Water Gas Exchange Research Articles

The impact of heterogeneity of the air-blood barrier on control of lung extravascular water and alveolar gas exchange.

The architecture of the air-blood barrier is effective in optimizing the gas exchange as long as it retains its specific feature of extreme thinness reflecting, in turn, a strict control on the extravascular water to be kept at minimum. Edemagenic conditions may perturb this equilibrium by increasing microvascular filtration; this characteristically occurs when cardiac output increases to balance the oxygen uptake with the oxygen requirement such as in exercise and hypoxia (either due to low ambient pressure or reflecting a pathological condition). In general, the lung is well equipped to counteract an increase in microvascular filtration rate. The loss of control on fluid balance is the consequence of disruption of the integrity of the macromolecular structure of lung tissue. This review, merging data from experimental approaches and evidence in humans, will explore how the heterogeneity in morphology, mechanical features and perfusion of the terminal respiratory units might impact on lung fluid balance and its control. Evidence is also provided that heterogeneities may be inborn and they could actually get worse as a consequence of a developing pathological process. Further, data are presented how in humans inter-individual heterogeneities in morphology of the terminal respiratory hinder the control of fluid balance and, in turn, hamper the efficiency of the oxygen diffusion-transport function.

Drought susceptibility of southern African C4 grasses: Phylogenetically and photosynthetically determined?

Abstract Factors that determine C4 grass distributions have been well documented, with evidence in the literature for C4 photosynthetic subtypes displaying varying levels of drought susceptibility. However, the interactions between C4 photosynthetic subtype and phylogeny add complexity and are relatively under studied. We use species distribution modelling to determine the influence of rainfall on distribution patterns of representative C4 grass families and subtypes. Select C4 grass species, representing different photosynthetic subtypes (NADP‐Me and NAD‐Me) and lineages (Panicoideae and Aristidoideae), were subjected to a progressive 58‐day drought period and recovery phase, to explore drought responses through leaf water relations, gas exchange and chlorophyll fluorescence. We show Panicoideae NADP‐Me species to be more susceptible to drought than both Panicoideae NAD‐Me and Aristidoideae NADP‐Me species due to apparent greater metabolic impairment. The differences between groups were related to how rapidly photosynthesis declines with exposure to drought and the rate of recovery postdrought, rather than the maximum extent of photosynthetic decline. The mechanisms for the relative maintenance of plant water status differed between the Panicoideae NAD‐Me species, which utilized greater stomatal control, and the Aristidoideae NADP‐Me species, which maintained water uptake through osmotic adjustment. Synthesis. We show here that drought susceptibility differs both phylogenetically and according to photosynthetic subtype, but that the role of phylogeny may outweigh physiological control. This research adds novel insight into the physiological differences behind observed rainfall‐related differences in C4 grass distribution patterns. Read the free Plain Language Summary for this article on the Journal blog.

Salt Stress-Regulation of Root Water Uptake in a Whole-Plant and Diurnal Context.

This review focuses on the regulation of root water uptake in plants which are exposed to salt stress. Root water uptake is not considered in isolation but is viewed in the context of other potential tolerance mechanisms of plants-tolerance mechanisms which relate to water relations and gas exchange. Plants spend between one third and half of their lives in the dark, and salt stress does not stop with sunset, nor does it start with sunrise. Surprisingly, how plants deal with salt stress during the dark has received hardly any attention, yet any growth response to salt stress over days, weeks, months and years is the integrative result of how plants perform during numerous, consecutive day/night cycles. As we will show, dealing with salt stress during the night is a prerequisite to coping with salt stress during the day. We hope to highlight with this review not so much what we know, but what we do not know; and this relates often to some rather basic questions.

