Root water gates and not changes in root structure provide new insights into plant physiological responses and adaptations to drought, flooding and salinity
The influence of aquaporin (AQP) activity on plant water movement remains unclear, especially in plants subject to unfavorable conditions. We applied a multitiered approach at a range of plant scales to (i) characterize the resistances controlling water transport under drought, flooding and flooding plus salinity conditions; (ii) quantify the respective effects of AQP activity and xylem structure on root (K root ), stem (K stem ) and leaf (K leaf ) conductances, and (iii) evaluate the impact of AQP-regulated transport capacity on gas exchange. We found that drought, flooding and flooding-salinity reduced K root and root AQP activity in Pinus taeda , whereas K root of the flood-tolerant Taxodium distichum did not decline under flooding. The extent of the AQP-control of transport efficiency varied among organs and species, ranging from 35%-55% in K root to 10%-30% in K stem and K leaf . In response to treatments, AQP-mediated inhibition of K root rather than changes in xylem acclimation controlled the fluctuations in K root . The reduction in stomatal conductance and its sensitivity to vapor pressure deficit were direct responses to decreased whole-plant conductance triggered by lower K root and larger resistance belowground. Our results provide new mechanistic and functional insights on plant hydraulics that are essential to quantifying the influences of future stress on ecosystem function.
- Domec, J-C; King, J; Carmichael, M; Overby, AT; Wortemann R, R; Smith, W; Miao, G; Noormets, A; Johnson, D
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