Changes In Ploidy Affect Vascular Allometry And Hydraulic Function In Trees

The enucleated vascular elements of the xylem and the phloem offer an excellent system to test the effect of ploidy on plant function because variation in vascular geometry has a direct influence on transport efficiency. However, evaluations of conduit sizes in polyploid plants have remained elusive, most remarkably in woody species. We used a combination of molecular, physiological, and microscopy techniques to model the hydraulic resistance between source and sinks in tetraploid and diploid mango trees. Tetraploids exhibited larger chloroplasts, mesophyll cells, and stomatal guard cells, resulting in higher leaf elastic modulus and lower dehydration rates despite the high water potentials of both ploidies in the field. Both the xylem and the phloem displayed a scaling of conduits with ploidy, revealing attenuated hydraulic resistance in tetraploids. Conspicuous wall hygroscopic moieties in the cells involved in processes of transpiration and transport advocates a role in volumetric adjustments due to turgor change in polyploids, which, together with the enlargement of organelles, cells, and tissues that are critical for water and photoassimilate transport at long distances, imply major physiological novelties of polyploidy.