Root Respiration and Carbohydrate Status of Two Wheat Genotypes in Response to Hypoxia

Abstract

To investigate root respiration and carbohydrate status in relation to waterlogging or hypoxia tolerance, root respiration rate and concentrations of soluble sugars in leaves and roots were determined for two wheat ( Triticum aestivum L.) genotypes differing in waterlogging-tolerance under hypoxia (5% O 2) and subsequent resumption of full aeration. Root and shoot growth were reduced by hypoxia to a larger extent for waterlogging-sensitive Coker 9835. Root respiration or oxygen consumption rate declined with hypoxia, but recovered after 7 d of resumption of aeration. Respiration rate was greater for sensitive Coker 9835 than for tolerant Jackson within 8 d after hypoxia. The concentrations of sucrose, glucose and fructose decreased in leaves for both genotypes under hypoxia. The concentration of these sugars in roots, however, increased under hypoxia, to a greater degree for Jackson. An increase in the ratio of root sugar concentration to shoot sugar concentration was found for Jackson under hypoxic conditions, suggesting that a large amount of carbohydrate was partitioned to roots under hypoxia. The results indicated that root carbohydrate supply was not a limiting factor for root growth and respiration under hypoxia. Plant tolerance to waterlogging of hypoxia appeared to be associated with low root respiration or oxygen consumption rate and high sugar accumulation under hypoxic conditions.