Leaf Relative Water Research Articles

CO2 Elevation and Nitrogen Supply Alter the Growth and Physiological Responses of Tomato and Barley Plants to Drought Stress

Global climate change will modify plants in terms of growth and physiology. To better understand the consequences of this effect, the responses of the leaf water relations and nitrogen (N) use efficiency of barley and tomato plants to elevated CO2 (e[CO2], 800 ppm) combined with progressive drought stress at two levels of N supply (N1, 0.5 g N pot−1 and N2, 1.0 g N pot−1) were studied. The plants were grown in two separate phytotrons at ambient CO2 (a[CO2], 400 ppm) and e[CO2], respectively. The leaf physiological parameters as well as carbon (C) and N concentrations were determined; plant growth, water and N use efficiencies were evaluated. The results showed that e[CO2] increased photosynthesis and water use efficiency (WUE) while decreased specific leaf area (SLA) in both species, whereas N supply level differentially influenced WUE in barley and tomato plants. The abscisic acid (ABA)-induced stomatal closure during progressive soil drying varied between the two species where the stomatal conductance (gs) of barley plants was more sensitive to leaf ABA than tomato plants, though CO2 environment did not affect the response in both species. Compared to a[CO2], e[CO2] reduced plant transpiration rate (Tplant) in barley but not in tomato. e[CO2] increased the leaf C:N ratio ([C:N]leaf) in plants by enhancing leaf C concentration ([C]leaf) in barley and by dilution of leaf N concentration ([N]leaf) in tomato, respectively, but N2 substantially decreased [C:N]leaf, and thus, N treatment was the dominant factor controlling [C:N]leaf. Collectively, appropriate N supply may modulate the acclimation of plants to e[CO2] and soil water deficits. This study provides some novel insights into N management of different plant species for adapting to future drier and CO2-enriched environment.

Effect of potassium and magnesium application on growth, yield and nutrient uptake of rainfed maize in the sub-montaneous region of Punjab, India

Potassium (K) and magnesium (Mg) are essential plant macronutrients responsible for mitigation of biotic and abiotic stresses as well as enhancement in yield of maize. In rainfed maize, low productivity due to imbalanced use of fertilizers, erratic rainfall and periodic dry spells are major constraints. Hence, a field experiment was conducted in rainy season during 2015, 2016 and 2017 on an Inceptisol to optimize the levels of K and Mg in rainfed maize. The experiment consisted of four levels of K; control, K @20 kg ha−1, K@30 kg ha−1 and K 40 kg ha−1 and four levels of Mg; control, Mg@15 kg ha−1, Mg@30 kg ha−1, and Mg@45 kg ha−1. Application of K and Mg improved leaf area Index, chlorophyll content and relative water content in maize. Yield attributes of maize also improved significantly with application of K and Mg over control. Highest grain yield (3205 and 3169 kg ha−1) was recorded with the application of 40 kg K ha−1and 45 kg Mg ha−1, respectively which was at par with 30 kg K ha−1 (3103 kg ha−1) and 30 kg Mg ha−1 (3106 kg ha−1), respectively. The highest net returns (US $347 ha−1) and BC ratio (1.72) was recorded with 40 kg K ha−1 while application of 30 kg Mg ha−1 recorded highest net returns (US $332 ha−1) and BC ratio (1.71). Application of 30 kg K ha−1 and 30 kg Mg ha−1 was found to be optimum to improve growth, yield and nutrient uptake in rainfed maize.

Variation in cloud immersion, not precipitation, drives leaf trait plasticity and water relations in vascular epiphytes during an extreme drought.

Epiphytes are abundant in ecosystems such as tropical montane cloud forests where low-lying clouds are often in contact with vegetation. Climate projections for these regions include more variability in rainfall and an increase in cloud base heights, which would lead to drier conditions in the soil and atmosphere. While recent studies have examined the effects of drought on epiphytic water relations, the influence that atmospheric moisture has, either alone or in combination with drought, on the health and performance of epiphyte communities remains unclear. We conducted a 10-week drought experiment on seven vascular epiphyte species in two shadehouses, one with warmer and drier conditions and another that was cooler and more humid. We measured water relations across control and drought-treatment groups and assessed functional traits of leaves produced during drought conditions to evaluate trait plasticity. Epiphytes exposed to drought and drier atmospheric conditions had a significant reduction in stomatal conductance and leaf water potential and an increase in leaf dry matter. Nonsucculent epiphytes from the drier shadehouse had the greatest shifts in functional traits, whereas succulent epiphytes released stored leaf water to maintain water status. Individuals in the drier shadehouse had a substantial reduction in performance, whereas drought-treated individuals that experienced cloud immersion displayed minimal changes in water status. Our results indicate that projected increases in the cloud base height will reduce growth and performance of epiphytic communities and that nonsucculent epiphytes may be particularly vulnerable.

