Stomatal Conductance Research Articles

The Physiological Response of Salix matsudana for Water Pollution by 2,4-Dinitrophenol.

In this study, the effects of different concentrations of 2,4-dinitrophenol (2,4-DNP) stress on physiological parameters, as well as the uptake and removal of 2,4-DNP in Salix matsudana, were investigated using hydroponic simulation experiments to explore the potential of the use of Salix matsudana in the phytoremediation of wastewater polluted by 2,4-DNP. The results showed that PN (net photosynthetic rate), Tr (transpiration rate), Gs (stomatal conductance), Ls (stomatal limitation value), Fv/Fm (maximal quantum yield of PSII photochemistry), and qp (photochemical quenching coefficient) of Salix matsudana seedlings showed an overall decreasing trend, while Ci (intercellular CO2 concentration) showed an increasing trend with the increase in 2,4-DNP concentration. The net photosynthetic rate and intercellular carbon dioxide concentration showed an opposite trend in the leaves with the increase in 2,4-DNP stress concentration, and the inhibition of net photosynthesis by 2,4-DNP on Salix matsudana seedlings was mainly based on non-stomatal factors. In the 15 d incubation experiment, the values of SOD (superoxide dismutase), POD (peroxidase), and CAT (catalase) indexes were higher at low concentrations of 2,4-DNP stress, and all three enzymes reached their maximum values at 10 mg L-1 of 2,4-DNP and then decreased. Salix matsudana seedlings could tolerate 2,4-DNP stress well, which did not exceed 20 mg L-1. The toxicity of 2,4-DNP solution was significantly reduced after purification by Salix matsudana seedlings. The removal rate of 2,4-DNP was higher than 80% in each treatment group by Salix matsudana purified after 15 days. When the concentration of 2,4-DNP reached 20 mg L-1, the contents of MDA (malonicdialdehyde) were 55.62 mmol g-1, and the values of REC (relative conductivity) and LD (leaf damage) were 63.51% and 59.93%, respectively. The structure and function of the cell membrane in leaves were seriously damaged. With the increase in 2,4-DNP concentration, the removal of 2,4-DNP by Salix matsudana seedlings showed a decreasing trend. When the 2,4-DNP concentration was 5 mg L-1, the highest removal rate of 2,4-DNP by Salix matsudana seedlings was 95.98%, while when the 2,4-DNP concentration was 20 mg L-1, the highest removal rate was 86.76%. It is noted that the suitable, recommended concentration for the phytoremediation of 2,4-DNP contamination by Salix matsudana seedlings is between 8.81 and 13.78 mg L-1.

Elevated CO2 Concentration Enhances Drought Tolerance by Mitigating Oxidative Stress and Enhancing Carbon Assimilation in Foxtail Millet (Setaria italica)

ABSTRACTElevated CO2 concentration (eCO2) can modulate the response of crop plants to drought stress (DS). This study aimed to investigate the response of leaf gas exchange, chlorophyll fluorescence, antioxidant activities, osmotic adjustment substance, phytohormone and signal transduction regulatory enzymes, as well as related genes in foxtail millet to DS (water stress for 10 days), ambient condition (aCO2, 400 μmol mol−1) and eCO2 (600 μmol mol−1). eCO2 significantly increased the net photosynthetic rate, maximum net photosynthetic rate, chlorophyll a content, transpiration rate and stomatal conductance, but did not affect leaf instantaneous water‐use efficiency under DS. eCO2 also significantly enhanced the quantum yield of Photosystem II (PSII), photosynthetic electron transport, and proportion of open PSII reaction centers under DS. Moreover, eCO2 significantly increased abscisic acid (ABA) content, proline content, and the activities of peroxidase, superoxide dismutase, and calcium‐dependent protein kinase under DS, leading to a significant reduction in malondialdehyde content. eCO2 significantly increased the expressions of gene encoding ABA‐, stress‐ and ripening‐induced proteins and ABA‐responsive element binding factor under DS. Our results clearly demonstrated the vital role of eCO2 in mitigating the drought‐induced damage over ambient CO2 grown foxtail millet.

