Biology subjects

Hormaza, J. I.

Publications and source records attributed to Hormaza, J. I..

5 recordsLinked to original sources

bioRxiv2026

Continuous monitoring of deficit irrigation in avocado across two contrasting rainfall years using sensor networks, telemetry, and machine learning

Water scarcity and increasingly irregular rainfall threaten avocado production in Mediterranean regions, yet the long term physiological responses of mature trees to sustained deficit irrigation remain poorly understood. We conducted a two-year field study integrating continuous monitoring of the soil plant atmosphere continuum, drone-based multispectral imaging, canopy structural analysis, and fruit phenotyping in a mature avocado orchard subjected to three irrigation regimes. The two study years differed markedly in rainfall, providing a unique opportunity to evaluate how environmental conditions modulate tree responses to water limitation. Trees under severe deficit irrigation showed depletion of water in deeper soil layers and a flattened physiological profile, with near-zero diel variation in leaf thickness and trunk water potential, indicating minimal transpiration and decoupling of tree water status from environmental demand. Drone telemetry via NDVI detected stress during fruit growth and maturation, but not during flowering or the new summer leaf flush, revealing greater drought sensitivity at later maturation stages. Although canopy area did not differ among irrigation treatments, canopy surface roughness increased significantly under deficit irrigation, thereby identifying a novel structural indicator of drought stress. Despite large physiological differences among treatments, fruit number remained stable, while fruit weight decreased significantly under severe deficit irrigation, particularly in the wetter year, suggesting that annual rainfall modulates the trade-off between fruit retention and fruit growth. This study provides the first continuous, multi-scale characterization of avocado performance under sustained deficit irrigation in Mediterranean conditions. By integrating plant-based sensors, remote sensing, and artificial intelligence, we reveal previously undescribed stress dynamics and identify new indicators for precision irrigation management in fruit crops.

plant biology↗

bioRxiv2025

Apomixis frequency in polyploid wild populations of Psidium cattleyanum f. lucidum (Myrteae, Myrtaceae)

Background and AimsApomictic reproduction and polyploidy are closely related in plants, and their causes and consequences have given rise to numerous hypotheses that continue to evolve as more representative taxa are studied. Psidium cattleyanum is a valuable model for investigating this relationship, as it is a polyploid species with multiple ploidy levels and exhibits pseudogamous gametophytic apomixis. In addition, it is a fruit tree of commercial, agricultural, and medicinal interest in its native range, but it is also an aggressive invasive species in regions where it has been introduced. In this study, we aim to determine the predominant reproductive mode in natural populations of the polyploid Psidium cattleyanum f. lucidum and to investigate whether this mode is associated with specific ploidy levels. Furthermore, we investigate whether these reproductive traits are linked to patterns of genetic diversity and population genetic structure. MethodsWe assessed the reproductive mode in wild populations representing the four ploidy levels (2C = 5x, 6x, 7x, 8x) present in Uruguay. Reproductive pathways were inferred by combining flow cytometric seed screen (FCSS) analysis with microsatellite (SSR) genotyping of progeny arrays. Population-level differences were evaluated across both data sets. Key ResultsPseudogamous apomixis is the predominant reproductive mode in Uruguayan P. cattleyanum f. lucidum populations. The proportions of apomictic versus sexual reproduction, and the types of progenies produced, differed significantly among populations and ploidy levels. Genotyping revealed predominantly clonal progeny, yet with high genetic variability, and populations exhibit strong genetic structure. The ploidy level of the gametes and their combinations were characteristic of each population, leading to different reproductive strategies. ConclusionsFacultative pseudogamous apomixis is the primary reproductive mode in natural populations of Psidium cattleyanum f. lucidum. Ploidy level influences reproductive strategy, as reflected in the apomixis/sexuality ratios and the type of progeny produced. Population genetic structure is shaped by the reproductive strategy adopted by each population.

plant biology↗

bioRxiv2022

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

O_LIPolyploid 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. C_LIO_LIWe 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. C_LIO_LIPolyploids 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. C_LIO_LIThe 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. C_LI

plant biology↗

bioRxiv2021

Changes In Ploidy Affect Vascular Allometry And Hydraulic Function In Trees

O_LIThe 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. C_LIO_LIWe used a combination of molecular, physiological, and microscopy techniques to model the hydraulic resistance between source and sinks in tetraploid and diploid mango trees. C_LIO_LITetraploids 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. C_LIO_LIConspicuous 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 photo assimilate transport at long distances, imply major physiological novelties of polyploidy. C_LI

plant biology↗

bioRxiv2021

Conductivity of the phloem in Mangifera indica L.

Mangifera indica is the fifth most consumed fruit worldwide, and the most important in tropical regions, but its anatomy is quite unexplored. Previous studies examined the effect of chemicals on the xylem structure in the stems of mango, but the anatomy of the phloem has remained elusive, leaving the long distance transport of photo assimilates understudied. In this work, we used a combination of fluorescence and electron microscopy to evaluate in detail the structure of the sieve tube elements composing the phloem tissue in the tapering branches of mango trees. We then used this information to better understand the hydraulic conductivity of the sieve tubes following current models of fluid transport in trees. Our results revealed that the anatomy of the phloem in the stems changes from current year branches, where it was protected by pericyclic fibers, to older ones, where the lack of fibers was concomitant with laticiferous canals embedded in the phloem tissue. Callose was present in the sieve plates, but also in the walls of the phloem conduits, making them discernible from other phloem cells in fresh sections. A scaling geometry of the sieve tube elements, including the number of sieve areas and the pore size across tapering branches resulted in an exponential conductivity from current year branches to the base of the tree. Our measurements of the phloem in mango fit with measurements of the phloem architecture in the stems of forest woody species, and imply that, despite agronomic pruning practices, the sieve conduits of the phloem scale with the tapering branches. As a result, the pipe model theory applied to the continuous tubing system of the phloem appears as a good approach to understand the "long distance" hydraulic transport of photoassimilates in fruit trees.

plant biology↗