Selection of Some Plant Species Suitable for Green Belt Expansion in Mumbai Industrial Area - A Baseline to Alleviate Global Air Pollution

The air quality and global environment is immensely affected due to the industrial as well as urban expansion. The present study aims to identify the natural tolerance of six plant species towards the air pollution, which are growing along the Chembur industrial area of Mumbai. The plant’s air pollution tolerance level was identified by evaluating Air Pollution Tolerance Index (APTI) and Anticipated Performance Index (API). The estimation of APTI was done based on the measurement of physico-chemical parameters like pH, ascorbic acid, total chlorophyll content and the relative leaf water content of the fresh leaves of plant species grown along the industrial and non-industrial areas. The higher API values obtained for the Thespesia populnea (L.) Sol. excorrea, Polyalthia longifolia and Albizia saman (Jacq.) Merr plant species growing in the industrial zone indicate a good tolerance towards polluted air and hence are suggested for green zone development in the Chembur industrial area. The present work can be extended for the selection of the most air pollution tolerant plant species for the development of green zone along the industrial belt across the world. It will facilitate healthy atmosphere for the nearby population.

Phosphorus confers tolerance against manganese toxicity in Prunus persica by reducing oxidative stress and improving chloroplast ultrastructure

In this study, we evaluated the mitigative role of phosphorus (P) in terms of manganese (Mn) toxicity in peach (Prunus persica L.) plants. Ten-day-old seedlings were treated with excess Mn (1 mM MnSO4) alone and in combination with different P levels (100, 150, 200 and 250 μM KH2PO4) in half-strength Hoagland medium. The results demonstrated that Mn toxicity plants accumulated a significant amount of Mn in their tissues, and the concentration was higher in roots than in leaves. The accumulated Mn led to a considerable reduction in plant biomass, water status, chlorophyll content, photosynthetic rate, and disrupted the chloroplast ultrastructure by increasing oxidative stress (H2O2 and O2•−). However, P supplementation dramatically improved plant biomass, leaf relative water and chlorophyll contents, upregulating the ascorbate-glutathione pool and increasing the activities of antioxidant enzymes (superoxide dismutase; peroxidase dismutase; ascorbate peroxidase; monodehydroascorbate reductase; dehydroascorbate reductase), thus reducing oxidative damage as evidenced by lowering H2O2 and O2•− staining intensity. Moreover, P application markedly restored stomatal aperture and improved chloroplast ultrastructure, as indicated by the improved performance of photosynthetic machinery. Altogether, our findings suggest that P (250 μM) has a great potential to induce tolerance against Mn toxicity by limiting Mn accumulation in tissues, upregulating antioxidant defense mechanisms, alleviating oxidative damage, improving chloroplast ultrastructure and photosynthetic performance in peach plants.

Leaf 13C and 15N composition shedding light on easing drought stress through partial K substitution by Na in eucalyptus species

This work aimed to investigate the partial K-replacement by Na supply to alleviate drought-induced stress in Eucalyptus species. Plant growth, leaf gas exchange parameters, water relations, oxidative stress (H2O2 and MDA content), chlorophyll concentration, carbon (C) and nitrogen (N) isotopic leaf composition (δ13C and δ15N) were analyzed. Drought tolerant E. urophylla and E. camaldulensis showed positive responses to the partial K substitution by Na, with similar dry mass yields, stomatal density and total stomatal pore area relative to the well K-supplied plants under both water conditions, suggesting that 50% of the K requirements is pressing for physiological functions that is poorly substituted by Na. Furthermore, E. urophylla and E. camaldulensis up-regulated leaf gas exchanges, leading to enhanced long-term water use efficiency (WUEL). Moreover, the partial K substitution by Na had no effects on plants H2O2, MDA, δ13C and δ15N, confirming that Na, to a certain extent, can effectively replace K in plants metabolism. Otherwise, the drought-sensitive E. saligna species was negatively affected by partial K replacement by Na, decreasing plants dry mass, even with up-regulated leaf gas exchange parameters. The exclusive Na-supplied plants showed K-deficient symptoms and lower growth, WUEL, and δ13C, besides higher Na accumulation, δ15N, H2O2 and MDA content.

