Stem hypertrophic lenticels and secondary aerenchyma enable oxygen transport to roots of soybean in flooded soil

Abstract

Hypertrophic lenticels on the stem of soybean, just above the water surface, are entry points for O(2), and these connect to aerenchyma and enable O(2) transport into roots in flooded soil. Stems that develop aerenchyma thus serve as a 'snorkel' that enables O(2) movement from air to the submerged roots.

Waterproofing Crops: Effective Flooding Survival Strategies

“…For example, in soybean, aerenchyma arises through cell division of the phellogen to form a spongy parenchymaous cell layer between the cortex and epidermis (Thomas et al, 2005;BaileySerres and Voesenek, 2008). This arises after several days of waterlogging and enhances the aeration of roots and nodules necessary for growth and nitrogen fixation, respectively (Shimamura et al, 2010). The single cell layer cortex of Arabidopsis does not form aerenchyma, but waterlogging may promote the formation of lacunae in secondary xylem of the hypocotyl of mature rosettes (Mühlenbock et al, 2007), which could facilitate gas exchange.…”

Anatomical and morphological modifications in response to flooding by six Cerrado tree species

“…Non spaces can form channels that are connected throughout the plant, and serve as routes of low resistance to the diffusion of gases and toxic products derived from the metabolism (Kozlowski 1997;Simone et al 2003;Shimamura et al 2010). Among the six species studied, only T. rosea formed aerenchyma in the roots and stem.…”

“…Secondary aerenchyma in the form of aerenchymatous phellem has been reported in several dicotyledonous wetland species when subjected to flooded conditions (Metcalfe 1931;Jackson 2006). Several lines of evidence show that the presence of these structures can facilitate the entry of oxygen to internal plant tissues (Shimamura et al 2010;Teakle et al 2011). Experiments with soybean (Glycine max) under flooding conditions showed that root growth was inhibited when the entry of atmospheric O 2 to the secondary aerenchyma through hypertrophic lenticels was prevented (Shimamura et al 2003).…”

“…Important structural adaptations that facilitate the diffusion of O 2 include the formation of aerenchyma, adventitious roots, stem hypertrophic lenticels (Justin & Armstrong 1987;Kozlowski 1997;Jackson & Armstrong 1999;Shimamura et al 2010;Somavilla & Graciano-Ribeiro 2012) and stem cracks (Davanso-Fabro et al 1998;Jackson 2006;Medri et al 2011). Reduced growth can be a strategy to conserve energy in order to maintain the metabolism in operating conditions during flooding Batista et al 2008).…”

Effects of Short-Term Waterlogging on Soybean Nodule Nitrogen Fixation at Different Soil Reductions and Temperatures

“…The aerenchyma formed in stem, roots and nodules improves gas exchange between the shoots and root system (Bacanamwo and Purcell, 1999b;Shimamura et al, 2003;Shimamura et al, 2010); the nodule nitrogen fixation is restored by the formed aerenchyma to some extent (Bacanamwo and Purcell, 1999b;Shimamura et al, 2002;Thomas et al, 2005). However, short-term waterlogging for several days (i.e., less than a week) in farm fi elds, did not lead to the development of adventitious roots or the formation of aerenchyma.…”