Natural genetic variation in stomatal response can help to increase acclimation of plants to dried environments

In the current century, global warming is becoming an alarming issue causing an increase in the area of barren lands. Arid and semi-arid regions are characterised with shortage of water in both under- and above-ground environments. Plants with high water use efficiency should be considered for cultivation in those regions. Water loss is needed for cooling plant and absorbing minerals, however, excessive water loss can result in wilting. Plants control the water loss through adjusting the volume of stomatal guard cells and fine tuning the movements of stomata. Fine tune-functioning of stomata can help the plants to cope with drought conditions. Vapour pressure difference (VPD) between stomatal cavity and surrounding environment determines the water status of the leaf. In the short term, stomata respond in a regular way to VPD. However, when plants are exposed for a long term to conditions triggering stomatal opening (such as low VPD, prolonged lighting duration and air pollutants), the behaviour of the stomata in response to drought stress changes and the stomata are incapable of suitable response to closing stimuli (stomatal malfunctioning). Finding the reasons for occurrence of stomatal malfunctioning can help us to improve plant acclimation to dried environments. Exploring genetic variation in stomatal response among naturally occurring populations is the first step to figure out the mechanism controlling stomatal movements in different environments.</p

Greenhouse vapour pressure deficit and lighting conditions during growth can influence postharvest quality through the functioning of stomata

There is a tendency in horticulture to grow plants in greenhouses with high humidity and prolonged light periods, especially in winter. Although plants grow well in greenhouses with high relative humidity (RH) (low vapour pressure deficit; VPD), the plants produced under such greenhouse climates have limited control over water loss after harvest, leading to uncontrolled transpiration and decreased water content in the postharvest stage. This results in shortened vase-life of cut flowers and decreased quality of leafy vegetables. When plants had been produced in greenhouses with moderate humidity and natural day length, their stomata close when they are exposed to stomata closure-promoting environments (low RH, desiccation and darkness), as usually happens during the postharvest stage. However, in greenhouses with low VPD conditions and long photoperiods, stomata will not fully close during the postharvest stage; even decreased leaf water content will not result in full stomatal closure (stomatal malfunctioning) in products coming from those greenhouses. In this paper, greenhouse climate factors during the growth of plants that induce stomatal malfunctioning in the postharvest stage will be characterised. Approaches will be discussed to improve stomatal functionality under such greenhouse conditions in order to increase vase- and shelf-lives of products.</p

Effects of Ascorbic Acid and Reduced Glutathione on the Alleviation of Salinity Stress in Olive Plants

The aim of this study was to evaluate the effects of low molecular mass antioxidants and NaCl salinity on growth, ionic balance, proline, and water contents of ‘Zard’ olive trees under controlled greenhouse conditions. The experiment was carried out by spraying 2 mM of ascorbic acid (Asc) and 3 mM of reduced glutathione (GSH) on the plants that were treated with two salinity levels (0 and 100 mM NaCl) on their root medium. Plant growth parameters (leaf fresh weight, leaf dry weight, leaf number, total fresh weight, and total dry weight) were significantly improved by Asc compared with growth parameters in GSH and control plants. Higher concentrations of Na+ and Cl– were observed in salt-stressed plants, while Na+ and Cl– concentrations were decreased in the olive leaves that were sprayed with Asc. Salinity in the root zone caused a considerable decline in both K+ concentration and K/Na ratio. K+ concentration and K/Na ratio were significantly increased by application of Asc on plant leaves. Salinity caused an increase in electrolyte leakage (EL) compared with the control plants. Lowest EL and tissue water content (TWC) was obtained in Asc-sprayed plants, whereas TWC was increased in salt-stressed plants. Plants were subjected to salt stress and showed a higher relative water content (RWC) than the control plants. Salt stress induced proline accumulation in olive leaves. In conclusion, exogenous application of Asc is recommended to improve tolerance of olive plants under saline conditions

Growth, Biomass Partitioning, and Photosynthetic Performance of Chrysanthemum Cuttings in Response to Different Light Spectra

Chrysanthemum (Chrysanthemum morifolium) is among the most popular ornamental plants, propagated mainly through stem cuttings. There is a lack of information regarding the impact of the lighting environment on the successful production of cuttings and underlying mechanisms. The light spectrum affects plant morphology, growth, and photosynthesis. In the present study, chrysanthemum, cv. ‘Katinka’ cuttings, were exposed to five lighting spectra, including monochromatic red (R), blue (B) lights, and multichromatic lights, including a combination of R and B (R:B), a combination of R, B, and far red (R:B:FR) and white (W), for 30 days. B light enhanced areal growth, as indicated by a higher shoot mass ratio, while R light directed the biomass towards the underground parts of the cuttings. Monochromatic R and B lights promoted the emergence of new leaves. In contrast, individual leaf area was largest under multichromatic lights. Exposing the cuttings to R light led to the accumulation of carbohydrates in the leaves. Cuttings exposed to multichromatic lights showed higher chlorophyll content than monochromatic R- and B-exposed cuttings. Conversely, carotenoid and anthocyanin contents were the highest in monochromatic R- and B-exposed plants. B-exposed cuttings showed higher photosynthetic performance, exhibited by the highest performance index on the basis of light absorption, and maximal quantum yield of PSII efficiency. Although R light increased biomass toward roots, B light improved above-ground growth, photosynthetic functionality, and the visual performance of Chrysanthemum cuttings

Effects of Seed Priming with Gamma Radiation on Growth, Photosynthetic Functionality, and Essential Oil and Phytochemical Contents of Savory Plants

