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.

Tomato in the spotlight: Light regulation of whole-plant physiology in tomato.

The introduction of LED light in plant research and controlled environment agriculture has given a boost to understanding how light regulates tomato physiology. This paper reviews the regulation of whole-plant physiological processes in tomato by light. Emphasis is on morphogenesis, light interception, photosynthesis, source/sink interactions, assimilate partitioning, fruit set, fruit development, plant-water relations and how this controls plant growth and fruit quality.

Beyond the boundary: a new road to improve photosynthesis by wind.

Plants interact with their microclimate, simultaneously responding to and influencing it. A key element in this interaction is the leaf boundary layer: a stagnant air layer enveloping the leaf, creating a resistance to heat and gas exchange. Its thickness, altered mainly by airflow and leaf morphology, determines the leaf-to-air interaction.

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.

Fast stomatal kinetics in sorghum enable tight coordination with photosynthetic responses to dynamic light intensity and safeguard high water use efficiency.

In this study, we assessed 43 accessions of sorghum from 16 countries across three continents. Our objective was to identify stomatal and photosynthetic traits that could be exploited in breeding programmes to increase photosynthesis without increasing water use under dynamic light environments. Under field conditions, sorghum crops often have limited water availability and are exposed to rapidly fluctuating light intensities, which influences both photosynthesis and stomatal behaviour.

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.

Imaging Spatial and Temporal Variation in Photosynthesis Using Chlorophyll Fluorescence.

Chlorophyll fluorescence imaging provides a noninvasive rapid screen to assess the physiological status of a number of leaves or plants simultaneously. Although there are no standard protocols for chlorophyll fluorescence imaging, here we provide an example of routines for some of the typical measurements.

A guide to photosynthetic gas exchange measurements: Fundamental principles, best practice and potential pitfalls.

Gas exchange measurements enable mechanistic insights into the processes that underpin carbon and water fluxes in plant leaves which in turn inform understanding of related processes at a range of scales from individual cells to entire ecosytems. Given the importance of photosynthesis for the global climate discussion it is important to (a) foster a basic understanding of the fundamental principles underpinning the experimental methods used by the broad community, and (b) ensure best practice and correct data interpretation within the research community. In this review, we outline the biochemical and biophysical parameters of photosynthesis that can be investigated with gas exchange measurements and we provide step-by-step guidance on how to reliably measure them.

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 ().

Development of an accurate low cost NDVI imaging system for assessing plant health.

Background: Spectral imaging is a key method for high throughput phenotyping that can be related to a large variety of biological parameters. The Normalised Difference Vegetation Index (NDVI), uses specific wavelengths to compare crop health and performance. Increasing the accessibility of spectral imaging systems through the development of small, low cost, and easy to use platforms will generalise its use for precision agriculture.

The impact of growth at elevated [CO2] on stomatal anatomy and behavior differs between wheat species and cultivars.

The ability of plants to respond to changes in the environment is crucial to their survival and reproductive success. The impact of increasing the atmospheric CO2 concentration (a[CO2]), mediated by behavioral and developmental responses of stomata, on crop performance remains a concern under all climate change scenarios, with potential impacts on future food security. To identify possible beneficial traits that could be exploited for future breeding, phenotypic variation in morphological traits including stomatal size and density, as well as physiological responses and, critically, the effect of growth [CO2] on these traits, was assessed in six wheat relative accessions (including Aegilops tauschii, Triticum turgidum ssp.

Stomata on the abaxial and adaxial leaf surfaces contribute differently to leaf gas exchange and photosynthesis in wheat.

Although stomata are typically found in greater numbers on the abaxial surface, wheat flag leaves have greater densities on the adaxial surface. We determine the impact of this less common stomatal patterning on gaseous fluxes using a novel chamber that simultaneously measures both leaf surfaces. Using a combination of differential illuminations and CO concentrations at each leaf surface, we found that mesophyll cells associated with the adaxial leaf surface have a higher photosynthetic capacity than those associated with the abaxial leaf surface, which is supported by an increased stomatal conductance (driven by differences in stomatal density).

