity and the diameter of the meristematic cell nucleoli. Cell size in the elongation zone of the root was also reduced by Al. The reliability of the haematoxylin staining method to classify rice cultivars according to their Al-sensitivity failed to discriminate the Al-resistant IR6023-10-1-1 cultivar from the two sensitive cultivars. The results are discussed in relation to the Al resistance mechanisms operating in rice.