Biology subjects

Farquhar, G. D.

Publications and source records attributed to Farquhar, G. D..

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↗

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↗

bioRxiv2022

A cross-scale analysis to understand and quantify effects of photosynthetic enhancement on crop growth and yield

Photosynthetic manipulation provides new opportunities for enhancing crop yield. However, understanding and quantifying effectively how the seasonal growth and yield dynamics of target crops might be affected over a wide range of environments is limited. Using a state-of-the-art cross-scale model we predicted crop-level impacts of a broad list of promising photosynthesis manipulation strategies for C3 wheat and C4 sorghum. The manipulation targets have varying effects on the enzyme-limited (Ac) and electron transport-limited (Aj) rates of photosynthesis. In the top decile of seasonal outcomes, yield gains with the list of manipulations were predicted to be modest, ranging between 0 and 8%, depending on the crop type and manipulation. To achieve the higher yield gains, large increases in both Ac and Aj are needed. This could likely be achieved by stacking Rubisco function and electron transport chain enhancements or installing a full CO2 concentrating system. However, photosynthetic enhancement influences the timing and severity of water and nitrogen stress on the crop, confounding yield outcomes. Strategies enhancing Ac alone offers more consistent but smaller yield gains across environments, Aj enhancement alone offers higher gains but is undesirable in less favourable environments. Understanding and quantifying complex cross-scale interactions between photosynthesis and crop yield will challenge and stimulate photosynthesis and crop research. Summary StatementLeaf-canopy-crop prediction using a state-of-the-art cross-scale model improves understanding of how photosynthetic manipulation alters wheat and sorghum growth and yield dynamics. This generates novel insights for quantifying impacts of photosynthetic enhancement on crop yield across environments.

plant biology↗