Drought avoidance is dictated by a collection of traits used to maintain tissue hydration levels and turgidity during water-limited conditions. These traits include deeper and more extensive rooting and the closure of stomata to limit the transpiration of water from leaves. Zoysiagrasses are a group of warm-season turfgrasses, including Zoysia japonica and Zoysia matrella, that are valued for their turfgrass quality; however, they are susceptible to drought relative to other warm-season turfgrass species. The objectives of the study were to determine 1) differences in drought avoidance among a collection of zoysiagrasses and 2) which drought avoidance traits contributed to these differences. Fifteen zoysiagrass genotypes were exposed to either drought or control conditions in a greenhouse environment. Overall performance was assessed by evaluating turfgrass quality and percentage green cover. Drought avoidance was estimated by measuring leaf hydration levels and drought avoidance traits [including stomatal conductance (g S)]; root traits such as total root biomass, specific root length (SRL), and root length density (RLD) were measured. Compared with commercial cultivars Meyer, Palisades, or Zeon, some experimental genotypes maintained greater turfgrass quality during drought, with experimental genotype ‘09-TZ-54-9’ having a quality rating of 7.8 after 20 days of drought compared with 5.3 in ‘Zeon’, 5.2 in ‘Meyer’, and 5.0 in ‘Palisades’. A range of belowground traits such as root biomass was also found to be associated with drought avoidance, with experimental ‘09-TZ-53-20’ having 1.03 total grams, and 2.39 total grams in ‘10-TZ-1254’, compared with 1.14, 1.66, and 3.44 total grams in ‘Meyer’, ‘Zeon’, and ‘Palisades’, respectively. Significant differences in drought avoidance were found among the 15 genotypes, with both belowground rooting traits and aboveground factors affecting transpiration influencing plant performance.
David Jespersen and Brian Schwartz
Bo Xiao and David Jespersen
Turfgrasses have varying tolerance to waterlogging conditions. The objective of this study was to identify important root traits and physiological responses to waterlogging stress in seashore paspalum (Paspalum vaginatum) and bermudagrass (Cynodon sp.). After being exposed to waterlogging conditions for 28 days, turf quality, leaf photosynthesis, transpiration rate, stomatal conductance (g S), and root fresh weight were significantly decreased in bermudagrass, and root lipid peroxidation was significantly increased. However, seashore paspalum was found to be more tolerant to waterlogging conditions and changes in turf quality, photosynthesis, or lipid peroxidation were not seen. The waterlogging treatments increased specific root length (SRL), surface area, and volume and decreased root respiration and diameter to a greater extent in seashore paspalum compared with bermudagrass. Under waterlogging conditions, root aerenchyma formation was found in both seashore paspalum and bermudagrass, but to a greater extent in seashore paspalum. Both grasses exhibited significant increases in root water-soluble carbohydrate (WSC) but to a lesser extent in seashore paspalum than in bermudagrass. Shoot WSC remained unchanged in seashore paspalum but was significantly increased in bermudagrass. These results indicate greater root morphological changes such as root volume, SRL, and root porosity, as well as lower root respiration may be important contributors to waterlogging tolerance for seashore paspalum.