Root and Shoot Growth of Wheat Genotypes in Response to Hypoxia and Subsequent Resumption of Aeration

Abstract

Understanding plant responses to hypoxiand subsequent resumption of aeration is important for breeding tolerant genotypes. The growth response of six wheat genotypes (Triticum aestivum L.) to hypoxiand subsequent recovery was evaluated. Plants were grown for 14 and 21 d in nutrient solutions flushed with air (aerated control) or with a mixture of 02 and N2 (hypoxia) or hypoxia for 14 d followed by aeration for 7 d (recovery). Shoot and root growth was inhibited by hypoxia, with roots being more sensitive. Stomatal conductance (gs) was reduced beginning 5 to 7 d after hypoxia. The adverse effect of hypoxia was most severe for Bayles and FL302, intermediate for BR34 and Coker‐9766, and least for Gore and Savannah. Hypoxia enhanced formation of aerenchyma in roots, to a greater extent for Gore and Savannah. Aerenchyma became more conspicuous with duration of hypoxia. Seven days after resumption of aeration, shoot growth recovered completely for Gore and Savannah but only partially for Bayles, FL302, BR34, and Coker‐9766. The number and length of crown roots increased to the value of the controls for all genotypes, whereas seminal root length was restored only in Bayles, Gore, and Savannah. Stomatal conductance recovered within 5 d for Savannah and 10 d for Gore but never recovered for Bayles, FL302, BR34, and Coker‐9766. Breeding for hypoxia tolerance could be facilitated by selecting genotypes that develop more crown roots and more aerenchyma in those roots, maintain stomatal opening under hypoxic conditions, and resume seminal root growth and opening of stomatafter termination of hypoxia.