Xylem vessel blockages in grape pedicel growing in tropical climate observed by microtomography

In grape berry pedicel, xylem hydraulic conductance can be impaired by blockage deposition in the lumen of xylem elements. However, the varietal difference of the interruptions has not yet been characterized. In this preliminary work, we utilized synchrotron x-ray computed microtomography experiments performed at MOGNO beamline (LNLS – Brazil) to identify possible blockage sites in natural grape pedicel xylem. For this, we imaged dehydrated pedicel’s stem portion from the Niagara Rosada variety in three different phenological stages (Pre-veraison (PreV), veraison (V) and post-veraison (PostV). The reconstructed tridimensional images with a voxel size of 1.16 µm were segmented for the identification of xylem vessel lumens. After analysing one pedicel stem per stage, we identified 658 vessels without occlusion throughout his axial plane and 41 in which we could identify possible interruptions. The percentage of interrupted vessels was higher at PostV (15,58%) when compared to V (4,09%) and PreV (3,14%). At the same time, the vessels’ volume decreased through berry ripening. This may indicate that a higher hydraulic resistance could advance in Niagara Rosada pedicel during development, reducing water flow to the berry. These findings highlight the importance of tools that allow detailed tridimensional histological analysis of intact tissues. Furthermore, we expect to calculate and understand how the water transport throughout the stem pedicel is affected by the growth/ripening changes in blockages, volume vessels and connections between xylem vessels.