Hydraulic tradeoffs underlie enhanced performance of polyploid trees under soil water scarcity

Abstract

Polyploid trees are excellent candidates to reduce crop water footprint and mitigate the increasingly reduced availability of freshwater for irrigation in many regions of the world due to climate change. Yet, the relationships between aerial organ morpho-anatomy of woody polyploids with their functional hydraulics under water stress remain understudied. We evaluated growth-associated traits, aerial organ xylem anatomy, and physiological parameters of diploid, triploid, and tetraploid genotypes of the woody perennial genus Annona (Annonaceae), testing their performance under long-term soil water reduction. Polyploids displayed contrasting phenotypes, vigorous triploids and dwarf tetraploids, but consistently showed stomatal size-density trade-off. The vessel elements in aerial organs were ~1.5 times wider in polyploids compared with diploids, but triploids displayed the lowest vessel density. Sap flow velocity, measured in vivo through a novel method, was 10-fold faster in flower carpels than in second leaf vein orders. Triploid leaves displayed the slowest velocity in the leaves but the fastest in the carpels. Plant hydraulic conductance was higher in well-irrigated diploids at the cost of consuming more belowground water, but diploids showed less tolerance than polyploids to soil water deficit. The phenotypic disparity of atemoya polyploids associates with contrasting leaf and stem xylem porosity traits that coordinate to regulate water balances between the trees and the belowground and aboveground environment. Polyploid trees displayed a better performance under soil water scarcity, opening the possibility for deeper research on the factors underlying this behaviour and use them for a more sustainable agricultural and forestry production.