Improved monitoring of cryptogam gas-exchange and volatile emissions during desiccation-rehydration cycles with a within-chamber hydration method.

Desiccation-rehydration studies in cryptogams constitute an important tool to understand the relation of key physiological traits with species stress tolerance and environmental adaptability. Real-time monitoring of responses has been limited by the design of commercial or custom measuring cuvettes and difficulties in experimental manipulation. We developed a within-chamber rehydration method that allows to rewater the samples rapidly, without the need to open the chamber and take out the sample for manual rehydration by the investigator.

Impacts of methyl jasmonate on Selaginella martensii: volatiles, transcriptomics, phytohormones, and gas exchange.

Methyl jasmonate (MeJA) induces various defence responses in seed plants, but for early plant lineages, information on the potential of jasmonates to elicit stress signalling and trigger physiological modifications is limited. The spikemoss Selaginella martensii was exposed to a range of MeJA concentrations (0, 10, 25, and 50 mM), and biogenic volatile organic compound (BVOC) emissions, photosynthetic rate (A), and stomatal conductance (gs) were continuously measured. In addition, changes in phytohormone concentrations and gene expression were studied.

Impacts of Dutch elm disease-causing fungi on foliage photosynthetic characteristics and volatiles in Ulmus species with different pathogen resistance.

Global warming affects the abiotic and biotic growth environment of plants, including the spread of fungal diseases such as Dutch elm disease (DED). Dutch elm disease-resistance of different Ulmus species varies, but how this is reflected in leaf-level physiological pathogen responses has not been investigated. We studied the impacts of mechanical injury alone and mechanical injury plus inoculation with the DED-causing pathogens Ophiostoma novo-ulmi subsp.

CO -responsiveness of leaf isoprene emission: Why do species differ?

Leaf isoprene emission rate, I, decreases with increasing atmospheric CO concentration with major implications for global change. There is a significant interspecific variability in [CO ]-responsiveness of I, but the extent of this variation is unknown and its reasons are not understood. We hypothesized that the magnitude of emission reduction reflects the size and changeability of precursor pools responsible for isoprene emission (dimethylallyl diphosphate, DMADP and 2-methyl-erythritol 2,4-cyclodiphosphate, MEcDP).

Combined Acute Ozone and Water Stress Alters the Quantitative Relationships between O Uptake, Photosynthetic Characteristics and Volatile Emissions in .

Ozone (O) entry into plant leaves depends on atmospheric O concentration, exposure time and openness of stomata. O negatively impacts photosynthesis rate () and might induce the release of reactive volatile organic compounds (VOCs) that can quench O, and thereby partly ameliorate O stress. Water stress reduces stomatal conductance () and O uptake and can affect VOC release and O quenching by VOC, but the interactive effects of O exposure and water stress, as possibly mediated by VOC, are poorly understood.

Wounding-Induced VOC Emissions in Five Tropical Agricultural Species.

Leaf mechanical wounding triggers a rapid release-within minutes-of a blend of volatile organic compounds. A wounding-induced VOC blend is mainly composed of oxygenated ubiquitous stress volatiles such as methanol and volatile products of lipoxygenase (LOX) pathway (mainly C5 and C6 alcohols and aldehydes and their derivatives), but also includes multiple minor VOCs that collectively act as infochemicals, inducing defences in non-damaged plant leaves and neighbouring plants and attracting herbivore enemies. At present, the interspecific variability of the rate of induction and magnitude of wounding-induced emissions and the extent to which plant structural traits and physiological activity alter these emissions are poorly known.

Are stomata in ferns and allies sluggish? Stomatal responses to CO , humidity and light and their scaling with size and density.

Fast stomatal reactions enable plants to successfully cope with a constantly changing environment yet there is an ongoing debate on the stomatal regulation mechanisms in basal plant groups. We measured stomatal morphological parameters in 29 fern and allied species from temperate to tropical biomes and two outgroup angiosperm species. Stomatal dynamic responses to environmental drivers were measured in 16 ferns and the two angiosperms using a gas-exchange system.

