DynG: a dynamic scaling factor for thermographic stomatal conductance estimation under changing environmental conditions.

Thermal imaging is a key plant phenotyping and monitoring technique but faces major bottlenecks in accurately and efficiently inferring stomatal conductance (g) from leaf temperature. The conductance index (I) was previously proposed to estimate g from thermography by linking temperature differences between real and artificial leaves (ALs) based on the leaf energy balance. However, I is highly sensitive to environmental fluctuations, hampering interpretation and reducing reproducibility.

Elevated [CO] Affected Fluctuating Light Acclimation in Cucumber Plants by Changes in Specific Leaf Area and Photosynthetic Efficiency.

Plants continuously acclimate to natural fluctuations in light intensity, and this may be modulated by elevated CO (e[CO]) concentrations. How strongly such a combination affects plant and leaf morphology, anatomy, and photosynthetic biochemistry is unknown. We grew cucumber (Cucumis sativus) under sinusoidal (SN) and randomly fluctuating light (FL) intensities, at two CO levels (440 μmol mol, a[CO]; 860 μmol mol, e[CO]), and conducted an extensive analysis of photosynthesis, leaf anatomy, plant morphology, and biomass.

Frequency of light fluctuations affects tomato morphology and physiology only at extreme amplitudes.

Introduction: Electricity prices can fluctuate considerably during the day due to the dependency of solar and wind energy and varying demands. Fluctuating lighting regimes might thus be economically attractive. However, only limited knowledge is available on how plants grow under fluctuating light conditions.

Viewing Stomata in Action: Autonomous in Planta Imaging of Individual Stomatal Movement.

Stomata regulate plant gas exchange under changing environments, but observations of single stomata dynamics in planta are sparse. We developed a compact microscope system that can measure the kinetics of tens of stomata in planta simultaneously, with sub-minute time resolution. Darkfield imaging with green light was used to create 3D stacks from which 2D surface projections were constructed to resolve stomatal apertures.

A simple new method to determine leaf specific heat capacity.

Background: Quantifying plant transpiration via thermal imaging is desirable for applications in agriculture, plant breeding, and plant science. However, thermal imaging under natural non-steady state conditions is currently limited by the difficulty of quantifying thermal properties of leaves, especially specific heat capacity (C). Existing literature offers only rough estimates of C and lacks simple and accurate methods to determine it.

Leaf Photosynthetic and Photoprotective Acclimation in the Ultraviolet-A1 and Blue Light Regions Follow a Continuous, Shallow Gradient.

Although blue light is known to produce leaves with high photosynthetic capacity, the role of the blue-adjacent UV-A1 (350-400 nm) in driving leaf photosynthetic acclimation is less studied. Tomato plants were grown under hybrid red and blue (RB; 95/5 μmol m s), as well as four treatments in which RB was supplemented with 50 μmol m s peaking at 365, 385, 410 and 450 nm, respectively. Acclimation to 365-450 nm led to a shallow gradient increase in trait values (i.

Quantifying the Photosynthetic Quantum Yield of Ultraviolet-A1 Radiation.

Although it powers photosynthesis, ultraviolet-A1 radiation (UV-A1) is usually not defined as photosynthetically active radiation (PAR). However, the quantum yield (QY) with which UV-A1 drives net photosynthesis rate (A) is unknown, as are the kinetics of A and chlorophyll fluorescence under constant UV-A1 exposure. We measured A in leaves of six genotypes at four spectra peaking at 365, 385, 410 and 450 nm, at intensities spanning 0-300 μmol m s.

Photosynthesis and photoprotection in top leaves respond faster to irradiance fluctuations than bottom leaves in a tomato canopy.

Accounting for the dynamic responses of photosynthesis and photoprotection to naturally fluctuating irradiance can improve predictions of plant performance in the field, but the variation of these dynamics within crop canopies is poorly understood. We conducted a detailed study of dynamic and steady-state photosynthesis, photoprotection, leaf pigmentation, and stomatal anatomy in four leaf layers (100, 150, 200, and 250 cm from the floor) of a fully grown tomato (Solanum lycopersicum cv. Foundation) canopy in a greenhouse.