A Spatial Analysis of Coffee Plant Temperature and Its Relationship with Water Potential and Stomatal Conductance Using a Thermal Camera Embedded in a Remotely Piloted Aircraft

Coffee is a key agricultural product in national and international markets. Physiological parameters, such as plant growth indicators, can signal interruptions in these processes. This study aimed to characterize the temperature obtained by a thermal camera embedded in a remotely piloted aircraft (RPA) and evaluate its relationship with the water potential (WP) and stomatal conductance (gs) of an experimental coffee plantation using geostatistical techniques. The experiment was conducted at the Federal University of Lavras, Minas Gerais, Brazil. A rotary-wing RPA with an embedded thermal camera flew autonomously at a height of 10 m and speed of 10 m/s. Images were collected on 26 November 2019 (rainy season), and 11 August 2020 (dry season), between 9:30 am and 11:30 am. Data on gs and WP were collected in the field. The thermal images were processed using FLIR Tools 5.13, and temperature analysis and spatialization were undertaken using geostatistical tools and isocolor maps by Kriging interpolation in R 4.3.2 software. Field data were superimposed on final crop temperature maps using QuantumGIS version 3.10 software. The study found that with decreasing WP, stomatal closure and reduction in gs occurred, increasing the temperature due to water deficit. The temperature distribution maps identified areas of climatic variations indicating water deficit.

Engineering quantitative stomatal trait variation and local adaptation potential by cis-regulatory editing.

Cis-regulatory element editing can generate quantitative trait variation that mitigates extreme phenotypes and harmful pleiotropy associated with coding sequence mutations. Here, we applied a multiplexed CRISPR/Cas9 approach, informed by bioinformatic datasets, to generate genotypic variation in the promoter of OsSTOMAGEN, a positive regulator of rice stomatal density. Engineered genotypic variation corresponded to broad and continuous variation in stomatal density, ranging from 70% to 120% of wild-type stomatal density. This panel of stomatal variants was leveraged in physiological assays to establish discrete relationships between stomatal morphological variation and stomatal conductance, carbon assimilation and intrinsic water use efficiency in steady-state and fluctuating light conditions. Additionally, promoter alleles were subjected to vegetative drought regimes to assay the effects of the edited alleles on developmental response to drought. Notably, the capacity for drought-responsive stomatal density reprogramming in stomagen and two cis-regulatory edited alleles was reduced. Collectively our data demonstrate that cis-regulatory element editing can generate near-isogenic trait variation that can be leveraged for establishing relationships between anatomy and physiology, providing a basis for optimizing traits across diverse environments.

Agronomic Evaluation and Yield Potentials of Grafting of Piper nigrum and Piper colobrinum

Foot rot disease (Phytophthora capsica) is Indonesia's primary challenge in cultivating pepper (Piper nigrum). Grafting to another Piper species, Piper coclobrinum, or melada (the local name), is a potential solution to increase resistance to this disease. The use of melada as rootstock has shown promising results during the seedling phase, but it has not been thoroughly evaluated during the production phase. The study was conducted in the pepper grower’s location in Puput and Simpang Katis Villages, Central Bangka, Bangka Belitung Islands Province. The study used kapok (Ceiba petandra) as the standard; plant morphology, leaf area, leaf thickness, and crown diameter for grafted melada and non-grafted pepper were recorded. Harvest variables included panicle length, panicle weight, the number of fruits per panicle, and fruit diameter, measured in three different areas of the canopy: the lower area (0-1 meter above the ground surface), the middle area (1-2 meters above the ground surface), and the top area (more than 2 meters above the ground surface). Physiological variables measured included rates of photosynthesis, stomatal conductance, transpiration rate, intercellular CO2, and CO2 conductance. The study demonstrated that the grafted pepper plants had a larger leaf area than the non-grafted pepper plants; the panicle weight and the number of fruits per panicle were higher. Panicles located in the middle zone of the plant canopy tended to be longer for grafted and non-grafted peppers. Panicle weight, fruit size, and the number of fruits per panicle were generally more significant at the top of the plant canopy. In all parts of the canopy, grafted peppers exhibited larger fruit size, greater panicle weight, and a higher number of fruits per panicle than non-grafted “Nyelungkup” peppers, highlighting the potential of melada as a rootstock for pepper plants.

