Acclimation to Soil Flooding–sensing and signal-transduction

Abstract

Flooding results in major changes in the soil environment. The slow diffusion rate of gases in water limits the oxygen supply, which affects aerobic root respiration as well as many (bio)geochemical processes in the soil. Plants from habitats subject to flooding have developed several ways to acclimate to these growth-inhibiting conditions, ranging from pathways that enable anaerobic metabolism to specific morphological and anatomical structures that prevent oxygen shortage. In order to acclimate in a timely manner, it is crucial that a flooding event is accurately sensed by the plant. Sensing may largely occur in two ways: by the decrease of oxygen concentration, and by an increase in ethylene. Although ethylene sensing is now well understood, progress in unraveling the sensing of oxygen has been made only recently. With respect to the signal-transduction pathways, two types of acclimation have received most attention. Aerenchyma formation, to promote gas diffusion through the roots, seems largely under control of ethylene, whereas adventitious root development appears to be induced by an interaction between ethylene and auxin. Parts of these pathways have been described for a range of species, but a complete overview is not yet available. The use of molecular-genetic approaches may fill the gaps in our knowledge, but a lack of suitable model species may hamper further progress.

Ethylene is involved in the complete-submergence induced increase in root iron and manganese plaques in Oryza sativa

“…In addition, we also noticed that CS greatly suppressed rice growth, with fewer and shorter roots than the control (Fig. 1b), which corresponds to previous studies (Visser and Voesenek 2005;Fukao and Bailey-Serres 2008).…”

“…In addition to O 2 and CO 2 , another major gas regulator of rice in submergence responses, ethylene, accumulates continuously leading to a series of changes in plant morphological and anatomical traits (Visser and Voesenek 2005;Fukao and Bailey-Serres 2008). The ethylene concentration in the internodes of excised stem sections increased from 0.02 to 1 lL L -1 after 7 days of partial submergence and was blocked by amiooxyacetic acid or AVG and enhanced by ACC in the Bangladesh variety of floating rice (Métraux and Kende 1983;Raskin and Kende 1984).…”

Comparative spatiotemporal analysis of root aerenchyma formation processes in maize due to sulphate, nitrate or phosphate deprivation

“…Konings and Verschuren (1980) first reported that growth of maize in aerated but N-deficient nutrient solution resulted in the development of aerenchyma in roots. Studies with maize later confirmed that both low concentrations of N or low levels of P nutrition increased aerenchyma formation in roots (Drew et al 1989;Fan et al 2003;Visser and Voesenek 2004). Furthermore, when young maize plants were grown in a complete, well-oxygenated nutrient solution and then deprived of their external source of S, the treatment also induced the formation of aerenchyma in roots (Bouranis et al 2003).…”

“…Aerenchyma is a parenchyma tissue that contains lacunae, created by lysigeny or schizogeny, and is formed during different environmental conditions such as oxygen shortage or deprivation of some nutrients (Drew et al 2000;Visser and Voesenek 2004;Haque et al 2010;Jiang et al 2010;Fagerstedt 2010). It aims to facilitate effective translocation of oxygen, carbon dioxide and ethylene or other gases, to redirect scarce resources or to provide a rapid diffusion path for solutes within the root cortex.…”

“…All these events were completed before cell wall degradation was apparent (Gunawardena et al 2001). Reviews on aerenchyma formation (Evans 2003) and signalling (Xiong and Zhu 2001;Visser and Voesenek 2004) summarize the involvement of various signalling molecules in cell death induced by hypoxia and other stresses.…”