Higher Control of Na+ and Cl− Transport to the Shoot Along With K+/Na+ Selectivity is Determinant for Differential Salt Resistance in Grapevine Rootstocks

In this study, a comparative analysis between two grapevine rootstocks was carried out to characterize their salt sensibility in terms of growth, Na+ and Cl– exclusion from shoots, and K+/Na+ selectivity in the whole plant level associated with photosynthesis efficiency. In the first greenhouse experiment, the ‘IAC 313’ and ‘Paulsen’ grapevine rootstocks were subjected to salinity (80 mM NaCl) for 15 d followed by a salt recovery period (10 d). Later, a second assay was performed using plants incubated in a liquid medium to evaluate the kinetics of root K+ uptake in the absence and presence of NaCl. Salinity affected dry weight (DW) in both rootstocks, but this effect was more severe for ‘Paulsen’ rootstock. Better DW of ‘IAC 313’ under salinity was associated with higher restriction of Na+ and Cl– flux for shoots due to better retention capacity of these ions in roots. In addition, ‘IAC 313’ also showed higher K+/Na+ selectivity in both root uptake and partitioning processes at the whole plant. Under salinity, maximum CO2 assimilation (PNmax), maximum electron transport (Jmax), and Rubisco carboxylation (Vcmax) were also affected more in the ‘Paulsen’ than in ‘IAC 313.’ Our findings show that the characteristic of more favorable ionic homeostasis presented by ‘IAC 313’ rootstock was associated with higher growth, water balance, and carbon assimilation under salinity. In summary, this suggest that the ‘IAC 313’ rootstock is clearly more acclimated to salinity compared to ‘Paulsen’ rootstock.