Gamma radiation has been suggested to have post-effects on emerging plants when applied to the seeds. In the present study, we aimed to induce alterations in photosynthetic functionality and subsequent modifications in secondary metabolites of summer savory following seed priming with gamma radiation. Savory seeds were treated with 0, 50, 100, 200, and 300 Gy gamma radiation in a completely randomized design with ten replications for morphological and photosynthetic parameters and three for phytochemical assessments. The results showed that gamma radiation on seeds adversely affected photosynthetic performance, especially at the highest doses. It negatively influenced the growth, while increasing the shoot branching, the number of nodes, and the diameter of the stem. Gamma radiation on seeds generally reduced pigmentation in savory leaves, such as chlorophylls, carotenoids, and anthocyanins. However, soluble sugar, starch, total phenolics, and total flavonoid contents were elevated in the leaves of plants that emerged from gamma-primed seeds. Gamma radiation priming reduced essential oil’s percentage and yield. Carvacrol and limonene components of essential oil were diminished, whereas linalool and thymol were increased. In conclusion, due to its inherent stress-inducing effects, and despite some positive effects on phytochemicals, seed priming with gamma radiation adversely influenced growth, photosynthesis, and quantity and quality of savory essential oils. Further research is still needed to target the use of gamma radiations before harvesting the seeds or determine the cytogenetic characteristics of irradiated plants

Effects of different light spectra on postharvest water relations of Anthurium under chilling conditions

Anthurium (Anthurium andraeanum L.) is a cold-sensitive species originating from the tropical region of the world. This plant is widely cultivated all around the globe for the beauty of its ornamental spathes. Here, the effect of light quality on water loss of cut anthurium flowers was tested under chilling conditions. Cut flowers of two anthurium cultivars, ‘Calore’ (red spathe) and ‘Angel’ (withe spathe), were exposed to a cold temperature (4°C) under different light spectra, including darkness (D), red (R), blue (B), 7:3 ratio of red:blue (RB), and white (W). The results showed that ‘Angel’ flowers under the B light spectrum had the lowest relative water content (RWC) and specific surface area. It also showed the lowest spathe water content on a dry weight basis. The lowest vase life was obtained for ‘Angel’ under the B light spectrum, while the longest vase life was obtained under the R light, for both studied cultivars. Under the B light treatment, more open stomata were observed. Accordingly, the highest water loss was observed in all treatments with the B light, and the lowest percentage of water loss was observed in the D and R light, especially in ‘Angel’ flowers. In conclusion, the B light spectrum negatively influences vase life of cut anthurium flowers, through its effect on water relations of the spathes.</p

Gamma-Aminobutyric Acid-Mediated Alkalinity Stress Alleviation in Lollo Rosso Lettuce under Diverse Light Spectra

The agricultural sector faces challenges due to climate change and the growing global population. Alkaline stress could adversely impact plant growth and crop production. This stressor diminishes water quality essential for crop cultivation, consequently impairing plant growth and overall productivity. Gamma-aminobutyric acid (GABA), a non-protein amino acid, may exhibit multifaceted roles in plant responses to adverse environmental conditions. Optimization of crop production in controlled environmental agriculture under artificial light attracted much attention. In the present study, we investigated the effects of different light spectra and GABA concentrations on Lollo Rosso lettuce plants under alkaline stress. Seedlings were placed under different light spectra [red (R), blue (B), white (W), 3R:1B, and 2R:1B:1far red (FR)] and treated with GABA (0 and 50 µmol). Alkaline conditions were instituted by applying NaHCO3 at a concentration of 40 mM. The experiment incorporated a control treatment without NaHCO3. In general, R light exposure caused the highest growth performance of lettuce plants. GABA augmented biomass production in control and alkaline-treated plants across all light spectra. Additionally, it increased the concentrations of photosynthetic and protective pigments under alkaline conditions. GABA also improved the photosynthetic performance under all light spectra. Non-photochemical quenching and pigmentation were enhanced by exposure to B light, especially in plants treated with GABA. Alkaline stress induced an increase in soluble carbohydrate content in the lettuce leaves. These findings highlight the support of GABA application in facilitating coping plants to alkaline stress

Light Intensity: The Role Player in Cucumber Response to Cold Stress

Low temperatures are a substantial limitation in the geographic distribution of warm-season crops such as cucumber (Cucumis sativus L.). Tolerance to low temperatures varies among different plant species and genotypes when changes in environmental cues occur. Therefore, biochemical and biophysical events should be coordinated to form a physiological response and cope with low temperatures. We examined how light intensity influences the effects of low temperature on photosynthesis and some biochemical traits. We used chlorophyll fluorescence imaging and polyphasic fluorescence transient to analyze cold stress damage by 4 &deg;C. Photosynthetic Photon Flux Densities (PPFDs) of 0, 300, and 600 &mu;mol m&minus;2 s&minus;1, in four accessions of cucumber, were investigated. The results show that the negative effects of cold stress are PPFD-dependent. The adverse effect of cold stress on the electron transport chain is more pronounced in plants exposed to 600 &mu;mol m&minus;2 s&minus;1 than the control and dark-exposed plants, indicated by a disturbance in the electron transport chain and higher energy dissipation. Moreover, biochemical traits, including the H2O2 content, ascorbate peroxidase activity, electrolyte leakage, and water-soluble carbohydrate, increased under low temperature by increasing the PPFD. In contrast, chlorophyll and carotenoid contents decreased under low temperature through PPFD elevation. Low temperature induced a H2O2 accumulation via suppressing ascorbate peroxidase activity in a PPFD-dependent manner. In conclusion, high PPFDs exacerbate the adverse effects of low temperature on the cucumber seedlings