Anatomical Changes of Grapevine (Vitis vinifera L. Cv. Shiraz) Roots Related to Radial Resistance to Water Movement

The anatomical features of grapevine roots that are postulated to influence radial resistance to water movement through plants were studied using roots of pot-grown 212-day-old and young roots of 20-year-old field grown grapevines. The number and percentage of cells and the percentage of surface area of the endodermis suberised rose with distance from the root tip. There were no significant differences between the extent of suberisation of well-watered and stressed plants. There was a significant negative relationship between the proportion of the root occupied by the cortex and distance from the tip, but the regression coefficient for non-irrigated plants was more negative than that of irrigated plants suggesting greater cortical breakdown in non-irrigated than irrigated root segments at equal distance from the tip. Cortical resistance is likely to be the major component of radial resistance to water through apical regions of the root while endodermal resistance and resistance offered by the peripheral vascular parenchyma are likely to become the dominant components of radial resistance in basal regions of the root. In large and older roots of grapevine the cortex is completely destroyed and cortical resistance becomes negligible.