Effects of elevated CO2 and nitrogen supply on leaf gas exchange, plant water relations and nutrient uptake of tomato plants exposed to progressive soil drying

The effects of nitrogen (N) supply on the response of leaf gas exchange, leaf water relations and plant nutrient uptake of tomato plants exposed to progressive soil drying under elevated CO2 (e[CO2], 800 ppm) were investigated. Two tomato genotypes differing in their endogenous abscisic acid (ABA) level, i.e. Ailsa Craig and its ABA-deficient mutant (flacca) were grown in pots in greenhouse cells with either ambient CO2 (a[CO2], 400 ppm) or e[CO2]. Two N levels, i.e., N1, 0.5 g pot−1 and N2, 1.0 g pot−1 were used and the N fertilizer (NH4NO3) was applied with the irrigation water before transplanting. The results showed that e[CO2] and N2 increased photosynthesis and water use efficiency (WUE) of tomato plants. N2 improved plant water relations by sensitizing the decline of transpiration rate during soil drying. The plant N acquisition and major ionic concentrations in xylem sap were lowered under e[CO2], such negative effect was compensated by increasing N supply. For WT, the ABA concentrations in leaf ([ABA]leaf) and xylem sap ([ABA]xylem) were increased with the decrease of the fraction of transpirable soil water, whereas, for flacca this was only observed in [ABA]leaf. Compared to WT, flacca had lower xylem sap ionic concentrations and WUE. Collectively, the responses of tomato plants to e[CO2] and N supply under progressive soil drying were genotypic-dependent, and endogenous ABA level could play an important role in modulating the responses.

Adjustments in photosynthesis and leaf water relations are related to changes in cell wall composition in Hordeum vulgare and Triticum aestivum subjected to water deficit stress

In the current climate change scenario, understanding crops’ physiological performance under water shortage is crucial to overcome drought periods. Although the implication of leaf water relations maintaining leaf turgor and stomatal functioning under water deprivation has been suggested, the relationships between photosynthesis and osmotic and elastic adjustments remain misunderstood. Similarly, only few studies in dicotyledonous analysed how changes in cell wall composition affected photosynthesis and leaf water relations under drought. To induce modifications in photosynthesis, leaf water relations and cell wall composition, Hordeum vulgare and Triticum aestivum were subjected to different water regimes: control (CL, full irrigation), moderate and severe water deficit stress (Mod WS and Sev WS, respectively). Water shortage decreased photosynthesis mainly due to stomatal conductance (gs) declines, being accompanied by reduced osmotic potential at full turgor (πo) and increased bulk modulus of elasticity (ε). Whereas both species enhanced pectins when intensifying water deprivation, species-dependent adjustments occurred for cellulose and hemicelluloses. From these results, we showed that πo and ε influenced photosynthesis, particularly, gs. Furthermore, the (Cellulose+Hemicelluloses)/Pectins ratio determined ε and mesophyll conductance (gm) in grasses, presenting the lowest pectins content within angiosperms. Thus, we highlight the relevance of cell wall composition regulating grasses physiology during drought acclimation.

Physiological Variations in Cucurbita moschata Duch. Ex. Poir Due to a Nigerian Strain of Moroccan Watermelon Virus: Lagenaria breviflora Isolate