Phytohormones and Mineral Nutrient Changes in Young Plants of Grapevine Genotypes at Different Growth Stages

Climate change is considered a threat for viticulture by altering phenology, yield, and key physiological processes. The plant responses depend on the genotype characteristics and the microclimate of crop area. In this research, “Castellana Negra”, “Negramoll”, and “Tintilla” were cultivated for 102 days, and physiological variables were assessed under natural conditions. Results indicated similar trends in growth between “Negramoll” and “Tintilla”, while ”Castellana Negra” grew slowly and possessed fewer leaves compared to the other genotypes. Stomatal conductance was constant among the genotypes, excepting “Negramoll”, which demonstrated lower values at d 76 compared to “Castellana Negra” and “Tintilla”, coinciding with the elevated leaf temperature. Regarding the hormonal changes, “Castellana Negra” accumulated the highest concentration of salicylic acid (SA) compared to “Negramoll” and “Tintilla”, which showed similar content. Furthermore, an antagonistic change between SA and jasmonic acid (JA) was observed in all genotypes, as well as between abscisic acid (ABA) and JA at the beginning and end of the trial. The variations in micronutrients did not show a clear tendency between cultivars. Therefore, to thoroughly elucidate the role of phytohormones and other physiological factors in the growth and development of these genotypes under varying environmental conditions, long-term experiments could be conducted.

How the vertical gradient of light in the understorey and water seasonality affect leaf traits of Vanilla phaeantha (Orchidaceae), a crassulacean acid metabolism (CAM) hemiephyte.

Structural and physiological leaf traits and their plasticity were compared in the hemiepiphyte Vanilla phaeantha . This species grows along a phorophyte reaching different understorey positions and exhibiting diverse responses to environment changes. We analysed three height strata above the ground, establishing a light gradient, and considering seasonal water fluctuations. The upper leaves had higher area and mass and were less pigmented. The dry season induced a reduction of approximately 2h of stomatal opening over the diel 24h crassulacean acid metabolism (CAM) cycle in the leaves at all understorey positions. The leaves more exposed to sunlight were larger with higher titratable acidity during the rainy season, while the leaves near the ground maintained the same rates of stomatal conductance and nocturnal acidification between seasons, with lowest values of carbon isotopes in the rainy season. Our research showed that some structural leaf traits (such as specific leaf mass, biomass, and saturated water content) are sensitive to variation in understorey position. In contrast, other physiological traits (stomatal conductance, transpiration, and fluorescence parameters) are more sensitive to seasonal variations. The results are a novelty in assessing the variation of CAM along the same plant in a height gradient and under field conditions.

Insight into physiological and biochemical markers against formaldehyde stress in spider plant (Chlorophytum comosum L.).

Formaldehyde is a prominent volatile organic compound and also considered as an indoor air pollutant. Chlorophytum comosum, an indoor plant, has been reported to metabolize indoor formaldehyde. But the phytotoxic effects of formaldehyde, being a pollutant, on C. comosum are not well explored. Furthermore, C. comosum responses that can be considered as markers at the physiological and biochemical level against formaldehyde stress are not yet investigated. Therefore, the current research study was aimed to evaluate such potential markers against formaldehyde in C. comosum. Briefly, C. comosum was exposed to 5-, 10-, and 20-ppm formaldehyde doses in an airtight glass chamber. Plant samples were then taken to analyze morpho-anatomical, physiological, and biochemical responses after short (2, 4, and 6h), medium (12 and 24h), and extended durations (48 and 96h) for each tested dose. Application of 10 and 20ppm formaldehyde doses leads to a significant incline in enzymatic antioxidants. Formaldehyde concentration of 10ppm leads to a maximum increase in catalase (30.30 U/mg of protein), guaiacol peroxidase (135.64 U/mg of protein), and superoxide dismutase (44.76 U/mg of protein) compared to their respective controls. A significant change is also observed in non-enzymatic parameters, including total phenolic content, which ranged from 3.62mg GAE/g (control) to 10.51mg GAE/g, total antioxidants vary from 27.37% (control) to 85.05% in 20ppm formaldehyde, respectively. However, formaldehyde application negatively affected the physiological responses of C. comosum by reducing its photosynthetic rate, transpiration rate, and stomatal conductance. Additionally, extended exposure of C. comosum to 10- and 20-ppm formaldehyde doses leads to visible leaf damage. Principal component analysis indicated that enzymatic parameters including SOD, CAT, and GPX and non-enzymatic parameters including MDA, TPC, TFC, TAOs, carotenoids, TSS, and intercellular CO2 contributed the most to the total variance. Thus, these parameters have potential to serve as physiological and biochemical markers in C. comosum against formaldehyde stress.