Forest Health Assessment in Four Jordanian Reserves Located in Semi-Arid Environments

Healthy forests are essential to human life because they provide food, energy, and other benefits including carbon sequestration. The objective of this study was to assess the forests health status in Mediterranean ecosystems, specifically, arid to semi-arid. Four forest reserves directed by Royal Society for the Conservation of Nature, Jordan were evaluated. Plant health indicators [(gas exchange (photosynthesis, stomatal conductance, transpiration), chlorophyll, middy stem water potential (Ψsmd), relative water content], regeneration, lichens, plant disease, as well as soil variables (respiration CO2-C, electrical conductivity (EC), pH, microorganisms’ abundance) were measured. The Ψsmd values in those semi-arid/arid ecosystems were within the normal ranges (−0.3 to −1.3 MPa) in spring but was under extreme water stress (−1.6 to −5.3 MPa) in summer in three reserves. Similarly, gas exchange variables reduced by 25%–90% in summer (compared to spring) across the studied forests. Although the regeneration (seedling per 1000 m2) was higher than 100 in two forest (Ajloun and Dibbeen), the number of seedlings in hiking sites was extremely low in both forests. Soil health indicators reveled that soil respiration CO2-C were higher than 25 mg kg−1 in two forests [Ajloun, Dibbeen, (except hiking zone)]. The mean soil saprophytes (number g−1) ranged from 86 to 377 across the forests reserves. In addition, the mean arbuscular mycorrhizal fungi (spores 100g−1 soil) was between 350 and 877. Soil EC was consistently optimal (less than 0.5 dS m−1) and pH was slightly basic (7.5–8.3) across the reserves. The results revealed that the fluctuation of rainfall and anthropogenic pressures (grazing, hiking) led to partial forest degradation. When forests (Dana Biosphere Reserve) received 81 mm annual precipitation, Ψsmd values in Juniperus phoenicea at summer ranged from −4.4 to −5.3 MPa, regeneration and lichens were less than 20 per 1000 m2, and several trees were dead after infected with soil and air borne pathogens including wilt diseases and die back. Intensive hiking activities (Dibbeen forests, tourism area) and heavy grazing (Yarmouk frosts) reduced regeneration, lichens and soil respiration. Interestingly, the native species had better water relations (RWC, Ψsmd) and gas exchange performance than the introduced species. Overall, it is better to grow native species, and exclude anthropogenic pressure on the territory of introduced species. The conservation programs must persist to sustain several native historical forest trees including Juniperus phoenicea (>600 year old), Quercus ithaburensis (>500 year old), and Pinus halepensis (>100 year old) at Mediterranean semi-arid forests.

Water Relation, Gas Exchange Characteristics and Yield Performance of Selected Mungbean Genotypes under Low Soil Moisture Condition

Among the environmental constraints, the growth and yield of crops are seriously impaired by moisture stress. With this view, an experiment was conducted to observe genotypic differences in water relation, gas exchange characteristics and yield performance of mungbean under low soil moisture conditions. Experimental variables consisted of five drought tolerant genotypes (G88, G108, G141,varietiesG186), one susceptible genotype (G43) and two standard check variety (BU mug 5, Binnamoog-8) which assigned to two moisture regimes viz., water regime A ((80 to 90% field capacity (FC)) and water regime B (40 to 50% FC). Results showed that water saturation deficit, water uptake capacity and transpiration rate were the lowest in tolerant genotypes G88 followed by genotypes G141, while those were the highest in susceptible genotype G43 under low soil moisture conditions. Contrarily, the highest amount of relative water content and water retention capacity were found in tolerant genotypes G141, G108 and G88 and the lowest was recorded in susceptible genotype G43 under low soil moisture conditions. In the case of the photosynthetic rate and stomatal conductance, the tolerant genotype G141, G88 and G108 showed the higher values at moisture stress condition. The highest total chlorophyll content and proline content were also found in tolerant genotype G88 followed by G141 and G108, and the lowest was found in susceptible genotype G43 under moisture stress conditions. Irrespective of genotypes, moisture stress significantly decreased the yield attributes and yield of mungbean genotypes. However, the highest seed yield per plant (12.11 g) was found in tolerant genotype G88 under low soil moisture conditions because of its lowest reduction rate of yield attributes under moisture stress. Similar responses were also observed in tolerant genotypes G141 and G108. Therefore, the genotypes G88, G108 and G141 showed better performance in the case of water relation and gas exchange characteristics which might be contribute to higher yield of those genotypes.