Lethal heat stress-dependent volatile emissions from tobacco leaves: what happens beyond the thermal edge?

Natural vegetation is predicted to suffer from extreme heat events as a result of global warming. In this study, we focused on the immediate response to heat stress. Photosynthesis and volatile emissions were measured in the leaves of tobacco (Nicotiana tabacum cv.

A novel approach for real-time monitoring of leaf wounding responses demonstrates unprecedently fast and high emissions of volatiles from cut leaves.

Wounding is a key plant stress that results in a rapid, within seconds to a few minutes, release of ubiquitous stress volatiles and stored volatiles in species with storage structures. Understanding the timing and extent of wound-dependent volatile elicitation is needed to gain an insight into different emission controls, but real-time monitoring of plant emissions through wounding treatments has been hampered by the need to stop the measurements to perform the wounding, slow stabilization of gas flows upon chamber closure and smearing out the signal by large chambers and long sampling lines. We developed a novel leaf cutter that allows to rapidly perform highly precise leaf cuts within the leaf chamber.

Evidence That Isoprene Emission Is Not Limited by Cytosolic Metabolites. Exogenous Malate Does Not Invert the Reverse Sensitivity of Isoprene Emission to High [CO].

Isoprene is synthesized via the chloroplastic 2--methyl-d-erythritol 4-phosphate/1-deoxy-d-xylulose 5-phosphate pathway (MEP/DOXP), and its synthesis is directly related to photosynthesis, except under high CO concentration, when the rate of photosynthesis increases but isoprene emission decreases. Suppression of MEP/DOXP pathway activity by high CO has been explained either by limited supply of the cytosolic substrate precursor, phosphopyruvate (PEP), into chloroplast as the result of enhanced activity of cytosolic PEP carboxylase or by limited supply of energetic and reductive equivalents. We tested the PEP-limitation hypotheses by feeding leaves with the PEP carboxylase competitive inhibitors malate and diethyl oxalacetate (DOA) in the strong isoprene emitter hybrid aspen ( × ).

Spectacular Oscillations in Plant Isoprene Emission under Transient Conditions Explain the Enigmatic CO2 Response.

Plant isoprene emissions respond to light and temperature similarly to photosynthesis, but CO dependencies of isoprene emission and photosynthesis are profoundly different, with photosynthesis increasing and isoprene emission decreasing with increasing CO concentration due to reasons not yet understood. We studied isoprene emission, net assimilation rate, and chlorophyll fluorescence under different CO and O concentrations in the strong isoprene emitter hybrid aspen (Populus tremula × Populus tremuloides), and used rapid changes in ambient CO or O concentrations or light level to induce oscillations. As isoprene-emitting species support very high steady-state chloroplastic pool sizes of the primary isoprene substrate, dimethylallyl diphosphate (DMADP), which can mask the effects of oscillatory dynamics on isoprene emission, the size of the DMADP pool was experimentally reduced by either partial inhibition of isoprenoid synthesis pathway by fosmidomycin-feeding or by changes in ambient gas concentrations leading to DMADP pool depletion in intact leaves.

How specialized volatiles respond to chronic and short-term physiological and shock heat stress in Brassica nigra.

Brassicales release volatile glucosinolate breakdown products upon tissue mechanical damage, but it is unclear how the release of glucosinolate volatiles responds to abiotic stresses such as heat stress. We used three different heat treatments, simulating different dynamic temperature conditions in the field to gain insight into stress-dependent changes in volatile blends and photosynthetic characteristics in the annual herb Brassica nigra (L.) Koch.

Emission Timetable and Quantitative Patterns of Wound-Induced Volatiles Across Different Leaf Damage Treatments in Aspen (Populus Tremula).

Plant-feeding herbivores can generate complex patterns of foliar wounding, but it is unclear how wounding-elicited volatile emissions scale with the severity of different wounding types, and there is no common protocol for wounding experiments. We investigated the rapid initial response to wounding damage generated by different numbers of straight cuts and punctures through leaf lamina as well as varying area of lamina squeezing in the temperate deciduous tree Populus tremula. Wounding-induced volatile emission time-courses were continuously recorded by a proton-transfer-reaction time-of-flight mass-spectrometer.

