Dissecting and modelling the comparative adaptation to water limitation of sorghum and maize: role of transpiration efficiency, transpiration rate and height

E J Van Oosterom,G B Mclean,M R D L Kulathunga,G L Hammer,C Messina,C Barrasso,K S Deifel,A Wu

doi:10.1093/insilicoplants/diaa012

Abstract

Abstract Maize is considered less drought-tolerant than sorghum, but sorghum is commonly grown as a short triple dwarf (3dwarf) type, so difference in plant height confounds the species comparison. The objectives of this study were to experimentally determine effects of species and plant height differences on transpiration efficiency (TE) and transpiration rate per unit green leaf area (TGLA) and use findings to explain input parameters in a simulation study on the comparative adaptation of 3dwarf sorghum and maize in environments with contrasting water availability. Maize, tall double dwarf (2dwarf) and short 3dwarf sorghum genotypes were grown in two lysimeter experiments in 2011 in SE Queensland, Australia. Each plant was harvested after anthesis and total transpiration, shoot and root dry mass were measured to estimate TE. Daily TGLA was used to compare transpiration rates. Species and height had limited effect on TE, but significantly affected TGLA. This was associated with differences in biomass allocation. The similar TE but higher TGLA in maize compared with 3dwarf sorghum meant it potentially produces more biomass, consistent with published differences in biomass accumulation and radiation use efficiency (RUE). The simulation study, which used similar TE for maize and 3dwarf sorghum, but captured differences in TGLA through differences in RUE, predicted crossover interactions for grain yield between species and total water use. The greater TGLA of maize decreased grain yield in water-limited environments, but increased yields in well-watered situations. Results highlight that similarity in TE and differences in TGLA can influence comparative adaptation to water limitation.

Highlights

Maize and sorghum are major summer crops in rainfed farming systems around the world
Results highlight that similarity in transpiration efficiency (TE) and differences in transpiration rate per unit green leaf area (TGLA) can influence comparative adaptation to water limitation
0.01 ns these dates, TGLA of 2dwarf sorghum increased to the level of the maize, as the slope of the relationship did not differ significantly from unity (0.99 ± 0.044, Fig. 1B), but it was significantly greater than 3dwarf sorghum, as the slope of the relationship (Fig. 1C) was significantly greater than unity (1.34 ± 0.041)

Summary

Introduction

Maize and sorghum are major summer crops in rainfed farming systems around the world. The enhanced tolerance of sorghum to water limitation compared to maize has been associated with a shorter crop cycle and lower crop growth rate, both of which impact on the total amount of water transpired. This is important, as grain yield under end-of-season drought stress is closely related to the amount of water available for transpiration to sustain growth during grain filling (Turner 2004; Hammer 2006; Borrell et al 2014). Greater transpiration rates associated with greater biomass growth can hasten the onset of water limitation in maize crops

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Methods

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Conclusion