Accumulation of potassium in grapevine rootstocks (Vitis) grafted to 'Shiraz' as affected by growth, root-traits and transpiration

The concentration of potassium (K) in scions call be controlled by rootstocks (Vitis). However, differences between rootstocks in the accumulation of K and mechanisms of regulation of K, when rootstocks are grafted to a scion, are not clearly understood. Therefore, the current study addresses these issues. Rootstocks Freedom, Schwarzmann, Ramsey, 1103 Paulsen, 110 Richter, 140 Ruggeri and 101-14 were grafted with 'Shiraz' and grown in sand for 56 days in a glasshouse, with daily watering using solutions containing 3 mM K. At day 56, Freedom had highest total K uptake. Freedom and 101-14 had the highest and 140 Ruggeri the lowest concentration of K respectively, in shoot and roots. Accumulation of K in grapevine is affected by the interaction between rootstock and scion, with total K uptake increasing with total root length, total root surface area and percentage of roots ill small diameter class (<0.5 mm). Accumulation of K in the whole grapevine or in the shoot was not affected by either shoot/roots dry weight or transpiration, but was positively related to concentration of K (but not Na) in xylem. The current study highlights the positive impact of root based factors, specifically root traits and root pressure than other (e.g. shoot/roots dry weight, transpiration) ill the accumulation of K in 'Shiraz' grapevines when assessed as grafted vines oil a range of rootstocks. This knowledge will be important in selecting the new rootstocks for appropriate K uptake or accumulation.