Above and belowground traits impacting transpiration decline during soil drying in 48 maize (Zea mays) genotypes

Abstract

Background and Aim Stomatal regulation allows plants to promptly respond to water stress. However, our understanding of the impact of above and belowground hydraulic traits on stomatal regulation remains incomplete. The objective of this study was to investigate how key plant hydraulic traits impact transpiration of maize during soil drying. We hypothesize that stomatal response to soil drying is related to a loss in soil hydraulic conductivity at the root-soil interface, which in turn depends on plant hydraulic traits. Methods We investigate the response of 48 contrasting maize (Zea mays L.) genotypes to soil drying, utilizing a novel phenotyping facility. In this context, we measure the relationship between leaf water potential, soil water potential, soil water content and transpiration, as well as root, rhizosphere and aboveground plant traits. Key Results Genotypes differed in their responsiveness to soil drying. The critical soil water potential at which plants started decreasing transpiration was related to a combination of above- and belowground traits: genotypes with a higher maximum transpiration and plant hydraulic conductance as well as a smaller root and rhizosphere system closed stomata at less negative soil water potentials. Conclusions Our results demonstrate the importance of belowground hydraulics for stomatal regulation and hence drought responsiveness during soil drying. Furthermore, this finding supports the hypothesis that stomata start to close when soil hydraulic conductivity drops at the root-soil interface.

Transpiration response to soil drying versus increasing vapor pressure deficit in crops: physical and physiological mechanisms and key plant traits

“…5A ). This was also shown by Cai et al (2022a) for several plant species (namely: wheat, barley, maize, and tomato) and Koehler et al (2023) for maize ( Fig. 5B ).…”

“…Note that in Fig. 5B , Koehler et al (2023) included the maximum transpiration (as a measure of plant water demand) divided by root surface area (as a measure of plant water supply), besides the plant hydraulic conductance, as a factor determining the onset of soil hydraulic limitations. The reasoning behind the counterintuitive relation between plant hydraulic conductance and ψ soil is explained in the following.…”

Rhizosheath drought responsiveness is variety‐specific and a key component of belowground plant adaptation

“…The experiment was terminated at 64 DAS, when all plants under drought were stressed enough to reduce transpiration rates by at least 50% (NTR ≤ 0.5, Koehler et al ., 2023). The final water contents in well‐watered and drought‐stressed mesocosms at sampling were 22.7 ± 3.5 vol‐% and 9.9 ± 1.5 vol‐%, corresponding to pF values of 1.9 and pF 4.2.…”

“…Before the dry down, the soil surface was covered with plastic beads (PP copolymer) to reduce soil evaporation. The drying process was monitored gravimetrically by weighing the pots daily to calculate the normalized transpiration ratio (NTR) from the weight differences between consecutive days (for details, see Koehler et al, 2023). 13.9 N (mgN g À1 soil)…”

Enhancing maize resilience to drought stress: the synergistic impact of deashed biochar and carboxymethyl cellulose amendment

“…Drought poses a significant threat to maize production, affecting yield and quality [ 1 – 3 ]. Maize is highly vulnerable to water stress during crucial growth stages, leading to stunted growth and reduced yields [ 4 , 5 ]. This emphasizes the need for adaptive measures, such as water-efficient farming practices, to safeguard global food security [ 6 ].…”