Aim: Physiological variations in Cucurbita moschata due to infection with a Nigerian strain of Moroccan watermelon virus (MWMV): Lagenaria breviflora isolate was studied.
 Study Design: Randomized block design was used.
 Place and Duration of Study: Botany Department, University of Calabar, Calabar, Nigeria between March and May, 2015.
 Methodology: Seeds of C. moschata were sown, on germination inoculated with the virus and analyzed for possible variations between healthy and inoculated plants.
 Results: Results analysis revealed increase in all amino acids investigated. Highest significant (P=0.05) percentage variation in amino acids of inoculated and healthy were -40.0% for aspartic acid, -36.1% (histidine), -29.7% (proline), -28.8% (lysine), -23.3% (glysine), -16.6% (phenylalanine) and -12.6% (glutamic acid). Infection of C. moschata with a Nigerian Strain of MWMV: Lagenaria breviflora isolate caused significant decrease in leaf nitrogen and relative water content of inoculated plants compared to the healthy. Highest percentage decrease in leaf nitrogen was 40.7% at 2 weeks after inoculation (WAI) and lowest of 25.0% at 10 WAI. The virus caused decrease in relative water content of 29.6% at 6 WAI. Activity of oxidative stress enzymes: peroxidase (POD) and polyphenol oxidase (PPO) and enzymes of the oxidative pentose phosphate pathway: glucose-6-phosphate dehydrogenase (6PGdH) and 6-phosphogluconic acid dehydrogenase (G6PdH) were significantly (P=0.05) increased in infected C. moschata- MWMV plant. Enzymes activity was significantly higher in inoculated than in healthy plants at all stages of growth with decrease at later periods for both inoculated and healthy plants. Percentage increase in POD, PPO, G6PdH and 6PGdH activity due to infection at 8 WAI had values of -40.5%, -46.7%, -98.9% and -89.1% respectively.
 Conclusion: The Nigerian strain of MWMV: Lagenaria breviflora isolate caused significant variations with increase and decrease in biochemical and physiological components of C. moschata affecting its growth and yield.

Study on Spatial and Seasonal Variation in APTI of Tree Species along Roads of Shivalik Foothills in Himachal Pradesh

The present study was conducted during the year 2018-2019 to determine the impact of road on Air Pollution Tolerance Index (APTI) of plants growing along the road. A comparative study was done between three roads viz., National highway, State highway and Link Road. Among three roads, link road can be considered as control because vehicular emissions were minimal or non-existent. Three plants (Dalbergia sisso, Mangifera indica and Ficus palmata) were selected as per their uniform presence along all three roads. Four biochemical parameters viz., ascorbic acid, total chlorophyll, leaf extract pH and relative water content were used to calculate the air pollution tolerance index. Season wise maximum ascorbic acid, leaf extract pH and relative water content was observed during post monsoon season whereas total chlorophyll content was observed during pre monsoon season. The APTI of the selected plant species ranged from 8.23 to 10.76 during pre-monsoon and 9.03 to 11.09 during post-monsoon. Anticipated Performance Index (API) was in order of Mangifera indica with highest API grade (6) and it was excellent among plants followed by Dalbergia sisso (5) in very good and Ficus palmata (3) in moderate. Student t-test analysis of seasonal variation of biochemical parameters in leaf of selected tree species was carried out and it was observed that there was significant seasonal effect on mean values of ascorbic acid content and APTI whereas there was no impact of seasons on total chlorophyll content, leaf extract pH and relative water content.

Comparative study of roadside avenue trees as bio-indicators of air pollution in and around Mumbai, India: A case study

With rapid increase in urbanization followed by industrialization compounded due to ever-exploding population in the past few decades there is a steep rise in contamination of one of the most vital abiotic factors of the environment i.e., the air. In these circumstances, the clean and green measures to monitor and control air pollution have become inevitable. Air Pollution Tolerance Index (APTI) is one such index for indicating the extent of the plants to withstand air pollution. This includes analysis of physiological and biochemical parameters like total chlorophyll content, ascorbic acid content, pH of the leaf extract and relative water content of the leaves. In this study, the plants selected are mature tree species like Polyalthia longifolia, Putranjiva roxburghii, Alstonia scholaris, Delonix regia and Peltophorum pterocarpum from Mumbai and its surrounding regions. According to the Air Pollution Tolerance Index (APTI) values, plants can be classified as tolerant, intermediate, sensitive and highly sensitive. The tolerance of the plants studied in the decreasing order is as follows P. roxburghii > P. pterocarpum > D. regia > P. longifolia > A. scholaris. Species selected on the basis of their APTI values can then be used as bio-indicators of air pollution and in its mitigation for green belt development in urban areas.