Influence of Silicon on Tolerance to Water Deficit of Peach Trees

Water deficit in young fruit trees can reduce growth and future orchard productivity. Exogenous silicon (Si) applications have been associated with induced resistance to biotic and abiotic stresses such as water deficit, but the role of Si in fruit trees is still largely unexplored. The aim of the study was to evaluate the effect of Si applications on water status and gas exchange of young peach trees. This study comprises two experiments arranged in a factorial design with two water regimens (well-irrigated or water-stressed) and three Si concentrations (0, 10, or 20 mg⋅L−1 in the first experiment; 0, 20, or 40 mg⋅L−1 in the second experiment). Si applications via foliar spray were performed weekly after the water regimens were clearly established. Tree water status (midday stem water potential), and gas exchange parameters (CO2 assimilation, leaf transpiration, stomatal conductance, leaf water use efficiency) were measured. Si application at 10 or 20 mg⋅L−1 improved water status of water-stressed trees without affecting gas exchange, but 40 mg⋅L−1 reduced CO2 assimilation. Thus, foliar applications of Si could be a promising strategy for nonirrigated, nonbearing orchards to maintain their water status during dry periods and/or improve their recovery from water deficit.

Pematahan Dormansi Benih Kopi Arabika Kerinci dengan Berbagai Bahan Perendaman

Coffee seeds take a long time to germinate, as the tough seed coat can cause dormancy. This is because water absorption and gas exchange are disturbed and the seed coat is a mechanical barrier. Breaking of dormancy to maximize germination needs to be done before sowing the seeds. The aim of this study was to obtain an appropriate and effective soaking agent for breaking the dormancy of Kerinci arabica coffee seeds. The research was conducted using a Randomized Block Design (RBD), with various treatments for coffee seed immersion, namely: without immersion (p0), immersion with coconut water (p1), immersion in hot water (p2), and immersion with alang-alang root extract (p3). Parameters observed in the study were: maximum growth potential, germination and abnormal sprouts. The results of this study were (1) Proper and effective soaking materials were obtained for breaking the dormancy of Kerinci arabica coffee seeds, (2) Soaking Kerinci arabica coffee seeds with coconut water was more effective for maximum growth potential, germination and abnormal germination.

Impacts of Green Fraction Changes on Surface Temperature and Carbon Emissions: Comparison under Forestation and Urbanization Reshaping Scenarios

Global land cover dynamics alter energy, water, and greenhouse gas exchange between land and atmosphere, affecting local to global weather and climate change. Although reforestation can provide localized cooling, ongoing land use land cover (LULC) shifts are expected to exacerbate urban heat island impacts. In this study, we monitored spatiotemporal changes in green cover in response to land use transformation associated with the Khyber Pakhtunkhwa (KPK) provincial government’s Billion Tree Tsunami Project (BTTP) and the Ravi Urban Development Plan (RUDP) initiated by the provincial government of Punjab, both in Pakistan. The land change modeler (LCM) was used to assess the land cover changes and transformations between 2000 and 2020 across Punjab and KPK. Furthermore, a curve fit linear regression model (CFLRM) and sensitivity analysis were employed to analyze the impacts of land cover dynamics on land surface temperature (LST) and carbon emissions (CE). Results indicated a significant increase in green fraction of +5.35% under the BTTP, achieved by utilizing the bare land with an effective transition of 4375.87 km2. However, across the Punjab province, an alarming reduction in green fraction cover by −1.77% and increase in artificial surfaces by +1.26% was noted. A significant decrease in mean monthly LST by −4.3 °C was noted in response to the BTTP policy, while an increase of 5.3 °C was observed associated with the RUDP. A substantial increase in LST by 0.17 °C was observed associated with transformation of vegetation to artificial surfaces. An effective decrease in LST by −0.21 °C was observed over the opposite transition. Furthermore, sensitivity analysis suggested that LST fluctuations are affecting the % of CO2 emission. The current findings can assist policymakers in revisiting their policies to promote ecological conservation and sustainability in urban planning.

