Formation and extension of lysigenous aerenchyma in seminal root cortex of spring wheat (Triticum aestivum cv. Bobwhite line SH 98 26) seedlings under different strengths of waterlogging

Abstract

Aerenchyma promotes gas exchange between shoots and roots that supports plant to survive under waterlogged conditions. To understand the process of aerenchyma formation under waterlogged conditions, we developed a method for creating hypoxic pot-culture conditions using different water depths, and used this system to examine the effects of hypoxia on seedling growth and the anatomy of the seminal roots of spring wheat (Triticum aestivum cv. Bobwhite line SH 98 26). After 72 h of waterlogging, the redox potentials of a well-drained control and treatments with a water depth 15 cm below (T-15) and 3 cm above (T+3) the soil surface were +426, +357, and +292 mV, respectively. The root growth of the seedlings was reduced in T+3 plants while the shoot growth did not change significantly during 72 h waterlogging. Root anatomy study showed that wheat formed no aerenchyma under our control condition, but formed aerenchyma in the root cortex in response to hypoxia in T-15 and T+3 conditions. The aerenchyma was initially formed at 2 to 5 cm behind the root tip after 72 h in T-15 and 48 h in T+3. The aerenchyma in T+3 plants then extended by an additional 5 cm towards root base during the next 24 h. Evans blue staining indicated that wheat aerenchyma was lysigenous which resulted from degradation of cortical cells. Thus, the combination of the plant material and the pot-culture method can be used for a basic tool with which to analyse the molecular and physiological mechanisms of lysigenous aerenchyma formation in wheat.