Growth and physiological traits of canopy and root systems associated with drought resistance in Tall fescue

Water uptake and usage are important factors affecting plant adaption to drought stress. The objective of this study was to determine morphological and physiological traits of the grass canopy and root systems governing plant water relations in association with genetic variability in tall fescue (Festuca arundinacea Schreb.) drought resistance. Grass canopy and root traits (turf quality [TQ], relative water content [rWC], evapotranspiration [ET] rate, single-leaf net photosynthesis rate [pn], stomatal conductance [gs], stomatal aperture [SA] and density, transpiration rate [Tr], root length [rL], root dry weight [rDW], root viability or root electrolyte leakage [rEL], and specific root length [SrL]) were examined in seven tall fescue genotypes during drought stress in two repeated trials of a controlled-environment growth chamber study (May-June and September-october 2011). All these canopy and root traits exhibited significant variability in drought responses among tall fescue genotypes while pn, gs, Tr, rL, rDW, and SrL also varied among genotypes under well-watered conditions. Correlation and principal component analysis of traits associated with genetic variability in drought resistance demonstrated that the superior turf performance (higher TQ) and leaf hydration status (higher rWC) under drought stress were associated with sustained stomatal opening (greater SA and gs) and water use rate (higher Tr and ET), maintaining higher pn as well as the development of the root system with higher viability (lower rEL) and finer diameter (higher SrL). Integration of canopy and root traits controlling both water consumption and water uptake will facilitate breeding improvement of drought resistance in tall fescue and other cool-season grass species.