Genotypic variation in water relations and gas exchange of urban trees in Detroit, Michigan, USA

Increasing tree species diversity has become a key underpinning for communities to improve resilience of urban and community forests. Increasingly, urban forestry researchers are examining physiological traits to aid in selecting trees for urban sites. Knowledge of physiological responses also has implications for understanding species’ resilience to increased stresses associated with climate change. Here, we compare growth, leaf SPAD chlorophyll index, water relations, and gas exchange of seven genotypes of shade trees planted in two locations in downtown Detroit, MI, USA. Genotypes included Redpointe® maple (Acer rubrum ‘Frank Jr.’), Flashfire® maple (Acer saccharum ‘JFS-Caddo2′), Pacific Sunset® maple (Acer truncatum x platanoides ‘Warrenred’), Emerald City® tulip tree (Liriodendron tulipifera ‘JFS-Oz’), Chanticleer® pear (Pyrus calleryana ‘Glen’s Form’), swamp white oak (Quercus bicolor), and Emerald Sunshine® elm (Ulmus propinqua ‘JFS-Bieberich’). Trees were planted in either Lafayette Plaisance Park (Park), a large urban greenspace, or on the median of St. Aubin Avenue (Median), a nearby major thoroughfare. Tree height growth and leaf SPAD index were higher for trees planted in the Park location than on the Median. However, genotypic variation was larger than the effects of location or the interaction of Genotype × Location for most traits. Across measurement dates, midday leaf water potential was lowest for Pyrus trees and highest for Ulmus and Liriodendron trees. Pyrus and Quercus trees had relatively high rates of net photosynthesis (A) and stomatal conductance (gs) while Liriodendron, Acer saccharum, and Ulmus trees had low rates of A and gs. Liriodendron trees closed their stomata rapidly as leaf water potential (Ψw) declined (isohydric response), while Pyrus and Quercus trees maintained gs across a range of leaf Ψw (anisohydric response). Liriodendron trees also had the highest relative growth rates, suggesting that drought stress avoidance through isohydry is a viable drought tolerance mechanism in urban trees.

Physiological responses to water stress and stress memory in Argania spinosa

Drought stress is one of the major abiotic stress factors shifting the physiology and metabolism of the plants. In semiarid areas, drought stress events are often recurrent, and plants have developed strategies to remember a first so-called priming stress to eventually respond more effectively to a second triggering stress.In this study, we tested several physiological and morphological variables in Argania spinosa (L.) Skeels plants, growing in greenhouse conditions under a drought treatment induced by water withholding. Two sequential one-month periods of water stress were imposed to understand the stress memory events in this species The plants were divided into two groups depending on the treatment applied (irrigated and stressed) which later, after one month of a recuperation phase, were divided again into two more groups (having a total of four at the end of the study). Leaf samples were periodically taken and relative water content, gas exchange, chlorophyll content and other variables were measured, analysed and compared between those groups. Plants, which have suffered the two sequential water stress periods, were more affected according to several variables than plants subjected to only one stress treatment, so we finally conclude that this species does not seem to have any drought stress memory mechanisms for the studied variables, under the conditions of this experiment.

