Root system architecture affects water and mineral uptake and is important for plant adaptation to fluctuating nutrient availability. Small signaling peptides and their receptors influence root traits associated with macronutrient uptake. In this study, genome-wide association analyses were performed using 2D images of agar plate-grown Medicago truncatula accessions to understand the impact of GOLVEN10 peptide (GLV10) treatment on three root traits: root tortuosity, lateral root (LR) branch angle, and the gravity setpoint angle (GSA). Upon GLV10 treatment, roots of wild-type M. truncatula Jemalong A17 and R108 accessions showed increased primary root coiling (or tortuosity), increased LR branch angle, and reduced GSA. We identified 88 significant single nucleotide polymorphisms (SNPs) associated with these traits in GLV10-treated plants, distinct from the 163 SNPs in untreated plants. Importantly, the ethylene regulatory pathway was implicated in root tortuosity and LR emergence relative to the primary root. Application of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid reduced root sensitivity to GLV10, while the ethylene signaling mutant sickle was hypersensitive, indicating that GLV10 and ethylene pathways act antagonistically to control root tortuosity. These findings have implications for root gravitropic responses, and the ability of roots to penetrate deeper soil layers for nutrients and water.

This study investigated the effects of drought during reproductive and boll development stages under elevated CO₂ conditions. A pot experiment was conducted in the Soil–Plant–Atmospheric-Research (SPAR) facility using the upland cotton cultivar DP 1646 B2XF grown under control (well-watered; 0.12 m³ H₂O m⁻³ soil) and drought (0.09 m³ H₂O m⁻³ soil) conditions at ambient (425 ppm; aCO₂) and enriched (725 ppm; eCO₂) CO₂ concentrations. Under drought stress, photosynthesis and stomatal conductance decreased by 35% and 63%, respectively, under aCO₂, whereas reductions were less pronounced under eCO₂ (20% and 36%). Under drought and aCO₂, intrinsic and instantaneous water-use efficiency increased by 74% and 45%, respectively, compared to control. Biomass partitioning shifted under drought, with increased allocation to shoots (55%) and roots (9%) and reduced allocation to reproductive organs (36%), compared to control conditions. Flowers produced under drought had 21% fewer ovules under both CO₂ environments, while pollen production remained unaffected. Seed cotton and lint weights were reduced by 19% and 15% under drought, respectively. However, plants grown under eCO₂ attained seed cotton and lint weights that were 20% higher than those grown under aCO₂, under both control and drought conditions. Drought significantly affected fiber quality, increasing micronaire by 26% and reducing fiber length by 4%, regardless of CO₂ level. eCO₂-driven alleviation primarily acts through carbon assimilation and yield compensation, with limited capacity to regulate developmental programming and quality formation.