The radial oxygen loss in Typha domingensis as related to aerenchyma, gas diffusion and catalase activity

Abstract

Radial oxygen loss (ROL) is a physical phenomenon that occurs naturally in plants, mostly those live in wetlands or flooded environments. Although this phenomenon is present in almost all macrophytes, ROL can vary among these species. Typha domingensis PERS. was used as a model plant because it presents basic morphological characteristics found in most aquatic plants such as leaves emerging from a stem (rhizome) and from it adventitious roots. This work aimed to investigate: the anatomy of T. domingensis on gas diffusion between different organs; the influence of plant parts on ROL and the catalase role in ROL, besides providing a model as an alternative way to explain the downward diffusion of oxygen between the plant and the environment in which it is inserted. The plants of T. domingensis were cultivated in Hoagland solution in greenhouse under different conditions: Plants with intact leaves, plants with leaves cut in half and plants without leaves. The percentage of aerenchyma in the different vegetative organs, the minimum pressure required for ROL, the daily variations of dissolved oxygen and the catalase (CAT) activity enzyme in the roots were evaluated. The results demonstrated that the cellular traits in the leaf-rhizome connection and the root-rhizome interface besides suberin/lignin layer in these regions contribute to the decrease of the oxygen diffusion of between the organs. The results with the CAT activator and inhibitor also contributed to prove that a significant amount of the oxygen released into the roots by ROL can not, in fact, to be only supplied by the atmosphere, as suggested by the theories.