Spatial dynamics of functional xylem vessels during ‘Palmer’ mango development

Fruit growth depends on the maintenance of vascular transport through xylem vessels, which supply
water and nutrients during development. However, xylem functionality may decline as fruits
develop, affecting their physiology and quality. This study aimed to characterize fruit growth and
quantify spatiotemporal changes in the number of functional xylem vessels during the development
of ‘Palmer’ mangoes, evaluating differences between proximal and distal regions and between
sectors adjacent to the seed and peel. Fruits were sampled weekly from 26 to 96 days after
flowering (DAF), totaling 11 developmental stages and 20 fruit per stage. Fruit mass and the
number of functional xylem vessels were determined in the proximal and distal regions. From 40 to
96 DAF, vessel counts were separated into sectors adjacent to the seed and peel. Mass growth was
fitted using a Gompertz model, whereas vessel counts were analyzed by negative binomial
regression, considering DAF, axial region, radial sector, and their interactions, with standard errors
clustered by fruit. Fruit mass increased from 19.1 ± 6.9 g at 26 DAF to 481.3 ± 92.0 g at 96 DAF,
following a sigmoidal pattern (R² = 0.92). Between 40 and 96 DAF, the number of functional
vessels decreased from 104.45 ± 21.50 to 13.55 ± 7.88 in the proximal region and from 55.45 ±
24.36 to 3.25 ± 4.27 in the distal region, representing reductions of 87.0% and 94.1%, respectively.
Functional xylem loss intensified during fruit growth and was more pronounced in the distal region,
indicating spatial heterogeneity in vascular transport maintenance.