EFFECT OF VEHICULAR EMMISSION ON SOME BIOCHEMICAL PARAMETERS AND STOMATA OF SELECTED TREES ALONG ZARIA-KADUNA HIGHWAY

Biochemical and stomatal studies were conducted on selected trees along Zaria-Kaduna highway to determine their pollution tolerance level. The sites were chosen to emphasize exposure to vehicular emission pollution (VEP) and non-exposure to vehicular emission pollutants (NEP). Biochemical parameters analyzed where based on the Air Pollution Tolerance Index (APTI) which prioritizes four biochemical parameters, namely ascorbic acid, total chlorophyll, leaf extract pH and relative water content (RWC), for pollution tolerance. Ascorbic acid and RWC were higher in plants at the polluted site with Mangifera indica showing the highest increase of 1.2mg/g while total chlorophyll decreased most significantly in Ficus polita of about 4.1mg/g. Results from stomata studies reveal a significant difference (P ≤ 0.05) in stomatal size and stomatal index for all the trees at the polluted sites. Stomata was generally found to significantly decrease in size or increase in density for plants at the polluted sites. Results computed for APTI show M. indica (24), Anarcardium occidentale (24.1), Eucalyptus cameldulensis (17.1) and Senna siamea (18.6) having the best APTI which indicate their possible tolerance to air pollution stress while Azadirachta indica (14.4), Ficus polita (13), G. arborea (9.4), T. catapa (15.2), Parkia biglobosa (13.4), and Tamarindus indica (9.9) were found to be sensitive. M. indica and A. occidentale had the best APTI indices which indicate that these plants could serve as sinks in absorbing air pollutants

Soil cadmium and lead affecting biochemical properties of Matricaria chamomilla L. at different growth stages in the greenhouse and field.

Heavy metals bioremediation by medicinal plants is an important research issue, which has yet to be investigated. Matricaria chamomilla accumulation of soil cadmium (Cd, 0, 10 and 40mg/kg) and lead (Pb, 0, 60 and 180mg/kg) affecting plant biochemical properties L. at different growth stages in the greenhouse and field was investigated. The 10-kg experimental pots (located in the greenhouse and field with 80% of field capacity moisture) were filled with the treated soils, and were planted with M. chamomilla L. seeds (three replicates). Plants were sampled to determine their biochemical properties including Cd and Pb contents, pigments, proline (Pro), leaf relative water (LRW), lipid peroxidation (LX), and superoxide dismutase (SOD, EC 1.15. 1.1), and catalase (CAT, EC 1.11.1.6) activities. Soil final concentration of Cd and Pb was also determined. Heavy metal stress significantly decreased plant pigment contents; however, it significantly increased plant PRO, LRW, LX and SOD, and not CAT. Heavy metal, growth stage, growth location, and their interactions significantly affected plant heavy metal concentrations. Interestingly, although significantly higher concentration of Cd was observed in plant aerial part under greenhouse conditions, plant roots had significantly higher concentrations of Cd under field conditions, and it was reverse for Pb. Increased concentration of Cd and Pb significantly enhanced plant Pro content and the highest one was resulted by Pb3 (913.46mg/g fresh weight) significantly higher than other treatments including Cd3 (595.34mg/g fresh weight). M. chamomilla is a suitable species for the bioremediation of soils polluted with Cd and Pb.

Mycorrhizal mixtures affect the growth, nutrition, and physiological responses of soybean to water deficit

Drought stress has a negative impact on crop growth and productivity worldwide. Plant symbionts such as arbuscular mycorrhizal fungi (AMF) can enhance plant growth and improve plant resistance to drought stress. AMF mixture inocula and plant responses to drought still require further study. The objective of this study was to investigate the effects of non-inoculation (NM) or inoculation with three commercial AMF inocula containing a single or mixtures comprising different numbers of AMF species: M1 (Rhizophagus intraradices), M2 (Rhizophagus clarus, R. intraradices, Septoglomus deserticola, Funneliformis mosseae), and M3 (Rhizophagus intraradices, R. aggregatum, Funneliformis mosseae, Olaroideoglomus etunicatum) on growth, nutritional, and physiological responses of soybean (Glycine max L. cv. Hutcheson) grown in a greenhouse under different water stress levels [WW = well watered (90% FC), MS = medium (60% FC) and SS = severe stressed (30% FC)]. The AMF-inoculated plants had significantly higher plant biomass, chlorophyll content, stomatal conductance, leaf water relations, and mineral contents in comparison to NM plants. Applied mycorrhizal inocula differed in their response to water-deficit conditions. M2 inoculant generally supported greater plant biomass, stomatal conductance, leaf water content, and leaf N, P, K, S, Mn, and Cu contents than M1 and M3 inocula, especially under MS and SS treatments. These results indicated that all mycorrhizal inocula supported plant growth both generally and with soil water deficit; however, M2-inoculated plants performed better than M1 and M3 under drought stress. Therefore, mycorrhizal inocula are effective for supporting soybean growth and offsetting the effects of drought and AMF technology that can support sustainable crop cultivation under soil water-deficit conditions. Different types of inocula have different effects, however, and thus require testing for individual crops.

