Aerenchyma formation in roots of maize during sulphate starvation

Abstract

Young maize ( Zea mays L., Poaceae) plants were grown in a complete, well-oxygenated nutrient solution and then deprived of their external source of sulphate. This treatment induced the formation of aerenchyma in roots. In addition to the effect of sulphate starvation on root anatomy, the presence and location of superoxide anions and hydrogen peroxide, and changes in calcium and pH were examined. By day 6 of sulphate deprivation, aerenchyma started to form in the roots of plants and the first aerenchymatous spaces were apparent in the middle of the cortex. S-starvation also induced thickening of the cell walls of the endodermis. Active oxygen species appeared in groups of intact mid-cortex cells. Formation of superoxide anion and hydrogen peroxide was found in degenerating cells of the mid-cortex. Very few nuclei in the cortex of S-starved roots fluoresced, being shrunken and near to the cell wall. By day 12 of S-deprivation, a fully developed aerenchyma was apparent and there were only a few 'chains' of cells bridging hypodermis to endodermis and stele of roots. Cell walls of endodermis of S-starved roots increased 68% in thickness. Intensive fluorescence in the cell walls of the endodermal, hypodermal and to a lesser extent of epidermal cells was observed due to the formation of active oxygen species, while there was no fluorescence in the cortical cells. There was a higher Ca concentration in the cells walls of the endodermis and epidermis, compared to the rest of the S-starved root tissues. A higher pH was observed, mainly in the cell walls of the hypodermis and to a lesser extent in the cell walls of the endodermis. Superoxide anion and hydrogen peroxide was found in degenerating cells of the root cortex. There was no fluorescence of nuclei in the cortex of S-starved roots.

Root Cortical Aerenchyma Enhances the Growth of Maize on Soils with Suboptimal Availability of Nitrogen, Phosphorus, and Potassium

“…RCA forms in response to suboptimal availability of nitrogen, phosphorus, sulfur, and water (Konings and Verschuren, 1980;Drew et al, 1989;Bouranis et al, 2003Bouranis et al, , 2006Fan et al, 2003;Zhu et al, 2010). Our simulation results support the hypothesis that RCA formation may substantially benefit plants experiencing deficiencies of nitrogen and phosphorus and suggest that RCA could be beneficial under potassium deficiency as well (Fig.…”

“…We hypothesized that RCA is more beneficial in environments with high nitrate leaching. Sulfur deprivation increases RCA formation Bouranis et al, 2003Bouranis et al, , 2006. Low soil sulfur is usually the result of high sulfate leaching (McGrath and Zhao, 1995).…”

“…Improved oxygen transport is an important function of RCA formation in flooded soils, where low oxygen availability may limit root respiration (Jackson and Armstrong, 1999). However, RCA also forms in response to a variety of other edaphic stresses, including phosphorus, nitrogen, and sulfur deficiency and drought (Konings and Verschuren, 1980;Drew et al, 1989;Bouranis et al, 2003Bouranis et al, , 2006Fan et al, 2003;Zhu et al, 2010). Thus, it has been hypothesized that RCA formation has utility under a variety of edaphic stresses by reducing the metabolic costs of soil exploration (Lynch andBrown, 1998, 2008).…”

Acclimation to Soil Flooding–sensing and signal-transduction

“…Analogously, low phosphorus increased the sensitivity of root elongation in Arabidopsis thaliana to ethylene (Ma et al, 2003). Aerenchyma formation does not appear to be exclusively induced by low phosphorus and nitrogen, since Bouranis et al (2003) found similar responses in sulphate-starved maize plants.…”

The Physiology of Adventitious Roots

“…Catalase then detoxifies hydrogen peroxide, which is involved in both signaling and programmed cell death. Under stress conditions, the amount of reactive oxygen species changes via either increased production of reactive oxygen species or changes in antioxidant levels (Bouranis et al, 2003;Steffens, 2014). In flooded rice plants, ethylene enhances superoxide anion generation by plasma membrane-located NADPH oxidase (Fig.…”