Organic matter-induced physiological responses and modulation of the enzymatic system in Sorghum bicolor (L) Moench genotypes cultivated in saline soil

Sorghum bicolor (L.) Moench is a crop with numerous applications that serves as a food source for humans and animals. However, soils with high salt concentrations compromise the initial development of the crop, and the addition of organic matter can mitigate the damage caused by salinity. The present study aimed to verify the effect of organic matter on salinity on the physiology and enzymatic profiles of two sorghum varieties, BRS Ponta Negra and BRS 373. The experiment was conducted in a completely randomized design (DIC) in a 4 x 4 x 2 arrangement, using different doses of organic matter as recommended (100%, 200%, 300%, and 400%) and the two sorghum varieties, with 4 replications. The variables analysed were: photosynthetic rate (A), transpiration (E), stomatal conductance (Gs), and enzymatic activity of ascorbate peroxidase (APX), polyphenoloxidase (POL), and catalase (CAT). The results showed that the A, E, and Gs responded differently to different doses of organic matter (OM); these responses were influenced by the isolated effects of the varieties or doses of organic matter, and their behaviour differed between the two analysed varieties. The A, E, and Gs showed contrasting response patterns between different doses of OM in variety 1 (BRS Ponta Negra) and variety 2 (BRS 373). These responses were influenced by the isolated effects of the varieties and/or doses of organic matter, showing different behaviours among the tested varieties.

Optimizing micropropagation of Miscanthus sinensis ‘Gold Bar’ by shortening the production cycle and reducing acclimation stress through the use of selected growth regulators

Miscanthus, with its decorative qualities and low cultivation requirements in terms of soil fertility and temperature, is the most popular grass in gardens and urban areas. For years, micropropagation has been regarded as an effective method of its production. However, in order to meet the demands of customers and provide adequate quantities of high-quality planting materials, it is necessary to develop more efficient methods of Miscanthus production. The present study evaluated the influence of different media on Miscanthus sinensis (Thunb.) Andersson (silver grass) multiplication as well as assessing the effect of different concentrations of selected cytokinins and auxins on multiplication and rhizogenesis. To shorten the production cycle and reduce costs, ex vitro rooting was combined with acclimatization, and selected growth regulators were used to decrease stress associated with external conditions. Biochemical analyses were conducted at each stage to determine the content of basic organic compounds, hydrogen peroxide (H2O2) and catalase activity. Stomatal function was assessed at the acclimatization stage. The obtained results allowed for the production cycle of plants propagated in tissue culture to be shortened by simultaneous rooting and acclimatization of microcuttings sprayed with abscisic acid (ABA). This regulator has been shown to effectively reduce plant stress associated with acclimatization by reducing H2O2 concentration and increasing assimilation pigment content. Growth regulators reduced the number of stomata that developed on the leaves of silver grass and led to lower stomatal conductance. H2O2 should be considered not only a stress marker but a vital signaling molecule.

Effects of mineral fertilization (NPK) on combined high temperature and ozone damage in rice

