Understanding the mechanism of ion transport in O2 deficient roots of cereals

KOTULA L.; STRIKER GG; PEDERSEN O; CLODE PL; LÄUCHLI A; COLMER TD

Perth

Congreso; ComBio2013; 2013

Australian Society of Plant Scientists

O2 deficiency during soil waterlogging adversely affects root growth and functioning, with subsequent consequences for shoots. For roots in O2 deficient media, large gradients in O2 occur across root tissues. Hypoxia or even anoxia can develop in the stele, while the cortex and epidermis receive sufficient O2 for respiration. O2 deficiency in stellar cells causes energy deficits, as a result the activity of H+-ATPases is restricted by low ATP. The present study aims to elucidate the relationship between root O2 supply and ion transport in roots affected by hypoxia, and the combination of hypoxia and salinity. Two species, barley and wheat, which differ in their tolerance to waterlogging and salinity were used. O2 status of roots was determined on plants grown in stagnant and stagnant+saline conditions and compared with plants grown in aerated and aerated+saline conditions. The O2 microelectrode profiles showed that for roots in stagnant conditions, O2 deficiency first occurs in the stele whereas at the same time the cortex can contain some O2. This condition was more severe towards the root apex. Measurements of Na+, K+ and Cl- across adventitious roots (epidermis, cortex, xylem parenchyma, and xylem) from aerated, aerated+saline, stagnant, and stagnant+saline treatments were determined using quantitative X-ray microanalysis of freeze-substituted material. These measurements showed that K+ concentration in xylem parenchyma cells was lower in O2 deficient roots, whereas the Na+ concentration in these roots was higher. Moreover, cells of roots subjected to salt stress produced Na+-binding starch granules.