Aluminium-induced changes in the surface and micropore properties of wheatroots: a study using the water vapor adsorption-desorption technique

The geometric and energetic characteristics of root surfaces of two wheat ( Triticum L.) varieties, Al tolerant ( Inia 66/16) and Al sensitive ( Henik a), were estimated from experimental water vapor adsorption-desorption data . Roots stressed for around 1 week at pH 4 without and with a toxic alumini um level (0.741 mol m(-3)) were studied at the tillering and shooting stage s. Roots grown continuously at pH 7 were taken as control. The surface prop erties of the pH 4 stressed roots were apparently the same as those of the control roots whatever the root age. For the roots of both varieties, the s urface area and total micropore volume increased markedly after aluminium t reatment. The average micropore radius increased significantly for the sens itive wheat, whereas it increased only slightly for the resistant one. Unde r Al treatment the number of large pores increased while small pores were f ewer for both plants, indicating a possible alteration of the build-up of r oot tissue. The root surface pores were fractal. The fractal dimension of t he sensitive wheat roots decreased under Al treatment, whereas for the resi stant wheat this remained apparently unchanged. The adsorption energy distr ibution functions had different shapes for the sensitive and the resistant wheat varieties: the sensitive variety had greater number of high energy ad sorption centers, which implies that the root tolerance on Al stress may be connected with lower polarity of the surface.