Petal number is highly canalised in the four-petalled flowers of Arabidopsis. This trait is decanalised in the closely related species Cardamine hirsuta, such that petal number varies from zero to four between individual flowers and in response to natural genetic and environmental variation. Loss of robustness was traced to divergence of the MADS-box transcription factor APETALA1 in C. hirsuta, resulting in loss of epistasis over alleles that cause petal number to vary. How petal formation is patterned in these decanalised flowers is an open question. Here we use genetics and quantitative imaging to investigate how a key patterning module, comprising CUP-SHAPED COTYLEDON1,2 (CUC) transcription factors and auxin, regulates petal formation in C. hirsuta. We show that auxin activity maxima are positioned in inter-sepal boundaries, rather than on the floral meristem, rendering petal initiation sensitive to the space available between sepals, such that growth variation influences petal number variation.

Fruit growth is driven by the interaction of environmental cues and phytohormonal signals. Biophysical models have captured the general trend of fruit growth but often overlook the regulatory role of phytohormones. This study integrates a biophysical framework with the quantitative response of endogenous abscisic acid (ABA) in fruit. ABA dynamics are incorporated as a ripening signal, influencing sugar uptake, respiration, hydraulic conductance and transpiration processes. The model has been primarily tested on blueberries, a fruit with well-characterised ABA responses. Simulations show predictive accuracy and explanatory capability for fruit mass under variable climatic conditions. Notably, the model effectively simulates the impacts of environmental stresses such as heat, cold and drought, capturing the resulting physiological delays in fruit growth. Our research underscores the potential of integrating phytohormonal responses into biophysical models, providing key insights into fruit growth dynamics and practical guidance for optimising crop management under increasing climate uncertainties.

The micronutrient chloride (Cl―) plays key roles in plant physiology, from photosystem II and vacuolar ATPase activity to osmoregulation, turgor maintenance and drought resilience, while also posing toxicity risks at high concentrations. This review examines Cl― uptake, transport and homeostasis, focussing on adaptations balancing its dual roles as a nutrient and toxicant. Key transporters, including NPF, SLAH, ALMT, CLC and CCC families, mediate Cl― fluxes to maintain ionic balance and prevent toxicity. Plants employ strategies such as selective uptake and vacuolar compartmentalization to cope with high salinity. Cl― also influences nitrogen-use efficiency and plant productivity. Advances in transporter biology reveal the role of Cl― in water-use efficiency, drought resilience and stress adaptation.

As the catalytic centre of the oxygen-evolving complex in photosystem II and a co-factor of glycosyltransferases and many other proteins, manganese (Mn) is essential for plants and a limiting factor for crop production. However, an excessive Mn availability is toxic to plants. Therefore, mechanisms need to be in place to maintain Mn homeostasis under fluctuating Mn availability. This review summarises our current understanding of the mechanisms that move Mn from the soil to its cellular targets and maintain Mn homeostasis. We zoom in from the whole-plant perspective to the intracellular allocation of the metal by transport proteins of different families acting in concert. In particular, organellar Mn supply by members of the recently identified bivalent cation transporter family and the post-translational regulation of Mn transporters by calcium-regulated phosphorylation have been a focus of current research. Finally, the emergent diversity of Mn handling beyond the Arabidopsis model will be addressed.

Hydrogen, a deceptively simple element, plays crucial roles in regulating life on Earth. The concentration of hydrogen ions (H+) determines the pH of biological systems and dictates virtually all biochemical processes. The pH modulates the structure, physicochemical properties and function of most macromolecules. The plant cell surface is characterized by tremendous variations in apoplastic pH, serving as informative signals shaping plant development and its interaction with the environment. Here, we discuss the principles underlying cell surface H+ homeostasis, the molecular tipping points that regulate fast, controlled and informative changes in apoplastic pH, as well as open questions regarding the regulation of plasma membrane H+-ATPases.

Plants develop characteristic shoot architectures by extending branches at specific angles. Primary shoots bend in response to gravity and then adjust the orientation through an organ-straightening process to achieve a mechanically favorable shape. However, how plants integrate branch structure with the shoot architecture remains uncertain. Here, we examined the lateral branch morphology of Arabidopsis thaliana mutants for myosin XI motor proteins through a combination of three-dimensional reconstruction and temporal imaging. The wild type and myosin xif mutant formed S-shaped branches and gradually adjusted the branch angle upwards. The myosin xik mutant exhibited straighter and drooping branches and maintained branch angles. The myosin xif xik double mutant formed branches with irregular directional changes with fluctuating angles. These results suggest that MYOSIN XIk and XIf are required for the establishment of branch morphology through upward bending, stabilizing growth direction, and maintaining curvature.

Iron (Fe) is an essential element in plants, involved in numerous metabolic processes including photosynthesis. Its cellular concentration must be regulated accurately to avoid toxicity while meeting metabolic demands. This review explores the distribution, dynamics, and regulation of Fe pools in plant cells, focusing on recent advances in imaging and quantification techniques. We discuss the major Fe compartments—chloroplasts, vacuoles, apoplasts—and their interaction to maintain Fe homeostasis, as well as novel methodologies like single-cell ICP-MS that have transformed our understanding of Fe localization. By summarizing the current knowledge on intracellular Fe dynamics and the complex interplay between different Fe pools, we provide insights into the mechanisms that underpin Fe regulation in plants, which is crucial for future breeding programs aimed at improving plant resilience and nutritional quality.