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.

Light, power, action! Interaction of respiratory energy- and blue light-induced stomatal movements.

Although the signalling pathway of blue light (BL)-dependent stomatal opening is well characterized, little is known about the interspecific diversity, the role it plays in the regulation of gas exchange and the source of energy used to drive the commonly observed increase in pore aperture. Using a combination of red and BL under ambient and low [O ] (to inhibit respiration), the interaction between BL, photosynthesis and respiration in determining stomatal conductance was investigated. These findings were used to develop a novel model to predict the feedback between photosynthesis and stomatal conductance under these conditions.

Variation in key leaf photosynthetic traits across wheat wild relatives is accession dependent not species dependent.

The wild relatives of modern wheat represent an underutilized source of genetic and phenotypic diversity and are of interest in breeding owing to their wide adaptation to diverse environments. Leaf photosynthetic traits underpin the rate of production of biomass and yield and have not been systematically explored in the wheat relatives. This paper identifies and quantifies the phenotypic variation in photosynthetic, stomatal, and morphological traits in up to 88 wheat wild relative accessions across five genera.

Stimulating photosynthetic processes increases productivity and water-use efficiency in the field.

Previous studies have demonstrated that the independent stimulation of either electron transport or RuBP regeneration can increase the rate of photosynthetic carbon assimilation and plant biomass. In this paper, we present evidence that a multigene approach to simultaneously manipulate these two processes provides a further stimulation of photosynthesis. We report on the introduction of the cyanobacterial bifunctional enzyme fructose-1,6-bisphosphatase/sedoheptulose-1,7-bisphosphatase or the overexpression of the plant enzyme sedoheptulose-1,7-bisphosphatase, together with the expression of the red algal protein cytochrome c, and show that a further increase in biomass accumulation under both glasshouse and field conditions can be achieved.

Guard Cell Starch Degradation Yields Glucose for Rapid Stomatal Opening in Arabidopsis.

Starch in Arabidopsis () guard cells is rapidly degraded at the start of the day by the glucan hydrolases α-AMYLASE3 (AMY3) and β-AMYLASE1 (BAM1) to promote stomatal opening. This process is activated via phototropin-mediated blue light signaling downstream of the plasma membrane H-ATPase. It remains unknown how guard cell starch degradation integrates with light-regulated membrane transport processes in the fine control of stomatal opening kinetics.

Thermography methods to assess stomatal behaviour in a dynamic environment.

Although thermography allows rapid, non-invasive measurements of large numbers of plants, it has not been used extensively due to the difficulty in deriving biologically relevant information such as leaf transpiration (E) and stomatal conductance (gsw) from thermograms. Methods normalizing leaf temperature using temperatures from reference materials (e.g.

Role of blue and red light in stomatal dynamic behaviour.

Plants experience changes in light intensity and quality due to variations in solar angle and shading from clouds and overlapping leaves. Stomatal opening to increasing irradiance is often an order of magnitude slower than photosynthetic responses, which can result in CO2 diffusional limitations on leaf photosynthesis, as well as unnecessary water loss when stomata continue to open after photosynthesis has reached saturation. Stomatal opening to light is driven by two distinct pathways; the 'red' or photosynthetic response that occurs at high fluence rates and saturates with photosynthesis, and is thought to be the main mechanism that coordinates stomatal behaviour with photosynthesis; and the guard cell-specific 'blue' light response that saturates at low fluence rates, and is often considered independent of photosynthesis, and important for early morning stomatal opening.

Dynamic leaf energy balance: deriving stomatal conductance from thermal imaging in a dynamic environment.

In spite of the significant progress made in recent years, the use of thermography to derive biologically relevant traits remains a challenge under fluctuating conditions. The aim of this study was to rethink the current method to process thermograms and derive temporal responses of stomatal conductance (gsw) using dynamic energy balance equations. Time-series thermograms provided the basis for a spatial and temporal characterization of gsw responses in wheat (Triticum aestivum).