Consistent responses to moisture stress despite diverse growth forms within mountain fynbos communities

Understanding climate change impacts on the Cape Floristic Region requires improved knowledge of plant physiological responses to the environment. Studies examining physiological responses of mountain fynbos have consisted of campaign-based measurements, capturing snapshots of plant water relations and photosynthesis. We examine conclusions drawn from prior studies by tracking in situ physiological responses of three species, representing dominant growth forms (proteoid, ericoid, restioid), over 2 years using miniature continuous sap flow technology, long-term observations of leaf/culm water potential and gas exchange, and xylem vulnerability to embolism. We observed considerable inter-specific variation in the timing and extent of seasonal declines in productivity. Shallow-rooted Erica monsoniana exhibited steep within-season declines in sap flow and water potentials, and pronounced inter-annual variability in total daily sap flux (Js). Protea repens showed steady reductions in Js across both years, despite deeper roots and less negative water potentials. Cannomois congesta—a shallow-rooted restioid—was least negatively impacted. Following rehydrating rain at the end of summer, gas exchange recovery was lower in the drier year compared with the normal year, but did not differ between species. Loss of function in the drier year was partially accounted for by loss of xylem transport capacity in Erica and Cannomois, but not Protea. Hitherto unseen water use patterns, including inter-annual variability of gas exchange associated with contrasting water uptake properties, reveal that species use different mechanisms to cope with summer dry periods. Revealing physiological responses of key growth forms enhances predictions of plant function within mountain fynbos under future conditions.

Ácido salicílico atenua os efeitos do estresse salino sobre a morfofisiologia do cajueiro anão precoce

ABSTRACT Brazil is one of the largest cashew producers in the world, and its Northeast region stands out. However, cashew growth and development are negatively affected by irrigation with brackish water in its production. In this context, strategies have been employed to alleviate salt stress effects on plants. Among the strategies, the exogenous application of elicitor substances, such as salicylic acid, has stood out. Given the above, the objective of the present study was to evaluate the effect of foliar application of salicylic acid as an attenuator of salt stress on the morphophysiology of early dwarf cashew. The study was carried out in a greenhouse, in a randomized block design, in a 5 × 4 factorial arrangement, with five levels of electrical conductivity of the irrigation water - ECw (0.4, 1.2, 2.0, 2.8, and 3.6 dS m-1) and four concentrations of salicylic acid - SA (0, 1, 2, and 3 mM), with three replicates and one plant per plot. Irrigation with water of electrical conductivity above 0.4 dS m-1 negatively affected the leaf relative water content, gas exchange, photosynthetic pigments, and growth of plants. Salicylic acid at a concentration of 1 mM attenuated the effects of salt stress on electrolyte leakage, relative water content, gas exchange, synthesis of photosynthetic pigments, and growth of early dwarf cashew irrigated using water with ECw of up to 3.6 dS m-1, at 210 days after transplanting.

Riverine CO2 variations in permafrost catchments of the Yangtze River source region: Hot spots and hot moments

Rivers and streams are pivotal modulators in regional and global carbon cycles, but riverine CO2 flux is still uncertain for permafrost watersheds. Here we present the seasonal CO2 partial pressure (pCO2) and CO2 emission flux (FCO2) of 8 rivers and streams in the Yangtze River source region (YRSR), which have high permafrost coverage and seasonally thawed active layer. The YRSR rivers and streams are generally supersaturated with CO2, although there are a few sites with CO2 undersaturation during spring. The small headwater streams are CO2 hot spots that show significantly higher pCO2 (52 % higher) and FCO2 (792 % higher) than larger rivers. Both pCO2 and FCO2 show distinct seasonality across the study sites. pCO2 and FCO2 peak in summer and exhibit much lower levels in autumn and spring, indicating that hot moments of riverine CO2 occur in summer. Seasonal pCO2 and FCO2 variations are jointly controlled by hydrology, active layer dynamics and associated processes. The warm summer causes active layer thaw and highly active soil respiration, which release a large quantity of soil carbon and increase the CO2 sources via strengthened hydrologic connectivity. The high rainfall and more thaw-released water in summer bring high discharge, which can increase the water velocity and gas exchange rate and thus CO2 emission flux. Most of the variances of seasonal FCO2 (95 %) can be explained by hydrology and active layer thaw depth. Nevertheless, the hydrological process and seasonally thawed active layer over Qinghai-Tibet Plateau (QTP) play crucial roles in riverine carbon export due to the summer monsoon-dominated climate in QTP. Our results suggest that full seasonal coverage of CO2 dynamics is essential to quantify the annual CO2 flux accurately. Changing climate and warming permafrost may alter the annual CO2 emission due to deeper flow paths, hydrology changes, and longer emission windows throughout the year.

