title: Root xylem plasticity to improve water use and yield in water-stressed soybean.
abstract: We tested the hypothesis that increasing the number of metaxylem vessels would enhance the efficiency of water uptake in soybean (Glycine max) and decrease the yield gap in water-limited environments. A panel of 41 soybean accessions was evaluated in greenhouse, rainout shelter, and rain-fed field environments. The metaxylem number influenced the internal capture of CO2 and improved stomatal conductance, enhancing water uptake/use in soybeans exposed to stress during the reproductive stage. We determined that other root anatomical features, such as cortex cell area and the percentage of stele that comprised cortical cells, also affected seed yield under similar growth parameters. Seed yield was also impacted by pod retention rates under drought stress (24-80 pods/plant). We surmise that effective biomass allocation, that is, the transport of available photosynthates to floral structures at late reproductive growth stages (R6-R7), enables yield protection under drought stress. A mesocosm study of contrasting lines for yield under drought stress and root anatomical features revealed that increases in metaxylem number as an adaptation to drought in the high-yielding lines improved root hydraulic conductivity, which reduced the metabolic cost of exploring water in deeper soil strata and enhanced water transport. This allowed the maintenance of shoot physiological processes under water-limited conditions.
authors.affiliation: University of Missouri, Division of Plant Sciences, Columbia, MO 65211, USA.
authors.forename: Silvas J
authors.initials: SJ
authors.lastname: Prince
authors.affiliation: University of Missouri, Division of Plant Sciences, Columbia, MO 65211, USA.
authors.forename: Mackensie
authors.initials: M
authors.lastname: Murphy
authors.affiliation: University of Missouri, Division of Plant Sciences, Columbia, MO 65211, USA.
authors.forename: Raymond N
authors.initials: RN
authors.lastname: Mutava
authors.affiliation: University of Missouri, Division of Plant Sciences, Columbia, MO 65211, USA.
authors.forename: Lorellin A
authors.initials: LA
authors.lastname: Durnell
authors.affiliation: University of Missouri, Division of Plant Sciences, Columbia, MO 65211, USA.
authors.forename: Babu
authors.initials: B
authors.lastname: Valliyodan
authors.affiliation: University of Missouri, Division of Plant Sciences, Columbia, MO 65211, USA.
authors.forename: J Grover
authors.initials: JG
authors.lastname: Shannon
authors.affiliation: University of Missouri, Division of Plant Sciences, Columbia, MO 65211, USA.
authors.forename: Henry T
authors.initials: HT
authors.lastname: Nguyen
mesh_terms: D018556:Crops, Agricultural / Q000502:physiology*; D003681:Dehydration / Q000503:physiopathology*; D055864:Droughts; D059828:Plant Cells / Q000502:physiology*; D018517:Plant Roots / Q000502:physiology*; D013025:Glycine max / Q000502:physiology; D014867:Water / Q000378:metabolism*; D052584:Xylem / Q000502:physiology*
chemical_list: D014867:Water
keywords: Drought stress; nested association mapping; pod harvest index; pod retention; root anatomy; soybean (Glycine max); yield protection under drought.