Plant functional traits along an old-field succession in the high tropical andes

The páramo, a high tropical Andean ecosystem, presents very distinct climatic, floristic and ecological features. Paramo plants have adapted to pronounced daily temperature fluctuations, freezing temperatures any night of the year, high incoming radiation and seasonal unfavorable water availability conditions. Long fallow agricultural systems are common in the páramo, permitting partial recuperation of the vegetation through a secondary succession. Different hypothesis related to plant traits (water relations and gas exchange characteristics or biomass allocation patterns) during succession have been proposed. Particular traits have been associated to the stages along successional gradients from early species (traits related to high resource acquisition abilities) to late species (traits linked to internal conservation of resources). Our purpose was to study plant functional responses of different herbaceous species in an old-field succession in the high tropical Andes. Plant traits (specific leaf area (SLA), maximum CO2 assimilation rates (Amax), leaf nitrogen content (Nleaf), leaf water relations and biomass allocation) were studied in grasses and forbs along different successional stages. Clear trends in SLA, Amax on a mass basis, Nleaf and aboveground/belowground biomass allocation were found along the successional gradient for grasses, while patterns were not as well-defined for forbs in the latter two traits. No patterns in leaf water relations characteristics were observed for either plant-growth forms. Strategies associated to plant traits significantly influence plant species dominance and community assembly during secondary succession in tropical alpine open environments like the páramos. Plant traits linked to rapid growth (SLA, Amax and Nleaf) dominate during early succession. In contrast to previous studies, drought resistance traits were not found to dominate in late succession stages for either grasses or forbs.

Calcium improves the leaf physiology of salt treated Limonium stocksii: A floriculture crop

Calcium acts as a signaling molecule in many plants to improve resistance during unfavorable environments. Limonium stocksii (Boiss.) Kuntze seedlings were grown in 0 and 600 mmol L−1 NaCl (with and without additional 15 mmol L−1 Ca2+) for 15 d. The effects of these treatments were studied on plant growth, leaf water relations, malondialdehyde (MDA) content, ion-flux, Na+ secretion rate and photosynthesis. Plant biomass declined by 50% and MDA content increased by 50% in plants treated with 600 mmol L−1 NaCl for 15 d. Leaf water content (WCFM) and relative water content declined and sap osmolality increased after 3 d of 600 mmol L−1 NaCl treatment. Leaf Na+, Na+/K+ ratios and Na+ secretion rate were increased in salinity treatment. Decrease in photosynthesis was coupled with lower stomatal conductance and intercellular CO2, however, instantaneous water use efficiency was improved under salinity treatment. Efficiency of PSII, relative electron transport rate, photochemical quenching and non-photochemical quenching were reduced by salinity treatment compared to non-saline control. The Ca2+ application yielded 25% higher fresh mass at enhanced water contents while lowers tissue osmotic potential and membrane damage in plants exposed to high salinity. The Na+ accumulation in the leaf was reduced, while the secretion was increased in the presence of additional Ca2+. However, Ca2+ application did not improve either the photosynthetic gas exchange or light reactions of photosynthesis under saline conditions. Our results indicated that L. stocksii decreases its growth, water content, photosynthesis and dark respiration under increased leaf Na+ concentrations. Whereas, application of Ca2+ enhanced plant salinity resistance by improving water balance, Na+-secretion and membrane integrity.

Low-temperature acclimation and legacy effects of summer water deficits in olive freezing resistance.

Low temperatures and drought are the main environmental factors affecting plant growth and productivity across most of the terrestrial biomes. The objective of this study was to analyze the effects of water deficits before the onset of low temperatures in winter to enhance freezing resistance in olive trees. The study was carried out near the coast of Chubut, Argentina. Plants of five olive cultivars were grown outdoor in pots and exposed to different water deficit treatments. We assessed leaf water relations, ice nucleation temperature (INT), cell damage (LT50), plant growth and leaf nitrogen content during summer and winter in all cultivars and across water deficit treatments. Leaf INT and LT50 decreased significantly from summer to winter within each cultivar and between treatments. We observed a trade-off between resources allocation to freezing resistance and vegetative growth, such that an improvement in resistance to sub-zero temperatures was associated with lower growth in tree height. Water deficit applied during summer increased the amount of osmotically active solutes and decreased the leaf water potentials. This type of legacy effect persists during the winter after the water deficit even when treatment was removed by natural rainfalls.

