Cl^- uptake, transport and accumulation in grapevine rootstocks of differing capacity for Cl^--exclusion

Mechanisms of chloride (Cl^-) exclusion in rootstocks of grapevine (Vitis spp.) were studied using a strong Cl^--excluding rootstock (140 Ruggeri) and a poor Cl^--excluding rootstock (K51-40). Xylem Cl^- concentration in potted whole grapevines of 140 Ruggeri treated with 50mM Cl^- was 6.8-fold lower than that in K5140. Five-fold lower total shoot Cl^- in salt-treated 140 Ruggeri grapevines relative to that in K51-40 after 50 days, when shoots were of similar biomass, was unrelated to water use. Unidirectional influx of ³⁶Cl^- into excised roots (up to 30min), and uptake of ³⁶Cl^- in roots of intact rooted-leaves (up to 180min) in 10mM Cl^- was similar between the genotypes. However, net accumulation of Cl^- by excised roots of K51-40 up to 180min in 10mM Cl ^- was significantly higher than that of 140 Ruggeri. Intact rooted-leaves of 140 Ruggeri in 10mM Cl^- accumulated higher Cl ^- concentrations in roots, and had a lower percentage of total plant ³⁶Cl^- accumulation in the shoot (petiole plus lamina) than those of K51-40. The greater Cl^- exclusion capacity of 140 Ruggeri appears to be associated with restricted entry of Cl^- to xylem and lower root to shoot Cl^- transport.