The photosynthetic capacity in 35 ferns and fern allies: mesophyll CO2 diffusion as a key trait.

Ferns and fern allies have low photosynthetic rates compared with seed plants. Their photosynthesis is thought to be limited principally by physical CO2 diffusion from the atmosphere to chloroplasts. The aim of this study was to understand the reasons for low photosynthesis in species of ferns and fern allies (Lycopodiopsida and Polypodiopsida).

Controls of the quantum yield and saturation light of isoprene emission in different-aged aspen leaves.

Leaf age alters the balance between the use of end-product of plastidic isoprenoid synthesis pathway, dimethylallyl diphosphate (DMADP), in prenyltransferase reactions leading to synthesis of pigments of photosynthetic machinery and in isoprene synthesis, but the implications of such changes on environmental responses of isoprene emission have not been studied. Because under light-limited conditions, isoprene emission rate is controlled by DMADP pool size (SDMADP ), shifts in the share of different processes are expected to particularly strongly alter the light dependency of isoprene emission. We examined light responses of isoprene emission in young fully expanded, mature and old non-senescent leaves of hybrid aspen (Populus tremula x P.

Bisphosphonate inhibitors reveal a large elasticity of plastidic isoprenoid synthesis pathway in isoprene-emitting hybrid aspen.

Recently, a feedback inhibition of the chloroplastic 1-deoxy-D-xylulose 5-phosphate (DXP)/2-C-methyl-D-erythritol 4-phosphate (MEP) pathway of isoprenoid synthesis by end products dimethylallyl diphosphate (DMADP) and isopentenyl diphosphate (IDP) was postulated, but the extent to which DMADP and IDP can build up is not known. We used bisphosphonate inhibitors, alendronate and zoledronate, that inhibit the consumption of DMADP and IDP by prenyltransferases to gain insight into the extent of end product accumulation and possible feedback inhibition in isoprene-emitting hybrid aspen (Populus tremula × Populus tremuloides). A kinetic method based on dark release of isoprene emission at the expense of substrate pools accumulated in light was used to estimate the in vivo pool sizes of DMADP and upstream metabolites.

Fast cyclic electron transport around photosystem I in leaves under far-red light: a proton-uncoupled pathway?

Fast cyclic electron transport (CET) around photosystem I (PS I) was observed in sunflower (Helianthus annuus L.) leaves under intense far-red light (FRL) of up to 200 mumol quanta m(-2) s(-1). The electron transport rate (ETR) through PS I was found from the FRL-dark transmittance change at 810 and 950 nm, which was deconvoluted into redox states and pool sizes of P700, plastocyanin (PC) and cytochrome f (Cyt f).

Rates and roles of cyclic and alternative electron flow in potato leaves.

Measurements of 810 nm transmittance changes in leaves, simultaneously with Chl fluorescence, CO(2) uptake and O(2) evolution, were carried out on potato (Solanum tuberosum L.) leaves with altered expression of plastidic NADP-dependent malate dehydrogenase. Electron transport rates were calculated: J(C) from the CO(2) uptake rate considering ribulose-1,5-bisphosphate (RuBP) carboxylation and oxygenation, J(O) from the O(2) evolution rate, J(F) from Chl fluorescence parameters and J(I) from the post-illumination re-reduction speed of PSI donors.

Dark inactivation of ferredoxin-NADP reductase and cyclic electron flow under far-red light in sunflower leaves.

The oxidation kinetics under far-red light (FRL) of photosystem I (PSI) high potential donors P700, plastocyanin (PC), and cytochrome f (Cyt f) were investigated in sunflower leaves with the help of a new high-sensitivity photometer at 810 nm. The slopes of the 810 nm signal were measured immediately before and after FRL was turned on or off. The same derivatives (slopes) were calculated from a mathematical model based on redox equilibrium between P700, PC and Cyt f and the parameters of the model were varied to fit the model to the measurements.