Chloride Uptake and Distribution by Grapevines with Established and Developing Root Systems in Relation to Variations in Rootzone Salinity

Abstract

The purpose of this work was to investigate effects of zonal variations in salinity within the rootzone on chloride uptake and accumulation by grapevines under glasshouse conditions. Rootzone variations in salinity were produced by irrigating sloping sand cultures, held in 60 cm long cylinders, either at the surface or at 20 cm or 40 cm below the surface. Experiments involved vines with either established (roots occupied the length of slopes at day 1 of salt treatment) or developing (roots occupied only top 10 cm of slopes at day 1 of salt treatment) root systems. In all experiments, chloride only accumulated in root tissues which were present or grew into salt affected zones within sand slopes. Salinity (25 mM NaCl) increased petiole chloride concentrations of Sultana vines with established root systems after 28, 56 and 79 days. The magnitude of this increase varied according to the extent of the root system affected by salt. Petiole chloride concentrations were greatest when an entire root system was salt affected and least when only one-fifth was affected. In three experiments involving vines with developing root systems, roots grew into zones which were irrigated with NaCl (50 mM). In two of these experiments, one with Ramsey and the other with Sultana vines, NaCl had no effect on root growth. Root dry weight in the third experiment (comparing Ramsey and Sultana) was significantly reduced by salinity, although the proportions of root systems (based on total dry weight) within the three zones of the root profile were the same as those for control vines. With developing root systems, both Ramsey and Sultana vines accumulated significantly greater chloride concentrations in petioles compared to controls when the entire root system was treated with NaCl (50mM) for 60 days. In two experiments, the first with Ramsey and the second with Sultana vines, chloride did not accumulate in petioles in concentrations significantly greater than corresponding controls when roots grew from non-saline to saline zones. In the third experiment (comparing Ramsey and Sultana vines) chloride accumulated in shoots when roots grew into salt affected zones, but there were no differences, with the exception of proximal and distal petioles, in shoot chloride concentrations between these two cultivars. In all experiments, petiole chloride concentrations within shoots increased basipetally. Results are discussed in relation to assessing variation in chloride accumulation by hybrid grapevines.