Biological characteristics and the toxicity response to ferrous iron of rice border cells IRON TOXICITY AND STRESS ETHYLENE PRODUCTION IN RICE Effects of exogenous potassium on cell-wall polysaccharide contents of Fe-stressed rice in relation to their iron tolerance Detection and Analysis of QTLs Associated with Resistance to Ferrous Iron Toxicity in Rice ( Oryza sativa L. ),Using Recombinant Inbred Lines