BackgroundIncreasing concern has recently been highlighted regarding crop damage due to extreme weather events caused by global warming and the increased production of ground-level ozone. Several studies have investigated rice growth in response to fertilization conditions under various environmental stress conditions; however, studies on growth development in response to fertilization conditions under combined high-temperature/ozone treatment conditions are scarce. In this study, we aimed investigate the growth and physiological development of rice under combined high temperature and ozone treatment conditions and to reveal the damage-mitigation effects of NPK fertilization treatments.ResultsThe plants were treated with varying levels of NPK [N2 (N-P-K: 9.0-4.5-4.0 kg/a), P2 (4.5-9.0-4.0 kg/a), K2 (4.5-4.5-8.0 kg/a), and control (4.5-4.5-4.0 kg/10a).] under combined high-temperature (35 ℃) and ozone (150 pb) treatment conditions. Analysis of the growth metrics, including plant height, leaf age, dry weight, and the plant height/leaf age (PH/L) ratio were revealed that combined high-temperature/ozone treatment promoted the phenological development indicated by increasing leaf age but decreased the plant height and dry weight indicating its negative effect on quantitative growth. The effects of this combined high-temperature/ozone treatment on growth were alleviated by NPK fertilization, particularly in K2 treatment but worsened in N2 treatment. Visible damage symptoms in rice leaves induced by exposure to the combined stressors was also alleviated by the K2 treatment. At the physiological level, K2 treatment reduced the expression of OsF3H2, which is associated with antioxidant activity, suggesting that potassium improved stress tolerance. Additionally, expression of genes related to abscisic acid (ABA) metabolism showed increased OsNECD (ABA synthesis) and decreased OsCYP707A3 (ABA degradation) in the K2 treatment, promoting a stronger adaptive stress response. Stomatal conductance measurements indicated a slight increase under K2 treatment, reflecting enhanced regulation of stomatal function during stress.ConclusionThe study highlights the potential of potassium fertilization to mitigate combined high-temperature and ozone stress in rice, suggesting it as a strategy to improve crop resilience and optimize fertilization. The findings offer insights into fertilization treatments and can guide future research on stress tolerance in crops.

Identification of High-Photosynthetic-Efficiency Wheat Varieties Based on Multi-Source Remote Sensing from UAVs

Breeding high-photosynthetic-efficiency wheat varieties is a crucial link in safeguarding national food security. Traditional identification methods necessitate laborious on-site observation and measurement, consuming time and effort. Leveraging unmanned aerial vehicle (UAV) remote sensing technology to forecast photosynthetic indices opens up the potential for swiftly discerning high-photosynthetic-efficiency wheat varieties. The objective of this research is to develop a multi-stage predictive model encompassing nine photosynthetic indicators at the field scale for wheat breeding. These indices include soil and plant analyzer development (SPAD), leaf area index (LAI), net photosynthetic rate (Pn), transpiration rate (Tr), intercellular CO2 concentration (Ci), stomatal conductance (Gsw), photochemical quantum efficiency (PhiPS2), PSII reaction center excitation energy capture efficiency (Fv’/Fm’), and photochemical quenching coefficient (qP). The ultimate goal is to differentiate high-photosynthetic-efficiency wheat varieties through model-based predictions. This research gathered red, green, and blue spectrum (RGB) and multispectral (MS) images of eleven wheat varieties at the stages of jointing, heading, flowering, and filling. Vegetation indices (VIs) and texture features (TFs) were extracted as input variables. Three machine learning regression models (Support Vector Machine Regression (SVR), Random Forest (RF), and BP Neural Network (BPNN)) were employed to construct predictive models for nine photosynthetic indices across multiple growth stages. Furthermore, the research conducted principal component analysis (PCA) and membership function analysis on the predicted values of the optimal models for each indicator, established a comprehensive evaluation index for high photosynthetic efficiency, and employed cluster analysis to screen the test materials. The cluster analysis categorized the eleven varieties into three groups, with SH06144 and Yannong 188 demonstrating higher photosynthetic efficiency. The moderately efficient group comprises Liangxing 19, SH05604, SH06085, Chaomai 777, SH05292, Jimai 22, and Guigu 820, totaling seven varieties. Xinmai 916 and Jinong 114 fall into the category of lower photosynthetic efficiency, aligning closely with the results of the clustering analysis based on actual measurements. The findings suggest that employing UAV-based multi-source remote sensing technology to identify wheat varieties with high photosynthetic efficiency is feasible. The study results provide a theoretical basis for winter wheat phenotypic monitoring at the breeding field scale using UAV-based multi-source remote sensing, offering valuable insights for the advancement of smart breeding practices for high-photosynthetic-efficiency wheat varieties.

