William W. Adams

Interfacing bioelectronic devices with plants can enable nature-based sensing networks by transducing electrical signals from living plants into real-time environmental data. A key challenge in developing such platforms is to create stable, biocompatible electrodes that provide sufficient adhesion to plant tissue with minimal impedance drift. In this report, an adhesive gel electrode featuring an inkjet-printed poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) trace on a poly(vinyl alcohol) (PVA) hydrogel substrate with a methyl cellulose adhesive is presented. When attached to the inside of a Venus flytrap (Dionaea muscipula) lobe these biocompatible printed conformable electrodes demonstrate long-term mechanical stability and reliable continuous recording of action potentials, including when removed and reattached over 14 days. Compared to rigid Ag/AgCl electrodes, these bioelectrodes provide higher sensitivity, faster signal dynamics, and comparable signal-to-noise ratios. The gel electrodes maintain low impedance over extended periods (120 hrs), which is critical for long-term monitoring of bioelectronic signals. This stability enabled real-time monitoring of a Venus flytrap’s response to environmental factors such as temperature variations, insect activity, and diurnal variations. Additionally, the bioelectrodes were integrated with low-cost ESP32 microcontroller-based electronics, enabling wireless plant-to-plant communication over long distances. This system demonstrates a biologically integrated platform for developing nature-integrated networks that utilize living plants as sensor nodes.

Xanthophylls are carotenoids with diverse roles in stress protection across all taxa of life. This review highlights chloroplast-localized xanthophylls (with a focus on zeaxanthin) of plants by presenting an overview of the protective effects of xanthophylls as well as the role of carotenoids as precursors of multiple plant stress hormones. It also examines the roles of xanthophylls and stress hormones in signaling cascades between the chloroplast and nuclear genes that control plant growth, development, and stress defenses. This overview addresses the biosynthetic pathways of xanthophylls and carotenoid-derived plant stress hormones, functions of xanthophylls in photoprotection of photosynthesis, carotenoids as essential human micronutrients, and roles of xanthophylls in membrane integrity. Attention is given to the involvement of zeaxanthin in both abiotic and biotic defense as well as its impact on components of the biotic defense system with contrasting targets. Examples for the multiple principal loops of signaling cascades between the chloroplast and nucleus, which are based on chloroplast redox state and modulated by xanthophylls, are summarized. This review integrates the role of chloroplast carotenoids in controlling light-use efficiency and providing photoprotection with their system-wide regulatory effects as precursors of carotenoid-derived plant stress hormones and modulators of chloroplast redox state. A better understanding of these connections is needed to guide development of plant lines with improved resilience and productivity in complex, changing, and challenging environments.

Photosynthetica covers wide range of photosynthesis research or research including photosynthetic parameters of both experimental and theoretical nature.

Atmospheric carbon dioxide (CO₂) is projected to be twice as high as the pre-industrial level by 2050. This review briefly highlights key responses of terrestrial plants to elevated CO₂ and compares these with the responses of aquatic floating plants of the family Lemnaceae (duckweeds). Duckweeds are efficient at removing CO₂ from the atmosphere, which we discuss in the context of their exceptionally high growth rates and capacity for starch storage in green tissue. In contrast to cultivation of terrestrial crops, duckweeds do not contribute to CO₂ release from soils. We briefly review how this potential for contributions to stabilizing atmospheric CO₂ levels is paired with multiple additional applications and services of duckweeds. These additional roles include wastewater phytoremediation, feedstock for biofuel production, and superior nutritional quality (for humans and livestock), while requiring minimal space and input of light and fertilizer. We, furthermore, elaborate on other environmental factors, such as nutrient availability, light supply, and the presence of a microbiome, that impact the response of duckweed to elevated CO₂. Under a combination of elevated CO₂ with low nutrient availability and moderate light supply, duckweeds’ microbiome helps maintain CO₂ sequestration and relative growth rate. When incident light intensity increases (in the presence of elevated CO₂), the microbiome minimizes negative feedback on photosynthesis from increased sugar accumulation. In addition, duckweed shows a clear propensity for absorption of ammonium over nitrate, accepting ammonium from their endogenous N₂-fixing Rhizobium symbionts, and production of large amounts of vegetative storage protein. Finally, cultivation of duckweed could be further optimized using hydroponic vertical farms where nutrients and water are recirculated, saving both resources, space, and energy to produce high-value products.