Response of wheat varieties to salinity: growth, yield and ion analysis

In plants, development, growth and yield most severely affected through saline soil/water in growth medium, ultimately cause severe threat to global food production for human being. Wheat (Triticum aestivum) is the most edible crop in Pakistan. Production of this crop can be improved through using marginal areas with the help of growing salt-tolerant varieties. The present investigation is carried out to screen out six local wheat varieties (F.Sarhad, Insaf, Lalma, Tatora, Bathoor and Barsat) with reference to their vegetative and reproductive growth, different physiological parameters [relative water content (RWC), electrolyte-leakage (EL) and leaf water loss (LWL)] and ionic status of plants. Present experiment designed in completely randomized manner (CRD) and 54 pots were arranged in the Botanical Garden, Department of Botany. These pots arranged in 6 lines with 9 pots/line and each line was irrigated with non-saline (control), 50 mM and 150 mM NaCl solution. The data from present research revealed that application of salt cause significant reduction in plant-height, root-length, fresh-biomass, dry-biomass, seed number/plant, seed weight/plant, spike-weight, relative water content, leaf water loss, and different ions of plants. Similarly at same applied doses of salt weight of 100 seeds, spike-length, electrolyte-leakage, Na+ and Cl- ions become increased. It has been concluded from the results of present study that varieties F. Sarhad, Insaf and Lalma exhibited more salt tolerance as compare to other varieties. So, these recommended for growing on moderately salt affected soil/water to achieve more yield of wheat from such affected lands of Khyber Pakhtunkhwa, Pakistan.

Differential outcomes of novel plant-herbivore associations between an invading planthopper and native and invasive Spartina cordgrass species

Non-native plants may benefit, briefly or permanently, from natural enemy release in their invaded range, or may form novel interactions with native enemy species. Likewise, newly arrived herbivores may develop novel associations with native plants or, where their hosts have arrived ahead of them, re-establish interactions that existed previously in their ancestral ranges. Predicting outcomes from this diversity of novel and re-established interactions between plants and their herbivores presents a major challenge for invasion biology. We report on interactions between the recently arrived invasive planthopper Prokelisia marginata, and the multi-ploidy Spartina complex of four native and introduced species in Britain, each representing a different level of shared evolutionary history with the herbivore. As predicted, S. alterniflora, the ancestral host, was least impacted by planthopper herbivory, with the previously unexposed native S. maritima, a nationally threatened species, suffering the greatest impacts on leaf length gain, new leaf growth and relative water content. Contrary to expectations, glasshouse trials showed P. marginata to preferentially oviposit on the invasive allododecaploid S. anglica, on which it achieved earlier egg hatch, faster nymphal development, larger female body size and greatest final population size. We suggest P. marginata is in the process of rapid adaptation to maximise its performance on what is now the most abundant and widespread host in Britain. The diversity of novel and re-established interactions of the herbivore with this multi-ploidy complex makes this a highly valuable system for the study of the evolutionary ecology of plant–insect interactions and their influence on invasion dynamics.

Leaf water relations in epiphytic ferns are driven by drought avoidance rather than tolerance mechanisms.

Opportunistic diversification has allowed ferns to radiate into epiphytic niches in angiosperm dominated landscapes. However, our understanding of how ecophysiological function allowed establishment in the canopy and the potential transitionary role of the hemi-epiphytic life form remain unclear. Here, we surveyed 39 fern species in Costa Rican tropical forests to explore epiphytic trait divergence in a phylogenetic context. We examined leaf responses to water deficits in terrestrial, hemi-epiphytic and epiphytic ferns and related these findings to functional traits that regulate leaf water status. Epiphytic ferns had reduced xylem area (-63%), shorter stipe lengths (-56%), thicker laminae (+41%) and reduced stomatal density (-46%) compared to terrestrial ferns. Epiphytic ferns exhibited similar turgor loss points, higher osmotic potential at saturation and lower tissue capacitance after turgor loss than terrestrial ferns. Overall, hemi-epiphytic ferns exhibited traits that share characteristics of both terrestrial and epiphytic species. Our findings clearly demonstrate the prevalence of water conservatism in both epiphytic and hemi-epiphytic ferns, via selection for anatomical and structural traits that avoid leaf water stress. Even with likely evolutionarily constrained physiological function, adaptations for drought avoidance have allowed epiphytic ferns to successfully endure the stresses of the canopy habitat.