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<Emphasis Type="BoldItalic">Key message</Emphasis> <p><b>Under drought, carbohydrates initially increase in almond tree organs and, ultimately, their root exudates diversify, suggesting shifts in carbon dynamics may impact osmoregulation and exudation under stress.</b></p> Abstract <p>While root exudation allows trees to shape the rhizosphere, mobilize nutrients, and recruit beneficial microbes, it may be costly during abiotic stress like drought and be expected to decrease to conserve carbon (C) for survival. However, the cost of root exudation under typical and stressed conditions remains unknown, especially for tree crops. To determine whether tree crops allocate C to root exudation and if the metabolite profile shifts under drought, we exposed almond saplings to experimental drought, and once stomatal closure was reached, conditions were maintained for 1, 7, or 10 days prior to collecting root exudates for untargeted metabolomics. We also quantified nonstructural carbohydrate (NSC) concentrations in aboveground and belowground organs. Drought plants had higher sugar concentrations in all organs than well-watered controls, suggesting that osmotic adjustment was occurring at the whole-plant level in response to drought. In the roots, total NSC concentrations were higher in the drought plants and declined over time, likely to support respiration and other root-level functions such as root exudation. However, the decrease was small enough that the amount of C allocated to root exudation may have been negligible, and instead root exudates diversified over time. From day 1 to day 10, the number of metabolites that significantly changed between drought and well-watered control plants went from 25 to 332, a nearly 1250% increase. Further, non-metric multidimensional scaling (NMDS) ordination revealed that the metabolite profiles of drought and well-watered plants differed. Overall, our results indicate that diversifying the C compounds exuded into the rhizosphere may be a strategy to maximize the chances of alleviating drought stress, and provides foundational knowledge for future studies to quantify root exudation profiles in other perennial tree crops.</p>

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Nonstructural carbohydrate concentrations and root exudates shift in response to drought in almonds

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月16日

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  • Shreya S. Veeravelli,
  • Anju Manandhar,
  • Bruce R. Cooper,
  • Morgan E. Furze

摘要

Key message

Under drought, carbohydrates initially increase in almond tree organs and, ultimately, their root exudates diversify, suggesting shifts in carbon dynamics may impact osmoregulation and exudation under stress.

Abstract

While root exudation allows trees to shape the rhizosphere, mobilize nutrients, and recruit beneficial microbes, it may be costly during abiotic stress like drought and be expected to decrease to conserve carbon (C) for survival. However, the cost of root exudation under typical and stressed conditions remains unknown, especially for tree crops. To determine whether tree crops allocate C to root exudation and if the metabolite profile shifts under drought, we exposed almond saplings to experimental drought, and once stomatal closure was reached, conditions were maintained for 1, 7, or 10 days prior to collecting root exudates for untargeted metabolomics. We also quantified nonstructural carbohydrate (NSC) concentrations in aboveground and belowground organs. Drought plants had higher sugar concentrations in all organs than well-watered controls, suggesting that osmotic adjustment was occurring at the whole-plant level in response to drought. In the roots, total NSC concentrations were higher in the drought plants and declined over time, likely to support respiration and other root-level functions such as root exudation. However, the decrease was small enough that the amount of C allocated to root exudation may have been negligible, and instead root exudates diversified over time. From day 1 to day 10, the number of metabolites that significantly changed between drought and well-watered control plants went from 25 to 332, a nearly 1250% increase. Further, non-metric multidimensional scaling (NMDS) ordination revealed that the metabolite profiles of drought and well-watered plants differed. Overall, our results indicate that diversifying the C compounds exuded into the rhizosphere may be a strategy to maximize the chances of alleviating drought stress, and provides foundational knowledge for future studies to quantify root exudation profiles in other perennial tree crops.