Impact of Elevated Atmospheric and Intercellular CO2 on Plant Defense Mechanisms

AbstractThis review explores the complex relationship between carbon dioxide (CO2) levels and secondary metabolites in leaves, emphasizing their role in plant defense mechanisms. The synthesis of different research that has been done ranges from the influence of CO2 on photosynthesis, metabolic pathways, and the synthesis of secondary metabolites, crucial in protecting plants against environmental stressors, especially pathogens. The paper highlights the significance of various factors such as light intensity, water supply, and temperature in regulating stomatal conductance and subsequent CO2 assimilation. Additionally, it discusses the diverse secondary metabolites found in plants, including phenolic compounds, terpenoids, and tannins, and their antioxidant properties. The review suggests that elevated CO2 levels may enhance plant defense responses by influencing the production of secondary metabolites. The paper also explores the complex interplay between CO2 levels, metabolic activity, and defense mechanisms, providing valuable insights into how plants dynamically adjust their metabolism to cope with environmental challenges, highlighting the interaction of adaptation and physiology in plants, offering a holistic understanding of the biochemical and physiological processes involved in plant defense.

Wind speed affects the rate and kinetics of stomatal conductance.

Understanding the relationship between wind speed and gas exchange in plants is a longstanding challenge. Our aim was to investigate the impact of wind speed on maximum rates of gas exchange and the kinetics of stomatal responses. We conducted experiments in different angiosperm and fern species using an infrared gas analyzer equipped with a controlled leaf fan, enabling precise control of the boundary layer conductance. We first showed that the chamber was adequately mixed even at extremely low wind speed (<0.005 m s-1) and evaluated the link between fan speed, wind speed, and boundary layer conductance. We observed that higher wind speeds led to increased gas exchange of both water vapor and CO₂, primarily due to the increase in boundary layer conductance. This increase in transpiration subsequently reduced epidermal pressure, leading to stomatal opening. We documented that stomatal opening in response to light was 2.5 times faster at a wind speed of 2 m s-1 compared to minimal wind speed in Vicia faba, while epidermal peels in a buffer with no transpiration exhibited a similar opening rate. The increase in stomatal conductance under high wind was also observed in four angiosperm species under field conditions, but it was not observed in Boston fern (Nephrolepis exaltata), which lacks epidermal mechanical advantage. Our findings highlight the significant impact of boundary layer conductance on determining gas exchange rates and the kinetics of gas exchange responses to environmental changes.

Assessment of Meteorological Drought in a Changing Environment: An Example in the Upper Yangtze River

AbstractRecent studies have suggested that drought projections using Palmer drought severity index (PDSI) and standardized evapotranspiration precipitation index (SPEI) may overestimate drought severity. This overestimation occurs because the potential evapotranspiration (PET) calculations fail to consider the interactive effects of vegetation responses such as increased leaf area index (LAI) and constrained stomatal conductance, which are influenced by elevated atmospheric CO2 concentrations ([CO2]). To address this issue, our study replaced the traditional Penman‐Monteith (PM) equation with a recently proposed PET equation that includes the effects of changing [CO2] and LAI to assess droughts at monthly scale in the Upper Yangtze River basin, which experiences the vegetation greening. The findings indicated a consistent increasing trend in drought conditions with minimal discrepancy between the two equations over the historical period (1986–2017). This consistency arises because the water‐saving effects of increased [CO2] and the greening effects of rising LAI largely counterbalance each other. However, for the future period (2018–2100), projections using PM equation predicted an intensification of drought conditions. In contrast, the improved SPEI indicated no significant drought variations, and the improved PDSI suggested a wetting trend. This divergence can be attributed to the water‐saving effects increasingly outweighing the greening effects, as PET shows a decreasing sensitivity to LAI with LAI increasing, but maintains a near‐constant sensitivity to elevated [CO2]. Consequently, the indices based on PM equation tend to overestimate future drought severity. Overall, this study demonstrates that the new PET estimation method is more capable of responding to the changing environment.

Morphophysiological adaptations and fragrance profile analysis of two relocated orchid species