Potassium is an essential macronutrient required for plant growth and development. Over the recent decade, an important signalling role of K+ has emerged. Here, we discuss some aspects of such signalling at the various levels of plant functional organisation. The topic covered include: (1) mechanisms of long-distant K+ transport in the xylem and phloem and the molecular identity and regulation of K+ loading and unloading into plant vasculature; (2) essentiality and physiological roles of K+ cycling between shoots and roots; (3) plant sensing and signalling of low K+; (4) maintenance of K+ homeostasis at the cellular level; (5) stress-induced modulation of cytosolic K+ as a signal in plant adaptive responses to hostile environment; (6) stress-specific K+ “signatures” and mechanisms of their decoding by regulation of purine metabolism and H+-ATPase activity; (7) cytosolic K+ loss as a metabolic switch and a regulator of autophagy; and (8) vacuolar K+ transport and sensing.

Eucalyptus cladocalyx, known for its drought tolerance, has complex wood anatomy influenced by environmental conditions. This study investigated the xylem response of E. cladocalyx seedlings to cyclic drought stress compared to continuous irrigation. Seedlings were subjected to alternating drought and watering cycles, and their growth, xylem traits and cambial activity were monitored. Continuously irrigated seedlings exhibited greater height and stem diameter growth than periodically irrigated ones. Xylem response between the periodic and continuous irrigations showed no significant differences. Vessel and fibre features showed significant temporal variation, with substantial interaction between treatment and time for vessel area, fibre area and fibre thickness and not for vessel frequency. The cambium remained active under drought conditions, indicating resilience. Overall, anatomical properties varied complexly and inconsistently across drought cycles, likely due to differences in drought intensity, strategies and genetic factors.

Maple sugaring is a rapidly growing industry in North America. Maples are tapped annually, thus undergoing repeated wounding and resource reduction for sap water collection. We aim to understand the effects of tapping and sap exudation on annual radial wood growth and xylem traits in sugar maple (Acer saccharum Marsh.), utilizing eight mature trees monitored during 2018-2021 in Simoncouche, Canada. Compared to the first year of tapping, trees exhibited a 49.7% drop in tree-ring width. Vessel density, potential hydraulic conductivity and hydraulic vessel diameter decreased, but not lumen area. We showed evidence of a trade-off among sap extraction, resource depletion and reduced tree growth. The repeated reduction of resources through tapping can have a detrimental effect on tree growth, even if the effect on the hydraulic function remains marginal. These insights underscore the need for sustainable tapping practices that consider the long-term health and productivity of sugar maple trees.

The micronutrient zinc (Zn) is often poorly available but toxic when present in excess, so a tightly controlled Zn homoeostasis network operates in all organisms. This review summarizes our present understanding of plant Zn homoeostasis. In Arabidopsis, about 1,900 Zn-binding metalloproteins require Zn as a cofactor. Abundant Zn metalloproteins reside in plastids, mitochondria and peroxisomes, emphasizing the need to address how Zn reaches these proteins. Apo–Zn metalloproteins do not acquire Zn2+ from a cytosolic pool of free cations, but instead through associative ligand exchange from Zn-buffering molecules. The importance of cytosolic thiols in Zn buffering suggests that, besides elevated Zn influx, a more oxidized redox state is also predicted to cause elevated labile-bound Zn levels, consistent with the suppression of a Zn deficiency marker under oxidative stress. Therefore, we consider a broadened physiological scope in plants for a possible signalling role of Zn2+, experimentally supported only in animals to date.

The preference towards colourful patterns generates many aesthetic biases, including in Biology research, leading to taxonomic preferences and understudied groups, including many plant taxa. After reviewing the importance of aesthetics in Turing colour pattern studies and the relative nature of the sense of beauty in Biology, I present a method called SE (せ) that strongly reduces taxonomic preferences in colour pattern formation studies, together with allowing the exploration of colour patterns biodiversity and facilitating the discovery of new morphogenesis processes.

How robust three-dimension (3D) organ shape emerges during morphogenesis is a fundamental question in biology. Addressing this question requires a comprehensive quantification of organ geometry in 3D. To tackle these issues, we considered the sepal of Arabidopsis as a model. Using a unique pipeline allowing to recover 3D sepal morphology, we analysed fifteen mutants affected in different pathways. The results of a Principal Component Analysis reveal sepal curvature as an important parameter accounting for variations in sepal morphology within genotypes. Unexpectedly, despite genetic homogeneity of the wild-type plants and reproducible culture conditions, we found a significant level of variability in sepal morphology. Our data also show that sepal shape from wild-type plants is more robust (less variable) than sepal size, hinting to a possible selective pressure on shape parameters.