Acute and Rapid Response of Melissa officinalis and Mentha spicata to Saline Reclaimed Water in Terms of Water Relations, Hormones, Amino Acids and Plant Oxylipins.

The use of reclaimed water is considered an efficient tool for agricultural irrigation; however, the high salinity associated to this water could compromise plant quality and yields. Balm and spearmint plants were submitted for 15 days to three irrigation treatments in a controlled chamber: control with EC: 1.2 dS m-1 (control), reclaimed water from secondary effluent (EC: 1.6 dS m-1) (S) and water from secondary effluent with brine (EC: 4.4 dS m-1) (SB). The plant water status, stomatal and hormonal regulation, nutritional response, concentration of amino acids and plant oxidative stress-based markers, as well as growth were evaluated. Both species irrigated with saline reclaimed water reduced leaf water potential and gas exchange in comparison with control plants, following 2 days of exposure to irrigation treatments. Nevertheless, spearmint plants recovered photosynthetic activity from the seventh day onwards, maintaining growth. This was attributed to hormonal changes and a greater accumulation of some amino acids and some plant oxylipins (phytoprostanes) in comparison to balm plants, which contributed to the improvement in the organoleptic and health-promoting properties of spearmint. A longer irrigation period with saline reclaimed water would be necessary to assess whether the quality of both species, especially spearmint, could further improve without compromising their growth.

COP1 mutation causes low leaf temperature under various abiotic stresses in Arabidopsis thaliana.

Stomata are microscopic pores on epidermal cells of leaves and stems that regulate water loss and gas exchange between the plant and its environment. Constitutive photomorphogenic 1 (COP1) is an E3 ubiquitin ligase that is involved in plant growth and development and multiple abiotic stress responses by regulating the stability of various target proteins. However, little is known about how COP1 controls stomatal aperture and leaf temperature under various environmental conditions. Here, we show that COP1 participates in leaf temperature and stomatal closure regulation under normal and stress conditions in Arabidopsis. Leaf temperature of cop1 mutants was relatively lower than that of wild type (WT) under drought, salt, and heat stress and after abscisic acid (ABA), CaCl2, and H2O2 treatments. However, leaf temperature was generally higher in both WT and cop1 mutants after abiotic stress and chemical treatment than that of untreated WT and cop1 mutants. Stomatal aperture was wider in cop1 mutants than that in WT under all conditions tested, although the extent of stomatal closure varied between WT and cop1 mutants. Under dark conditions, leaf temperature was also lower in cop1 mutants than that in WT. Expression of the genes encoding ABA receptors, ABA biosynthesis proteins, positive regulators of stomatal closure and heat tolerance, and ABA-responsive proteins was lower in cop1 mutants that that in WT. In addition, expression of respiration-related genes was lower in cop1 mutants that that in WT. Taken together, the data provide evidence that mutations in COP1 lead to wider stomatal aperture and higher leaf temperature under normal and stress conditions, indicating that leaf temperature is highly correlated with stomatal aperture.

Nickel toxicity alters growth patterns and induces oxidative stress response in sweetpotato.