This study investigates the morpho-physiological adaptations and fragrance profiles of 2 relocated orchid species, Cattleya aclandiae x Brassavola Little star (V1) and Dendrobium var. Meesangnil (V2), following their translocation from Nagercoil to Coimbatore, India. The research aims to elucidate the mechanisms underlying successful acclimatization of these fragrant orchids to a new environment, with implications for horticulture, conservation and therapeutic applications. Comprehensive analyses were conducted on vegetative growth parameters, flowering characteristics, physiological responses and volatile organic compound (VOC) profiles. Morphological assessments revealed distinct adaptive strategies between the 2 species, with Dendrobium exhibiting superior vertical growth (39.13 cm) and leaf production (9 leaves/plant), while Cattleya developed larger leaves (30.483 cm length, 7.178 cm breadth) and longer internodes (5.061 cm). Flowering characteristics also differed significantly, with Cattleya demonstrating earlier spike emergence and floret opening. Physiological analyses using a CI-340 Handheld Photosynthesis System showed higher photosynthetic rates, transpiration rates and stomatal conductance in Dendrobium, suggesting a more resource-acquisitive strategy. Gas chromatography-mass spectrometry (GC-MS) analysis identified unique VOC profiles for each species, with 30 compounds detected in both varieties, including notable compounds such as n-Hexadecanoic acid, Octadecanoic acid and beta-Sitosterol. The study also explored potential applications in therapeutic horticulture, highlighting the diverse sensory and educational value of these orchid species. This comprehensive analysis of morphological, physiological and biochemical adaptations provides valuable insights into orchid acclimation processes and their potential for conservation and horticultural applications, contributing to our understanding of plant adaptability in the face of environmental changes and offering a foundation for future studies on orchid biology, ecology and therapeutic uses.

Photosynthetic Traits of Quercus coccifera Green Fruits: A Comparison with Corresponding Leaves during Mediterranean Summer

Fruit photosynthesis occurs in an internal microenvironment seldom encountered by a leaf (hypoxic and extremely CO2-enriched) due to its metabolic and anatomical features. In this study, the anatomical and photosynthetic traits of fully exposed green fruits of Quercus coccifera L. were assessed during the period of fruit production (summer) and compared to their leaf counterparts. Our results indicate that leaf photosynthesis, transpiration and stomatal conductance drastically reduced during the summer drought, while they recovered significantly after the autumnal rainfalls. In acorns, gas exchange with the surrounding atmosphere is hindered by the complete absence of stomata; hence, credible CO2 uptake measurements could not be applied in the field. The linear electron transport rates (ETRs) in ambient air were similar in intact leaves and pericarps (i.e., when the physiological internal atmosphere of each tissue is maintained), while the leaf NPQ was significantly higher, indicating enhanced needs for harmless energy dissipation. The ETR measurements performed on leaf and pericarp discs at different CO2/O2 partial pressures in the supplied air mixture revealed that pericarps displayed significantly lower values at ambient gas levels, yet they increased by ~45% under high CO2/O2 ratios (i.e., at gas concentrations simulating the fruit’s interior). Concomitantly, NPQ declined gradually in both tissues as the CO2/O2 ratio increased, yet the decrease was more pronounced in pericarps. Furthermore, net CO2 assimilation rates for both leaf and pericarp segments were low in ambient air and increased almost equally at high CO2, while pericarps exhibited significantly higher respiration. It is suggested that during summer, when leaves suffer from photoinhibition, acorns could contribute to the overall carbon balance, through the re-assimilation of respiratory CO2, thereby reducing the reproductive cost.

Water Loss From Bagged Leaves During Storage: Why and When?

In ecophysiology leaves are frequently stored for hours after sampling before measuring their leaf water potential (Ψleaf). Here, we address a previously unidentified source of error, that metabolic heat generation can cause continuous water loss from leaves stored in impermeable bags, leading to a Ψleaf drop over time. We tested Ψleaf drop rates under various conditions: two bag materials, two species, initial Ψleaf above or below the turgor loss point (Ψtlp), and storage at 25°C versus 4°C. We partitioned leaf water loss due to condensation on the inner bag surface or permeation through the bag. We found that Ψleaf dropped by up to 0.39 MPa per hour, with 41%-89% of the water leaving the leaf condensed on the inner bag surface. Plastic bags showed higher Ψleaf drop rates than aluminium bags, and leaves above Ψtlp experienced greater drops. Storing leaves at 4°C reduced the Ψleaf drop rate by 60% compared to 25°C. Leaves were 0.2-0.3°C warmer than the bags, likely due to metabolic heating. Our energy balance model suggests that water loss is lower when storing leaves at cooler temperatures, using leaves with low stomatal conductance, deflated bags, and leaves with low Ψleaf.