Biochemical versus stomatal acclimation of dynamic photosynthetic gas exchange to elevated CO in three horticultural species with contrasting stomatal morphology.

Understanding photosynthetic acclimation to elevated CO (eCO) is important for predicting plant physiology and optimizing management decisions under global climate change, but is underexplored in important horticultural crops. We grew three crops differing in stomatal density-namely chrysanthemum, tomato, and cucumber-at near-ambient CO (450 μmol mol) and eCO (900 μmol mol) for 6 weeks. Steady-state and dynamic photosynthetic and stomatal conductance (g) responses were quantified by gas exchange measurements.

The role of red and white light in optimizing growth and accumulation of plant specialized metabolites at two light intensities in medical cannabis ( L.).

The cultivation of medical cannabis ( L.) is expanding in controlled environments, driven by evolving governmental regulations for healthcare supply. Increasing inflorescence weight and plant specialized metabolite (PSM) concentrations is critical, alongside maintaining product consistency.

Green light is similarly effective in promoting plant biomass as red/blue light: a meta-analysis.

Whether green light promotes or represses plant growth is an unresolved but important question, warranting a global meta-analysis of published data. We collected 136 datasets from 48 publications on 17 crop species, and calculated the green light effect for a range of plant traits. For each trait the effect was calculated as the ratio between the trait value attained under a red/blue background light plus green, divided by the value attained under the background light only, both having the same light intensity.

Short-term salt stress reduces photosynthetic oscillations under triose phosphate utilization limitation in tomato.

Triose phosphate utilization (TPU) limitation is one of the three biochemical limitations of photosynthetic CO2 assimilation rate in C3 plants. Under TPU limitation, abrupt and large transitions in light intensity cause damped oscillations in photosynthesis. When plants are salt-stressed, photosynthesis is often down-regulated particularly under dynamic light intensity, but how salt stress affects TPU-related dynamic photosynthesis is still unknown.

Petunia as a model for MYB transcription factor action under salt stress.

Salinity is a current and growing problem, affecting crops worldwide by reducing yields and product quality. Plants have different mechanisms to adapt to salinity; some crops are highly studied, and their salinity tolerance mechanisms are widely known. However, there are other crops with commercial importance that still need characterization of their molecular mechanisms.

Rapid spatial assessment of leaf-absorbed irradiance.

Image-based high-throughput phenotyping promises the rapid determination of functional traits in large plant populations. However, interpretation of some traits - such as those related to photosynthesis or transpiration rates - is only meaningful if the irradiance absorbed by the measured leaves is known, which can differ greatly between different parts of the same plant and within canopies. No feasible method currently exists to rapidly measure absorbed irradiance in three-dimensional plants and canopies.

Diurnal decline in photosynthesis and stomatal conductance in several tropical species.

Photosynthesis () and stomatal conductance () change diurnally due to internal signals, but the effects of diurnal rhythms on dynamic photosynthetic behavior are understudied. We examined diurnal changes in and in ten tropical species: across species, there was a tendency for and to decline diurnally when these were repeatedly measured under either steady-state or fluctuating irradiance conditions. We then examined in more detail the irradiance-induced kinetics of gas exchange in a C and C crop species each, namely fig () and sugarcane ().

A small dynamic leaf-level model predicting photosynthesis in greenhouse tomatoes.

The conversion of supplemental greenhouse light energy into biomass is not always optimal. Recent trends in global energy prices and discussions on climate change highlight the need to reduce our energy footprint associated with the use of supplemental light in greenhouse crop production. This can be achieved by implementing "smart" lighting regimens which in turn rely on a good understanding of how fluctuating light influences photosynthetic physiology.

