Apoplastic barriers to radial oxygen loss and solute penetration: a chemical and functional comparison of the exodermis of two wetland species, Phragmites australis and Glyceria maxima

Abstract

Summary• Few studies have examined exodermal development in relation to the formation of barriers to both radial oxygen loss (ROL) and solute penetration along growing roots. Here, we report on the structural development, chemical composition and functional properties of the exodermis in two diverse wetland grasses, Glyceria maxima and Phragmites australis .• Anatomical features, development, the biochemical composition of exodermal suberin and the penetration of apoplastic tracers and oxygen were examined.• Striking interspecific differences in exodermal structure, suberin composition and quantity per unit surface area, and developmental changes along the roots were recorded. Towards the root base, ROL and periodic acid (H 5 IO 6 ) penetration were virtually stopped in P. australis ; in G. maxima , a tight ROL barrier restricted but did not stop H 5 IO 6 penetration and the exodermis failed to stain with lipidic dyes. Cultivation in stagnant deep hypoxia conditions or oxygenated circulating solution affected the longitudinal pattern of ROL profiles in G. maxima but statistically significant changes in exodermal suberin composition or content were not detected.• Interspecific differences in barrier performance were found to be related to hypodermal structure and probably to qualitative as well as quantitative variations in suberin composition and distribution within exodermal cell walls. Implications for root system function are discussed, and it is emphasized that sufficient spatial resolution to identify the effects of developmental changes along roots is crucial for realistic evaluation of exodermal barrier properties.

Morpho-anatomical characterization of root in recurrent selection cycles for flood tolerance of maize (Zea mays L.)

“…Similar barriers were also reported in rice (Colmer 2003a) and grasses (Glyceria maxima and Phragmites australis) (Soukup et al 2007). The presence of a thick barrier in the hypodermis cells of the BR 107 variety as well as of the first selection cycles of cv.…”

Regulation of Root Traits for Internal Aeration and Tolerance to Soil Waterlogging-Flooding Stress

“…High resistance to radial oxygen diffusion may result from suberin in hypodermal/ exodermal cell walls (e.g. in several wetland species; Armstrong et al, 2000;Soukup et al, 2007;Garthwaite et al, 2008;Kotula et al, 2009a). Respiratory activity in the outer cell layers also consumes oxygen (Armstrong, 1979;Armstrong et al, 2000;Garthwaite et al, 2008).…”

Beyond the Barrier: Communication in the Root through the Endodermis

“…Under drought conditions, suberization in the endodermis can be accelerated and may prevent the desiccation of inner tissue layers (Enstone et al, 2002;Henry et al, 2012). Thus, the Casparian strip and suberin lamellae not only prevent uptake of toxic compounds but may also prevent the loss of water under unfavorable environments (Soukup et al, 2007;Baxter et al, 2009;Chen et al, 2011).…”