Nickel (Ni) contaminated soil is a persistent risk to plant growth and production worldwide. Therefore, to explore the Ni toxicity levels in sweetpotato production areas, we investigated the influence of different Ni treatments (0, 7.5, 15, 30, and 60 mg L-1) for 15 days on phenotype, Ni uptake, relative water content, gas exchange, photosynthetic pigments, oxidative stress, osmolytes, antioxidants, and enzymes of sweetpotato plants. The results presented that Ni at higher levels (30 and 60 mg L-1) substantially reduced growth, biomass, and root morphological traits. The Pearson correlation analysis suggested that Ni toxicity causes oxidative injuries as persistent augmentation of hydrogen peroxide (H2O2) and malonaldehyde (MDA) and reduced RWC, gas exchange, and photosynthetic pigment. Furthermore, this study revealed that sweetpotato could tolerate moderate Ni treatment (up to 15 mg L-1) by reducing oxidative stress. The results also indicated that the increase in the activities of mentioned osmolytes, antioxidants, and enzymes is not sufficient to overcome the higher Ni toxicity. Based on these results, we suggest using low Ni-contaminated soil for better growth of sweetpotato and also could be used as a phytoremediator in moderate Ni-contaminated soil.

Differential Physiological Traits, Ion Homeostasis and Cane Yield of Sub-Tropical Sugarcane Varieties in Response to Long-Term Salinity Stress

Sugarcane grown under a wide range of agro-climatic conditions accounts for ~80% of the sugar production worldwide. Since sugarcane productivity is severely affected by abiotic stresses and hence, an experiment was conducted for two consecutive years during 2020 and 2021 on popular sub-tropical sugarcane varieties. The experiment was laid out in two-factorial RBD consisting of nine sugarcane genotypes (Co 98014, Co 0118, Co 0238, Co 05011, Co 06034, Co 09022, Co 12029, Co 15023 and Co 15027) and salinity treatments (Control, ECiw ~ 4, 8 and 12 dS m−1) in 5 replications. Two budded setts were planted in pots and irrigated with saline water of respective levels till formative phase and observed the build-up in electrical conductivity of soil extract (ECse) from 0.48 (control) to 2.99, 4.81 and 7.08; while further saline irrigation increased the ECse values to 4.48, 6.24 and 9.33 dS m−1 in treatments ECiw ~ 4, 8 and 12 dS m−1, respectively. Increase in soil EC decreased plant survival by 24.1, 47.0 and 79.6% under continued irrigation of ECiw ~ 4, 8, 12 dS m−1 with respect to control. Continued saline irrigation caused significant reduction in growth, which was associated with reduction in relative water content (RWC) and gas exchange traits. RWC decreased by 4.91 to 21.9%, chlorophyll content by 8.46 to 32.75%, photosynthetic rate (Pn) by 16.85 to 91.44%, stomatal conductance by 14.96 to 84.25%, transpiration rate by 14.13% to 89.8% and chlorophyll fluorescence by 5.33 to 42.67% from ECiw ~ 4 to 12 dS m−1, respectively. Significant variations in Na+ and K+ ion content was observed under elevated saline condition in roots, leaves and juice extract of genotypes. Na+/K+ ratio, an important trait for screening salinity tolerance, increased in all genotypes as compared to control, the increase was predominant in susceptible varieties. Single cane weight (SCW) was drastically affected by saline irrigation, with a reduction of 36.4, 68.5 and 83.5% at ECiw ~ 4, 8 and 12 dS m−1, respectively as compared to control, with similar declining trend in juice quality. Based on our results, Co 0238, Co 0118 and Co 98014 were tolerant to salinity stress by maintaining higher Pn, lower leaf Na+/K+ ratio, higher SCW and higher juice sucrose content.

