Growth and water relation responses to salinity stress in halophytic seashore paspalum ecotypes

This study was to assess selection criteria for salt tolerance in halophytic seashore paspalum (Paspalum vaginatum Swartz) ecotypes, and to determine influence of salinity on water status. Nine seashore paspalums exhibiting the widest range of salinity tolerance were grown in a greenhouse using nutrient/sand culture. Comparative salinity tolerance was determined by measuring shoot, root, and verdure dry weights at six salinity levels (1.2-49.7 dS m−1). Threshold ECw (electrical conductivity of water), ECw50%, ECw25%, and leaf firing (LF50) were also measured. Total water potential (Ψw), solute potential (Ψs), turgor pressure (Ψp), and relative water content (RWC) were determined as measures of water status across salinity levels. Based on the number of times in the top (best) statistical category for growth measurements, SI 93-2 and HI 101 were the most salt-tolerant ecotypes, while Adalayd was least tolerant. Results indicated that comprehensive assessment of salt tolerance using different tissues across salinity levels up to ECw50 were desirable and repeatable in halophytic seashore paspalums. The criteria ECw50%, ECw25%, and LF50 were also useful in ranking of salt tolerance, but threshold ECw was not reliable in halophytic turfgrass. Shoot Ψw and Ψs decreased continuously in all ecotypes as salinity increased. Trends in shoot growth of salt-tolerant SI 93-2 and HI 101 and least tolerant Adalayd paralleled responses of shoot Ψp with the more tolerant ecotypes maintaining more favorable Ψp and growth. Among parameters of water relations, shoot Ψw and Ψp were found to have the largest effects, which accounted for 82% and 22% of variations of shoot and root growth of seashore paspalums, respectively.