Field scale plant water relation of maize (Zea mays) under drought – impact of root hairs and soil texture

Abstract

Background and aims Impact of drought on crop growth depends on soil and root hydraulic properties that determine the access of plant roots to soil water. Root hairs may increase the accessible water pool but their effect depends on soil hydraulic properties and adaptions of root systems to drought. These adaptions are difficult to investigate in pot experiments that focus on juvenile plants. Methods A wild-type and its root hairless mutant maize (Zea mays) were grown in the field in loam and sand substrates during two growing seasons with a large precipitation deficit. A comprehensive dataset of soil and plant properties and monitored variables were collected and interpreted using simulations with a mechanistic root water uptake model. Results Total crop water use was similar in both soils and for both genotypes whereas shoot biomass was larger for the wild type than for the hairless mutant and did not differ between soils. Total final root length was larger in sand than in loam but did not differ between genotypes. Simulations showed that root systems of both genotypes and in both soils extracted all plant available soil water, which was similar for sand and loam, at a potential rate. Leaf water potentials were overestimated by the model, especially for the hairless mutant in sand substrate because the water potential drop in the rhizosphere was not considered. Conclusions A direct effect of root hairs on water uptake was not observed but root hairs might influence leaf water potential dependent growth.

Plant Age and Soil Texture Rather Than the Presence of Root Hairs Cause Differences in Maize Resource Allocation and Root Gene Expression in the Field

“…Alternatively, the root hairs might influence leaf water potential dependent growth. Namely, when cumulative water extraction was normalized to shoot dry weight, Jorda et al (2022) detected higher water use efficiency of WT than rth3 maize [ 41 ]. Lower water use efficiency of rth3 could thus be explained by a more effective regulation of stomata in response to drought [ 50 ], which could also affect respiration rates.…”

“…Within the same field experiment, water transpiration data from Jorda et al (2022) demonstrated that severe water stress occurred just before tassel emergence (BBCH59 stage) [ 41 ]. Water stress is especially detrimental during the reproductive stages when water requirement is the highest [ 74 , 75 , 76 ].…”

“…Following this, we expected pronounced stress-related gene expression in older seedlings. Our second hypothesis stated that there is an increasing effect by substrate during the aging of maize due to nutrient limitation and emerging water stress at the later developmental stages [ 41 ] ( Supplementary Material Figure S1 ). We expected that the substrate effect is characterized by lower leaf nutrient concentrations [ 42 , 43 ] and higher nutrient transporter levels in sand than in loam, as topsoil drying is more detrimental for nutrient availability in sand.…”

Special issue: Rhizosphere spatiotemporal organisation: an integrated approach linking above and belowground

“…Experimental data on the role of soil texture and root hairs for the development of drought stress have been interpreted using modelling approaches at the laboratory scale for the juvenile phase (Köhler et al, 2022) and at field scale during the whole growing period in two consecutive years (Jorda et al, 2022). Jorda et al (2022) show that the root capacity was large enough to absorb all available soil water and that the onset of drought stress was primarily related to shoot size. Neither study could demonstrate a direct influence of roots hairs on soil-plant conductance for the selected maize genotypes, but proved an effect of soil texture on water use.…”

Early root architectural traits and their relationship with yield inIpomoea batatasL

“…Root system architecture is important in natural and managed ecosystems (i.e., forests, pastures, and rangelands), but particularly pertinent to crop production systems, as they are more intensively managed with added inputs (i.e., agrochemicals and irrigation) and improved seed making the latter indispensable for human well-being and progress (Lynch, 2022). Crop growth and yield depend on the ability of the root system to explore, forage, and secure edaphic resources (Qiao et al, 2018; Chen et al, 2022; Jorda et al, 2022). However, root phenotyping research has lagged behind its aboveground counterpart due to the challenging nature of direct selection of root traits under field conditions, which because root systems are underground, requires significant logistical and infrastructure costs, time, and management considerations (Smith and De Smet, 2012; Thomas et al, 2016).…”