Temporal and spatial patterns of soil water extraction and drought resistance among genotypes of a perennial C4 grass

Abstract

The objective of this study was to investigate patterns of soil water extraction and drought resistance among genotypes of bermudagrass (Cynodon spp.) a perennial C 4 grass. Four wild Australian ecotypes (1-1, 25a1, 40-1, and 81-1) and four cultivars (CT2, Grand Prix, Legend, and Wintergreen) were examined in field experiments with rainfall excluded to monitor soil water extraction at 30-190 cm depths. In the study we defined drought resistance as the ability to maintain green canopy cover under drought. The most drought resistant genotypes (40-1 and 25a1) maintained more green cover (55-85% vs 5-10%) during water deficit and extracted more soil water (120-160 mm vs 77-107 mm) than drought sensitive genotypes, especially at depths from 50 to 110 cm, though all genotypes extracted water to 190 cm. The maintenance of green cover and higher soil water extraction were associated with higher stomatal conductance, photosynthetic rate and relative water content. For all genotypes, the pattern of water use as a percentage of total water use was similar across depth and time We propose the observed genetic variation was related to different root characteristics (root length density, hydraulic conductivity, root activity) although shoot sensitivity to drying soil cannot be ruled out.

Drought responses of above‐ground and below‐ground characteristics in warm‐season turfgrass

“…Surface soil drying is very common during progressive drought and can have a profound impact on root growth, viability and functionality in turfgrass (Huang, 1999). In another study involving bermudagrass, Zhou, Lambrides, Roche, Duff, and Fukai (2013) reported that drought resistant genotypes extracted more soil water than drought sensitive ones, especially at depths from 50-110 cm, resulting in lower canopy temperature, higher photosynthetic rates and relative water contents in leaves. Fuentealba et al (2015) also reported more uniform root distribution throughout the soil profile in common bermudagrass.…”

Physiological Responses to Soil Drying by Warm‐Season Turfgrass Species

“…A relatively comprehensive study in Australia involving 18 bermudagrass genotypes reported that drought‐resistant genotypes extracted more soil water than drought‐sensitive ones, especially at depths from 50 to 110 cm with lower canopy temperature, higher photosynthetic rate, and relative water content in the leaf. Although root characteristics played a large role in the drought responses of turfgrass, shoot sensitivity to drying soil cannot be ruled out (Zhou et al, 2013, 2014).…”

Associations between drought resistance, regrowth and quality in a perennial C4 grass

“…Consequently, for the first time we show that for turfgrasses there is no adverse effect of selecting for drought resistance in terms of production attributes and quality. In the turfgrass industry, faster regrowth rate after sod removal and a longer period of green cover after drought commences are the criteria for high productivity potential and superior drought resistance, respectively Richardson et al, 2008;Zhou et al, 2013a;Zhou et al, 2013b;Emmons 2008). The positive association between these two criteria lead us to conclude that the mechanisms of plant response are most likely related.…”

“…The pleiotropic effects of selection for drought resistance are not well understood in perennial C 4 grasses. For turfgrasses, the ability to maintain green cover for longer periods under water deficit is an important criterion of drought resistance Richardson et al, 2008;Zhou et al, 2013a;Zhou et al, 2013b). In terms of production, sod strength and rapid regrowth in non-stress conditions after harvest are important criteria (Emmons 2008).…”

“…As turfgrasses, commercial bermudagrasses have been widely used in sports fields, gardens and roadsides, in North America, Europe, Asia, South America, Africa and Australia. We have recently collected over 1000 bermudagrass ecotypes from a wide range of Australian climatic zones and screened 436 of these for drought resistance in the field (Kearns et al, 2009;Zhou et al, 2012;Zhou et al, 2013a;Zhou et al, 2013b). Subsequently, 12 genotypes contrasting for drought resistance were used to study mechanisms of resistance including water extraction patterns by investigating above and below ground traits (Zhou et al, 2014).…”