Seed dispersal is critical for plants, but the evolution of mechanisms that actually release seeds from their parents is not well understood. We use the reproductive cones of conifers, specifically the Pinaceae clade, to explore the factors driving the evolution of different release mechanisms in plants.We combine comparative anatomical and phylogenetic analyses to test whether fundamental trade-offs in the mechanical and hydraulic properties of vasculature underlie the evolution of two seed release mechanisms: cone scale flexion and cone scale shedding. We then test whether these mechanisms are linked with differences in seed size, dispersal syndrome and reproductive allocation.Cone scale xylem in flexing species is tough, but poorly conductive. Xylem in shedding species is less extensive, fragile and highly conductive; its thin-walled tracheids allow scales to easily fracture at maturity. Shedding is also consistently associated with large, densely packed seeds.Pinaceae cones exploit a well-known trade-off in xylem mechanical strength vs hydraulic efficiency to generate release mechanisms that allow seeds of various sizes to leave the protecting cone. The linkage among release mechanisms, vascular anatomy and seed traits illustrates how a wide variety of selective pressures may influence the function and physiology of reproductive structures.

The relationships between aerial organ morpho-anatomy of woody polyploid plants with their functional hydraulics under water stress remain largely understudied. We evaluated growth-associated traits, aerial organ xylem anatomy, and physiological parameters of diploid, triploid, and tetraploid genotypes of atemoyas (Annona cherimola x Annona squamosa), which belong to the woody perennial genus Annona (Annonaceae), testing their performance under long-term soil water reduction. The contrasting phenotypes of vigorous triploids and dwarf tetraploids consistently showed stomatal size-density trade-off. The vessel elements in aerial organs were ∼1.5 times wider in polyploids compared with diploids, and triploids displayed the lowest vessel density. Plant hydraulic conductance was higher in well-irrigated diploids while their tolerance to drought was lower. The phenotypic disparity of atemoya polyploids associated with contrasting leaf and stem xylem porosity traits that coordinate to regulate water balances between the trees and the belowground and aboveground environments. Polyploid trees displayed better performance under soil water scarcity, presenting as more sustainable agricultural and forestry genotypes to cope with water stress.

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.