A simple system for phenotyping of plant transpiration and stomatal conductance response to drought.

Plant breeding for increased crop water use efficiency or drought stress resistance requires methods to quickly assess the transpiration rate (E) and stomatal conductance (g) of a large number of individual plants. Several methods to measure E and g exist, each of which has its own advantages and shortcomings. To add to this toolbox, we developed a method that uses whole-plant thermal imaging in a controlled environment, where aerial humidity is changed rapidly to induce changes in E that are reflected in changes in leaf temperature.

Light acclimation interacts with thylakoid ion transport to govern the dynamics of photosynthesis in Arabidopsis.

Understanding photosynthesis in natural, dynamic light environments requires knowledge of long-term acclimation, short-term responses, and their mechanistic interactions. To approach the latter, we systematically determined and characterized light-environmental effects on thylakoid ion transport-mediated short-term responses during light fluctuations. For this, Arabidopsis thaliana wild-type and mutants of the Cl channel VCCN1 and the K exchange antiporter KEA3 were grown under eight different light environments and characterized for photosynthesis-associated parameters and factors in steady state and during light fluctuations.

Ultrasound Pulse Emission Spectroscopy Method to Characterize Xylem Conduits in Plant Stems.

Although it is well known that plants emit acoustic pulses under drought stress, the exact origin of the waveform of these ultrasound pulses has remained elusive. Here, we present evidence for a correlation between the characteristics of the waveform of these pulses and the dimensions of xylem conduits in plants. Using a model that relates the resonant vibrations of a vessel to its dimension and viscoelasticity, we extract the xylem radii from the waveforms of ultrasound pulses and show that these are correlated and in good agreement with optical microscopy.

Variation of Photosynthetic Induction in Major Horticultural Crops Is Mostly Driven by Differences in Stomatal Traits.

Under natural conditions, irradiance frequently fluctuates, causing net photosynthesis rate () to respond slowly and reducing the yields. We quantified the genotypic variation of photosynthetic induction in 19 genotypes among the following six horticultural crops: basil, chrysanthemum, cucumber, lettuce, tomato, and rose. Kinetics of photosynthetic induction and the stomatal opening were measured by exposing shade-adapted leaves (50 μmol m s) to a high irradiance (1000 μmol m s) until reached a steady state.

NaCl affects photosynthetic and stomatal dynamics by osmotic effects and reduces photosynthetic capacity by ionic effects in tomato.

NaCl stress affects stomatal behavior and photosynthesis by a combination of osmotic and ionic components, but it is unknown how these components affect stomatal and photosynthetic dynamics. Tomato (Solanum lycopersicum) plants were grown in a reference nutrient solution [control; electrical conductivity (EC)=2.3 dS m-1], a solution containing additional macronutrients (osmotic effect; EC=12.

Acclimating Cucumber Plants to Blue Supplemental Light Promotes Growth in Full Sunlight.

Raising young plants is important for modern greenhouse production. Upon transfer from the raising to the production environment, young plants should maximize light use efficiency while minimizing deleterious effects associated with exposure to high light (HL) intensity. The light spectrum may be used to establish desired traits, but how plants acclimated to a given spectrum respond to HL intensity exposure is less well explored.

LED and HPS Supplementary Light Differentially Affect Gas Exchange in Tomato Leaves.

Using light emitting diodes (LED) instead of conventionally used high pressure sodium (HPS) lamps as a supplemental light source in greenhouses results in a higher efficacy (µmol light per J electricity) and makes it possible to customize the light spectrum. To explore the effects of LED and HPS on gas exchange, thermal relations, photosynthesis, and water status of young tomato plants, seven genotypes were grown in a greenhouse under LED (95% red, 5% blue) or HPS lamps in four experiments differing in the fraction of lamp light over natural light. HPS lights emit a broader spectrum of red (40%), green-yellow (50%), blue (5%), and far-red (5%) and a substantial amount of infrared radiation (heat).