Water relations and gas exchange in <i>Ruilopezia atropurpurea</i> (Asteraceae), a giant rosette growing under contrasting microclimates in the high tropical Andes

Tropical high andean ecosystems, known as paramos, are unique because they are highly diverse, have a high number of endemic species, and play an essential role in different ecosystem services, but are especially susceptible to climate change. Most of the giant rosettes, a dominant growth-form in the paramos, depend on unique features like stems protected by marcescent leaves, voluminous stem pith, and leaf pubescence. However, Ruilopezia atropurpurea lacks these characteristics and must respond differently to endure the paramo extreme conditions. Additionally, unlike other rosettes, this species is found under contrasting exposed and understory microenvironments so that intraspecific plasticity is also expected. We evaluated the responses of R. atropurpurea in terms of leaf water relations, gas exchange, and morphological characteristics in temporal (seasonal and daily variations) and spatial (microsite differences) scales in a Venezuelan paramo. R. atropurpurea displayed lower leaf water potentials (minimum leaf water potentials of -1.5 MPa and -1.8 MPa at the turgor loss point), higher leaf conductance (620 mmol m-2s-1), transpiration (5 molm-2s-1), and CO2 assimilation (13 mmol m-2s-1) rates compared to other paramo giant rosettes. A reduction in leaf area and specific leaf area occurred from understory to exposed sites. R. atropurpurea diverges from the typical responses of most paramo giant rosettes to the extreme environmental conditions. This species’ morphological and physiological plasticity permits it inhabit under variable microclimatic conditions, but despite its confirmed plasticity, it is not able to reach higher elevations as other giant rosettes successfully have.

Estimation of gas exchange coefficients from observations on the Yenisei River, Russia

AbstractThe gas exchange between water bodies and air is difficult to measure, thus the approximations of air–water gas exchange coefficient based solely on wind speed has been widely used. However, such approaches may not work well in river environments. In rivers, water currents may govern gas exchange. Thus, a new approximation for calculating the gas exchange coefficient (k) based on the near‐surface velocity scale (us) is suggested and compared to wind‐based estimates. Our velocity scale estimates are based on field observations during summer 2016 on the Yenisei River using an Acoustic Doppler Current Profiler, high‐frequency temperature profilers and a vessel‐mounted meteorological sensors‐suite. The results demonstrate that us‐derived gas exchange coefficients are higher than those based solely on wind speed. The results demonstrate that the wind approximation underestimates gas exchange coefficients during low‐wind conditions.

Establishment of argan tree plantlets (Argania spinosa (L.) Skeels) grown from generative and vegetative propagation under different watering regimes at the nursery stage

The ongoing efforts to rehabilitate the argan tree (Argania spinosa (L.) Skeels) woodland have prompted pertinent socio-economic reconsiderations. However, its reserve biosphere is experiencing an escalating deterioration pace. To satisfy the economic and ecological requirements, accurate in vitro and ex vitro propagation protocols were suggested. However, the physiological state of the plantlets remains less investigated. Hence, this study aims to evaluate the physiological response of argan tree plantlets propagated from different stem cuttings compared to seedlings under two watering regimes at the nursery stage. The cuttings establishment was similar to the seedlings in terms of water uptake, transpiration rate (E), stomatal conductance (gs), and net photosynthesis (A). The plantlet's height, foliation, and stomatal density were significantly influenced by the type of propagation (P < 0.01). The seedlings exhibited better growth performances in height and foliation with 28.0 ± 9.9 cm and 79.6 ± 21.6 leaves per plantlet, respectively. The seedlings were followed by herbaceous, semi-woody, and woody cuttings. Remarkably, the seedlings' foliation was 38%, 68%, and three-fold higher than the cuttings. The woody cuttings were recalcitrant. However, their plantlets exhibited the highest stomatal densities with 140.3 stomata.mm−2. Concerning the watering regime, both field capacities, 100% FC and 120% FC, allowed the establishment of the plantlets. Nevertheless, there were no significant differences regarding water uptake, foliation, stomatal density, and gas exchange. Remarkably, 120% FC has facilitated the plantlets' growth. Through these, the best establishment of argan tree plantlets from herbaceous cuttings under a 120% FC watering regime is currently obtained at the nursery stage.