Homeostats are important to control homeostatic conditions. Here, we have analyzed the theoretical basis of their dynamic properties by bringing the K homeostat out of steady state (i) by an electrical stimulus, (ii) by an external imbalance in the K+ or H+ gradient or (iii) by a readjustment of transporter activities. The reactions to such changes can be divided into (i) a short-term response (tens of milliseconds), where the membrane voltage changed along with the concentrations of ions that are not very abundant in the cytosol (H+ and Ca2+), and (ii) a long-term response (minutes and longer) caused by the slow changes in K+ concentrations. The mechanistic insights into its dynamics are not limited to the K homeostat but can be generalized, providing a new perspective on electrical, chemical, hydraulic, pH and Ca2+ signaling in plants. The results presented here also provide a theoretical background for optogenetic experiments in plants.

Plant synthetic biology is a rapidly advancing multidisciplinary research area that applies engineering principles to design, construct, and implement new plant capabilities at the molecular, cellular, and whole organism scales. Synthetic gene circuits are important tools for enabling increased customizability in the control of gene expression in plants, with widespread applications spanning new approaches for basic biology to introduction of new traits for advancing agriculture. In this review, we first aimed to provide a comprehensive understanding of synthetic circuits. Next, we discuss recent progress in the construction of advanced synthetic gene circuits in plants for programmable control of gene expression. Finally, we discuss the current challenges associated with developing and applying effective circuits while also highlighting future prospects and research directions, including quantitative measurement, high-throughput testing, and circuit modelling.

Calcium ions (Ca2+) play pivotal roles in a host of cellular signalling processes. The requirement to maintain resting cytosolic Ca2+ levels in the 100–200 nM range provides a baseline for dynamic excursions from resting levels that determine the nature of many physiological responses to external stimuli and developmental processes. This review provides an overview of the key components of the Ca2+ homeostatic machinery, including known channel-mediated Ca2+ entry pathways along with transporters that act to shape the cytosolic Ca2+ signature. The relative roles of the vacuole and endoplasmic reticulum as sources or sinks for cytosolic Ca2+ are considered, highlighting significant gaps in our understanding. The components contributing to mitochondrial, chloroplast and nuclear Ca2+ homeostasis and organellar Ca2+ signals are also considered. Taken together, a complex picture of the cellular Ca2+ homeostatic machinery emerges with some clear differences from mechanisms operating in many animal cells.

In the current polycrisis era, plant science, particularly when applied to agronomy, becomes instrumental: because our main substantial and renewable resource is plant biomass, many future solutions will depend on our ability to grow and transform plant material in a sustainable way. This also questions the way we conduct plant research and thus quantitative plant biology. In response to the increasing polarization between science and society, participatory plant research offers a pertinent framework. Far from moving away from quantitative approaches, participatory plant research builds on complexity associated with biology and situated knowledge. When researchers and citizens work together on societal issues, such friction becomes more fertile, quantitative questions become more complex, societal issues are addressed at their roots and outcomes often exceed that of top-down strategies. This article serves as an introduction to this ongoing bifurcation in plant science, using plant breeding as a key example.

Phosphorus (P) is a non-renewable resource that limits plant productivity due to its low bioavailability in the soil. Large amounts of P fertilizer are required to sustain high yields, which is both inefficient and hazardous to the environment. Plants have evolved various adaptive responses to cope with low external P availability, including mobilizing cellular P through phosphate (Pi) transporters and recycling Pi from P-containing biomolecules to maintain cellular P homeostasis. This mini-review summarizes the current research on intracellular P recycling and mobilization in response to P availability. We introduce the roles of Pi transporters and the P metabolic enzymes and expand on their gene regulation and mechanisms. The relevance of these processes in the search for targets to improve phosphorus use efficiency and some of the current challenges and gaps in our understanding of P starvation responses are discussed.

The development of the water transporting xylem tissue in plants involves an intricate interplay of Rho-of-Plants (ROP) proteins and cortical microtubules to generate highly functional secondary cell wall patterns, such as the ringed or spiral patterns in early-developing protoxylem. We study the requirements of protoxylem microtubule band formation with simulations in CorticalSim, extended to include finite microtubule persistence length and a novel algorithm for microtubule-based nucleation. We find that microtubule flexibility facilitates pattern formation for all realistic degrees of mismatch between array and pattern orientation. At the same time, flexibility leads to more density loss, both from collisions and the microtubule-hostile gap regions, making it harder to maintain microtubule bands. Microtubule-dependent nucleation helps to counteract this effect by gradually shifting nucleation from the gap regions to the bands as microtubules disappear from the gaps. Our results reveal mechanisms that can result in robust protoxylem band formation.

In ‘The chemical basis of morphogenesis’ (1952), Alan Turing introduced an idea that revolutionised our thinking about pattern formation. He proposed that diffusion could lead to the spontaneous formation of regular patterns. Here, we discuss the impact of Turing’s idea on plant science using three well-established examples at different scales: ROP patterning inside single cells, epidermal patterning across several cells and whole vegetation patterns. Also at intermediate levels, e.g., organ spacing, plants look surprisingly regular. But not all regular patterns are Turing patterns, careful observation and prediction of the patterning process—not just the final pattern—is critical to distinguish between mechanisms.