Osmotic Adjustment and Root Growth Associated with Drought Preconditioning‐Enhanced Heat Tolerance in Kentucky Bluegrass

Abstract

Prior exposure to drought stress (drought preconditioning) affects turfgrass tolerance to subsequent heat stress. The study was designed to examine whether these effects for Kentucky bluegrass (Poa pratensis L.) are associated with osmotic adjustment and root growth. Plants were subjected to two cycles of drying and rewatering, and turf quality was then allowed to recover to the well watered control level before being exposed to 21 d of heat stress (35°C/30°C) in growth chambers. Compared with nonpreconditioned plants, drought‐preconditioned plants had 13 and 21% higher turf quality, 6 and 10% higher leaf relative water content, and 17 and 48% higher osmotic adjustment at 14 and 21 d of heat stress, respectively. Total ion (K+, Ca2+, Na+, Ma2+, Cl−, and P) concentration of cell sap increased during heat stress and was 11 to 16% higher in drought‐preconditioned plants than nonpreconditioned plants. The concentration of K+ accounted for 59 to 65% of total ion solutes in both groups of plants during heat stress. Soluble carbohydrate content (WSC) of leaves increased during heat stress and was about 21 and 44% higher in drought‐preconditioned plants than nonpreconditioned plants at 14 and 21 d, respectively. Heat stress decreased root dry weight (DW) and WSC, but significant higher DW and WSC content of roots in the 40–60 cm soil layer were observed for preconditioned plants than nonpreconditioned plants before and after heat stress. The results demonstrated that drought preconditioning enhanced heat tolerance in Kentucky bluegrass, which could be related to the maintenance of higher osmotic adjustment associated with accumulation of ion solutes and water soluble carbohydrates and development of extensive roots deeper in the soil profile.

Leaf-Water Relations of a Native and an Introduced Grass Species in the Mixed-Grass Prairie Under Cattle Grazing

“…Poa, an introduced grass responding to high water/nutrient supply and frequent cutting (Jiang and Huang, 2001a), also dominates on mixed-prairies (Murphy and Grant, 2005;DeKeyser et al, 2010). The rooting depth of Pascopyrum may reach 2 m or deeper into soil profile (Weaver, 1926;Coupland and Johnson, 1965), while for Poa, roots may reach down to 40-45 cm (Gist and Smith, 1948;Peterson et al, 1979;Jiang and Huang, 2001b). These contrasts in rooting depth may depict differences in plants' access to soil moisture (Stewart et al, 2004), as well as in leaf-water relations traits (Krasser and Kalapos, 2000).…”

Mutation in a homolog of yeast Vps53p accounts for the heat and osmotic hypersensitive phenotypes in Arabidopsis hit1-1 mutant

“…Accumulation of solutes to maintain cell turgor has also been associated with heat tolerance in cotton (Ashraf et al 1994). Drought-preconditioned osmotic adjustment can enhance plant heat tolerance as well (Jiang and Huang 2001). Reversely, hightemperature preconditioning can promote osmotic adjustment to increase leaf pressure potential (Morales et al 2003).…”

Comparative Evaluation of Common Savannahgrass on a Range of Soils Subjected to Different Stresses I: Productivity and Quality

“…Contrastingly, CY for all turfgrasses was lowest for D stress, with the effect being particularly pronounced for ZG (Table 4). D stress is known to affect turfgrass physiological and biochemical processes [29], and ZG has been reported to exhibit low D tolerance/resistance [7], which is partially associated with its slow growth rate [30]. Soil compaction has been reported to affect shoot growth [14].…”

“…The ability to recover from drought was related to the extent of drought stress; the longer the drought period, the longer the recovery period. Jiang and Haung [29] stated that, initially, drought reduced the relative water content, but prolonged drought was associated with chlorophyll loss and cell death. ZG retained minimal quality standards under the compactive stresses.…”