Multiple abiotic stress, nitrate availability and the growth of wheat

Y Ge,M.J Hawkesford,C.A Rosolem,S.J Mooney,R.W Ashton,J Evans,W.R Whalley

doi:10.1016/j.still.2019.04.005

Y Ge, M.J Hawkesford + Show 5 more

Open Access

https://doi.org/10.1016/j.still.2019.04.005

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Abstract

In the field, wheat experiences a combination of physical and nutrient stresses. There has been a tendency to study root impedance and water stress in separation and less is known about how they might interact. In this study, we investigated the effect of root impedance on the growth of three wheat varieties (Cadenza, Xi19 and Battalion) at different levels of nitrate availability, from 0–20 mM nitrate, in sand culture. This model system allows soil strength to be increased while maintaining adequate water availability. In a separate pot experiment, we grew the same wheat varieties in a loamy sand where soil was allowed to dry sufficiently to both reduce water potential and increase root impedance. This pot experiment also had a range of nitrate availabilities 0–20 mM nitrate. Once the seedlings were established we limited water supply to apply a matric potential of approximately −200 kPa to the roots. Soil drying increased the penetrometer resistance from approximately 300 kPa to more than 1 MPa. There were differences between the two experimental systems; growth was smaller in the soil-based experiment compared to the sand culture. However, the effects of the experimental treatment, root impedance or water withholding, relative to the control were comparable. Our data confirmed that leaf elongation in Cadenza (carrying the tall Rht allele) was the most sensitive to root impedance. Leaf stunting occurred irrespective of nitrate availability. Leaf elongation in the Xi19 and Battalion (carrying the semi-dwarf Rht allele) was less sensitive to root impedance and drought than Candenza. We suggest that the critical stress in a pot experiment where the soil was allowed to dry to approximately −200 kPa was root impedance and not water availability.

Highlights

While the response of crops to nutrients, in particular nitrogen, has been studied in an agronomic context (e.g. Lawlor et al, 1981), less is known about how nutrient and abiotic stresses interact to determine yield
When soybean was grown for 5 days, Yapa et al (1988) concluded that penetration resistance represents an integration of bulk density and water content, an improved prediction of root penetration into soil cores was possible if the separate components were considered
We have compared the growth of wheat exposed to root impedance either by a confining pressure in a sand culture experiment or by soil drying, at a range of nitrate availabilities

Summary

Introduction

While the response of crops to nutrients, in particular nitrogen, has been studied in an agronomic context (e.g. Lawlor et al, 1981), less is known about how nutrient and abiotic stresses interact to determine yield. Stunting of crop growth in compacted soil by hormonal signalling is likely to contribute to lower yields and this can occur even when nutrient and water supply are adequate (Masle and Passioura, 1987). This is thought to be related to the effects of root impedance. Mechanical impedance can be increased by increasing the confining pressure on a column of sand without any effect on the water or nutrient availability These experiments replicate the effect of root impedance by soil compaction in the

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