Biology subjects

Marquez, D. A.

Publications and source records attributed to Marquez, D. A..

3 recordsLinked to original sources

bioRxiv2025

Cytosolic water potential as a mechanistic driver of leaf airspace unsaturation and non-stomatal control of transpiration

1Mesophyll cells exhibit a previously underappreciated capacity to regulate water loss via low plasma membrane conductance (Lp), offering a non-stomatal mechanism for transpiration control. However, the structural basis and regulation of Lp remain poorly understood, limiting its integration into predictive models. In this study, we show that Lp responds dynamically to changes in cytosolic water potential ({psi}cy), decreasing as{psi} cy approaches the turgor loss point. This identifies{psi} cy as the primary physiological signal regulating Lp. We introduce a predictive, physiologically grounded model linking Lp to{psi} cy. Our model establishes a mechanistic connection between internal water status, leaf hydraulics, substomatal cavity unsaturation, and gas exchange. This framework opens new avenues for understanding and modelling plant water use under stress.

plant biology↗

bioRxiv2025

Evidence for active regulation of transpiration in non-stomatal plants

O_LIBryophyta (mosses) are a basal group of plants that lack stomata in their haploid form, as well as developed vascular tissue and a hydrophobic cuticle. Consequently, these plants are classified as poikilohydric, meaning poor control over water loss and are often assumed to reach equilibrium with ambient humidity. This classification does not fully align with the diverse strategies observed in mosses. C_LIO_LIWe studied gas exchange in 14 species from Albuquerque and Boston, USA, under controlled dehydration conditions. C_LIO_LIOur results revealed significant variation in transpiration rates, cell wall equilibrium humidity, and desiccation times across species. These differences could not be explained by tissue water storage relative to the transpiring surface area, suggesting that water loss is not entirely passive. Additionally, species with better water control also presented traits of an avoidance strategy, including elastic tissues, high capacitance, and less negative osmotic potential, suggesting an adaptive constraint. C_LIO_LIThese findings point to a basal, non-stomatal mechanism of water loss control through cell membranes and/or cell walls. Potentially, this mechanism is homologous to the non-stomatal control recently identified in angiosperms, which induces unsaturated conditions in the substomatal cavities. Bryophyta presents a valuable non-stomatal model for further investigating this mechanism and its evolutionary significance. C_LI

plant biology↗

bioRxiv2024

Unsaturation and Approximate Isotopic Homogeneity in Leaf Air Spaces

O_LIWe consider two assumptions of leaf isotope gas exchange measurements: that leaf air spaces are saturated with water vapour, and that this vapour is of a homogeneous isotopic composition. In particular, we consider whether these assumptions can concurrently hold and, if not, which assumption is preferable to retain. C_LIO_LIWe present two methods using independent measurements of both leaf surfaces to consider these assumptions. The first method determines the isotopic inhomogeneity between the abaxial and adaxial evaporative sites when saturation is assumed. The second method determines the unsaturation in the abaxial and adaxial substomatal cavities when isotopic homogeneity is assumed. The methods are applied on Gossypium hirsutum (cotton) under benign atmospheric demand conditions (1.0 kPa air saturation deficit). C_LIO_LIWe find evidence that assuming saturation contradicts isotopic homogeneity and vice-versa. We compare each assumption to pre-existing data and find that it is reasonable to assume isotopic homogeneity, but not leaf vapour saturation. Thus, we find that leaves experience unsaturation even under benign atmospheric demand conditions and have a spatial variation in their unsaturation, with lower humidities associated with the surface of least stomatal resistance. C_LIO_LIWe conclude that leaves cannot be considered to be both saturated and of a homogeneous vapour isotopic composition. They are best approximated as isotopically homogeneous. C_LI

plant biology↗