Research on the Mechanism of Growth of Codonopsis pilosula (Franch.) Nannf. Root Responding to Phenolic Stress Induced by Benzoic Acid.

Soil autotoxic chemosensory substances have emerged as the predominant environmental factors constraining the growth, quality, and yield of Codonopsis pilosula in recent years. Among a vast array of chemosensory substances, benzoic acid constitutes the principal chemosensory substance in the successive cultivation of C. pilosula. However, the exploration regarding the stress exerted by benzoic acid on the growth and development of C. pilosula remains indistinct, and there is a scarcity of research on the mechanism of lobetyolin synthesis in C. pilosula. In the current research, it was discovered that exposure to benzoic acid at a concentration of 200 mmol/L conspicuously attenuated the plant height, root length, total length, fresh weight, root weight, root thickness, chlorophyll content, electrolyte osmolality, leaf intercellular CO2 concentration (Ci), net photosynthesis rate (Pn), transpiration rate (Tr), and leaf stomatal conductance (Gs) of C. pilosula. Benzoic acid (200 mmol/L) significantly enhanced the activity of root enzymes, including superoxide dismutase (SOD), malondialdehyde (MDA), and peroxidase (POD), as well as the accumulation of polysaccharides and lobetyolins (polyacetylene glycosides) in the roots of C. pilosula. In this study, 58,563 genes were assembled, and 7946 differentially expressed genes were discovered, including 4068 upregulated genes and 3878 downregulated genes. The outcomes of the histological examination demonstrated that benzoic acid stress augmented the upregulation of genes encoding key enzymes implicated in the citric acid cycle, fatty acid metabolism, as well as starch and sucrose metabolic pathways. The results of this investigation indicated that a moderate amount of benzoic acid could enhance the content of lobetyolin in C. pilosula and upregulate the expression of key coding genes within the signaling cascade to improve the resilience of C. pilosula lobetyolin against benzoic acid stress; this furnished a novel perspective for the study of C. pilosula lobetyolin as a potential substance for alleviating benzoic acid-induced stress.

Growth, Evapotranspiration, Gas Exchange and Chl a Fluorescence of Ipê-Rosa Seedlings at Different Levels of Water Replacement.

In general, young plants in the establishment phase demonstrate sensitivity to changes in environmental conditions, especially regarding water availability. The effects of the seasonality of biophysical processes on plant physiology can trigger differential responses, even within the same region, making it necessary to conduct studies that characterize the physiological performance of the species at different spatial and temporal scales, making it possible to understand their needs and growth limits under water stress conditions. This paper aimed to evaluate the growth, gas exchange and Chl a fluorescence in ipê-rosa seedlings subjected to levels of water replacement (LWRs) of 100, 75, 50 and 25% in a greenhouse. The morphometric variables of plant height, diameter at stem height, numbers of leaves and leaflets, root length and volume, plant dry mass and leaf area were evaluated. The potential evapotranspiration of seedlings (ETc) was obtained using direct weighing, considering the water replacement of 100% of the mass variation between subsequent days as a reference; the cultivation coefficients (kc) were obtained using the ratio between ETc and the reference evapotranspiration (ETo) obtained by the Penman-Monteith FAO-56 method. Biomass and evapotranspiration data were combined to determine water sensitivity. Diurnal fluxes of gas exchange (net photosynthesis rate, transpiration rate, stomatal conductance, internal and atmospheric carbon ratio, water use efficiency and leaf temperature) and Chl a fluorescence (Fv/Fm, ΦPSII, ETR, Fv'/Fm', NPQ and qL) were evaluated. Water restriction caused reductions of 90.9 and 84.7% in the increase in height and diameter of seedlings subjected to 25% water replacement when compared to seedlings with 100% water replacement. In comparison, biomass accumulation was reduced by 96.9%. The kc values increased throughout the seedling production cycle, ranging from 0.59 to 2.86. Maximum water sensitivity occurred at 50% water replacement, with Ky = 1.62. Maximum carbon assimilation rates occurred in the morning, ranging from 6.11 to 12.50 µmol m-2 s-1. Ipê-rosa seedlings regulate the physiology of growth, gas exchange and Chl a fluorescence depending on the amount of water available, and only 25% of the water replacement in the substrate allows the seedlings to survive.