Arabidopsis thaliana ecotypes adapted to native habitats with different daylengths, temperatures, and precipitation were grown experimentally under seven combinations of light intensity and leaf temperature to assess their acclimatory phenotypic plasticity in foliar structure and function. There were no differences among ecotypes when plants developed under moderate conditions of 400 µmol photons m⁻² s⁻¹ and 25 °C. However, in response to more extreme light or temperature regimes, ecotypes that evolved in habitats with pronounced differences in either the magnitude of changes in daylength or temperature or in precipitation level exhibited pronounced adjustments in photosynthesis and transpiration, as well as anatomical traits supporting these functions. Specifically, when grown under extremes of light intensity (100 versus 1000 µmol photons m⁻² s⁻¹) or temperature (8 °C versus 35 °C), ecotypes from sites with the greatest range of daylengths and temperature over the growing season exhibited the greatest differences in functional and structural features related to photosynthesis (light- and CO₂-saturated capacity of oxygen evolution, leaf dry mass per area or thickness, phloem cells per minor vein, and water-use efficiency of CO₂ uptake). On the other hand, the ecotype from the habitat with the lowest precipitation showed the greatest plasticity in features related to water transport and loss (vein density, ratio of water to sugar conduits in foliar minor veins, and transpiration rate). Despite these differences, common structure–function relationships existed across all ecotypes and growth conditions, with significant positive, linear correlations (i) between photosynthetic capacity (ranging from 10 to 110 µmol O₂ m⁻² s⁻¹) and leaf dry mass per area (from 10 to 75 g m⁻²), leaf thickness (from 170 to 500 µm), and carbohydrate-export infrastructure (from 6 to 14 sieve elements per minor vein, from 2.5 to 8 µm² cross-sectional area per sieve element, and from 16 to 82 µm² cross-sectional area of sieve elements per minor vein); (ii) between transpiration rate (from 1 to 17 mmol H₂O m⁻² s⁻¹) and water-transport infrastructure (from 3.5 to 8 tracheary elements per minor vein, from 13.5 to 28 µm² cross-sectional area per tracheary element, and from 55 to 200 µm² cross-sectional area of tracheary elements per minor vein); (iii) between the ratio of transpirational water loss to CO₂ fixation (from 0.2 to 0.7 mol H₂O to mmol⁻¹ CO₂) and the ratio of water to sugar conduits in minor veins (from 0.4 to 1.1 tracheary to sieve elements, from 4 to 6 µm² cross-sectional area of tracheary to sieve elements, and from 2 to 6 µm² cross-sectional area of tracheary elements to sieve elements per minor vein); (iv) between sugar conduits and sugar-loading cells; and (v) between water conducting and sugar conducting cells. Additionally, the proportion of water conduits to sugar conduits was greater for all ecotypes grown experimentally under warm-to-hot versus cold temperature. Thus, developmental acclimation to the growth environment included ecotype-dependent foliar structural and functional adjustments resulting in multiple common structural and functional relationships.

The ability of plants to respond to environmental fluctuations is supported by acclimatory adjustments in plant form and function that may require several days and development of a new leaf. We review adjustments in photosynthetic, photoprotective, and foliar vascular capacity in response to variation in light and temperature in terrestrial plants. The requirement for extensive acclimation to these environmental conditions in terrestrial plants is contrasted with an apparent lesser need for acclimation to different light environments, including rapid light fluctuations, in floating aquatic plants for the duckweed Lemna minor. Relevant features of L. minor include unusually high growth rates and photosynthetic capacities coupled with the ability to produce high levels of photoprotective xanthophylls across a wide range of growth light environments without compromising photosynthetic efficiency. These features also allow L. minor to maximize productivity and avoid problems during an abrupt experimental transfer of low-light-grown plants to high light. The contrasting responses of land plants and floating aquatic plants to the light environment further emphasize the need of land plants to, e.g., experience light fluctuations in their growth environment before they induce acclimatory adjustments that allow them to take full advantage of natural settings with such fluctuations.

Rising atmospheric carbon dioxide (CO₂) levels can impact plant photosynthesis and productivity and threaten food security, especially when combined with additional environmental stressors. This study addresses the effects of elevated CO₂ in combination with low nutrient supply on Lemna minor (common duckweed). We quantified plant growth rate and nutritional quality (protein content) and evaluated whether any adverse effects of elevated CO₂, low nutrients, or the combination of the two could be mitigated by plant-microbe interaction. Plants were grown under controlled conditions and were either uninoculated or inoculated with microorganisms from a local pond that supported L. minor populations. Under low nutrients in combination with high CO₂, growth (plant area expansion rate) decreased and biomass accumulation increased, albeit with lower nutritional quality (lower percentage of protein per plant biomass). Inoculation with plant-associated microorganisms restored area expansion rate and further stimulated biomass accumulation while supporting a high protein-to-biomass ratio and, thus, a high nutritional quality. These findings indicate that plant-microbe interaction can support a higher nutritional quality of plant biomass under elevated atmospheric CO₂ levels, an important finding for both human and non-human consumers during a time of rapid environmental change.

Development of a nutritious, sustainable food source is essential to address worldwide deficiencies in human micronutrients. Aquatic floating plants (e.g., species in the family Lemnaceae, duckweeds) are uniquely suited for area-efficient productivity with exceptionally high rates of growth and nutritional quality. Here, we provide an overview of the role of dietary micronutrients (with a focus on carotenoids) in human health and the promise of Lemnaceae as sustainable crops. We examine the effect of growth light environment on plant biomass production and levels of the carotenoids zeaxanthin, lutein, and pro-vitamin A (β-carotene), as well as the antioxidant vitamin E (α-tocopherol), and protein. Data on each of these nutrients are reported on a plant dry biomass basis (as relevant for nutrition) as well as relative to the required input of light energy (as relevant to resource-use efficiency).