Soil Water‐Root Relations in Wheat: Water Extraction Rate of Wheat Roots that Developed under Dry and Moist Conditions¹

Abstract

Prior investigations have reported modifications of various root characters of plants grown under relatively dry soil conditions, but there is a lack of information on the effect of these modifications on the capacity of root systems to extract soil water. This study was therefore conducted to investigate whether the root systems of wheat (Triticum aestivum L.) grown under different soil water conditions differed in their capacity to extract water from the soil. In a greenhouse experiment the water extraction rate per unit root volume was measured for two wheat (Triticum aestivum L.) genotypes grown for 60 days after sowing in pots maintained under three different soil water tension regimes of 0.3 to 0.8, 2.0 to 2.5, and 4.0 to 4.5 bars. The two genotypes under study were one gene dwarf Sonalika RR‐21 and three gene dwarf UP 301. The soil used was silty clay loam of the Mollisol order. Beginning on the 60th day after sowing the transpirational losses under different soil water tension regimes were measured for a period of 12 days by covering the pots with polyethylene sheet and weighing them intermittently. At the end of this 12‐day period volume, length, and dry weight of the roots were measured. The water extraction rate per unit root volume was calculated assuming that the transpirational loss was the amount of water extracted by the roots in a linear proportion to the root volume. The water extraction rate per unit root volume increased significantly with increasing soil water tension regimes. It varied from 7.91 cm3 H2O cm−3 root day−1 for UP 301 under the wettest regime of 0.3 to 0.8 bar to 9.11 cm3 H2O cm−3 root day−1 for Sonalika RR‐21 under the driest regime of 4.0 to 4.5 bar tensions. These findings suggest that root systems that developed under relatively dry soil conditions were capable of extracting greater amount of soil water on a unit root volume basis than those developed under moist conditions.

MORPHOLOGICAL AND ANATOMICAL EFFECTS OF SEVERE DROUGHT ON THE ROOTS OF LOLIUM PERENNE L.

“…Other reports of increased lateral root proliferation (e.g. Sharma & Ghildyal, 1977;Osonubi & Davies, 1978;Huck et al, 1983) in response to drought have commonly used considerably higher soil water potentials than those used in the present study. This information therefore appears to be the first to suggest that roots may respond to a severe drought by producing new lateral roots at SMPs as low as -6 to -8 MPa.…”

Root system plasticity to drought influences grain yield in bread wheat

“…Furthermore, a vigorous shallow root system is required for absorption of nutrients that are mostly concentrated in the upper layers of soil (Manske and Vlek 2002). Increases in root system traits in response to drought stress were first reported in plants by Muller-Thurgau (1875); and subsequently there were specific reports for maize (Zea mays L.) (Sharp and Davies 1979), wheat (Sharma and Ghildyal 1977), and soybean (Glycine max L.) (Huck et al 1983).…”

Root growth and soil-water extraction by winter and spring wheat

“…Schurmann (1959) and Proffitt et al (1985) reported that when water supply in the upper soil profile was plentiful, rooting depth remained shallow. Sharma and Ghildyal (1977) observed that drier soil conditions promoted root elongation and increased the degree of branching, allowing the crop to exploit soil water more completely. However, Barraclough et al (1989) reported that wheat crops do not necessarily exhaust all available soil water before commencing uptake from the next deeper layer.…”