Leaf Water Potential Values Research Articles

Farklı Sulama Seviyeleri Altında Yetiştirilen İkinci Ürün Silajlık Mısır ve Sorgum Bitkilerinin Yaprak Su Potansiyellerinin Karşılaştırılması

Bu çalışma, 2018 ve 2019 yıllarında Kahramanmaraş İli Doğu Akdeniz Geçit Kuşağı Araştırma Enstitüsü Müdürlüğüne ait deneme alanlarında yürütülmüştür. Deneme ikinci ürün olarak yetiştirilen silajlık mısır ve sorgum bitkisinin yaprak su potansiyeli değerini belirlemek ve birbirleriyle karşılaştırmak amacıyla yapılmıştır. Denemede bitkilere 5 farklı sulama konusu (%100, %80, %60, %40 ve %20) uygulanmıştır. Tesadüf bloklarında faktöriyel deneme desenine göre düzenlenen konular üç tekerrürlü olarak uygulanmıştır. Çalışmanın sonuçlarına göre her iki bitkide de yaprak su potansiyeli değerleri %100 sulamanın yapıldığı konudan %20 sulamanın yapıldığı konuya doğru artış göstermiştir. Sulama öncesi ve sonrası değerler iki yıl birlikte değerlendirildiğinde mısır bitkisi %100 sulanan konuda -13.27 ile -21.76 bar, %80 sulanan konuda -14.07 ile -20.15 bar, %60 sulanan konuda -13.53 ile -19.67 bar, %40 sulanan konuda12.76 ile 21.76 bar, %20 sulanan konuda -13.30 ile -21.14 bar aralığında değişmiştir. Sorgum bitkisinde ise %100 sulanan konuda -14.24 ile -19.43 bar, %80 sulanan konuda -13.64 ile -20.19 bar, %60 sulanan konuda -14.73 ile -22.23 bar, %40 sulanan konuda -15.31 ile 21.73 bar, %20 sulanan konuda -14.06 ile -22.32 bar aralığında değişmiştir. Yaprak su potansiyeli su kısıntısının artmasıyla negatif yönde artış göstermiştir. Sulamadan sonraki değerler sulamadan önceki değerlerden düşük çıkmıştır. Silajlık sorgum bitkisinden mısır bitkisine göre daha düşük değerler elde edilmiştir.

Response of some physiological components of cotton to surface and subsurface drip irrigation using different irrigation water levels

This study was carried out to determine the leaf water potential (LWP), stomatal conductance (SC) and leaf area index (LAI) of cotton crop using subsurface drip irrigation (SSDI) and surface drip irrigation (SDI) and different irrigation water levels based on the FAO-56 Penman-Monteith (PM) during the 2016 and 2017 growing seasons. The critical LWPs in vegetative period, flowering stage and boll formation stage in SDI for irigation time were -24, -23 and -24 bar, respectively. Considering the same putting in order for the crop development stages in SSDI-40 cm, those were -23, -23 and -24 bar, respectively. The values of LWP in SSDI-30 cm were the same levels in SSD-40 cm. LWP in the boll formation stage were, in general, lower (bigger in minus numerical number) compared to the first two development stages of the crop. The critical SCs in vegetative period, flowering stage and boll formation stage in SDI were 312.8, 201.8 and 198.9 mmol m-2 s-1, respectively. The values of SC in the same putting in order for the crop development stages in SSDI-30 cm and SSDI-40 cm were 368.8, 182.6 and 221.8 mmol m-2 s-1; and 371.7, 185.9 and 186.8 mmol m-2 s-1, respectively. SC decreased from the vegetative period through generative period of the crop. The SCs increased together with increasing amount of irrigation water and it decreased with increasing water stress conditions. The LAIs were 2.99, 3.11 and 3.45 in SDI, SSDI-30 cm and SSDI-40 cm, respectively. The values of LAI increased from the surface drip irrigation and lower irrigation water level applied through subsurface drip irrigation and highest level of amount of irrigation water. Although some plant physiological indicators such as LWP and SC might be used for irrigation scheduling and irrigation time, these indicators are highly affected by soil water status, temperature, light, air humidity and calibration of the devices used.

Do invasive jumping worms impact sugar maple (Acer saccharum) water-use dynamics in a Central Hardwoods forest?

Although non-native earthworms are known to drastically change forest soils and understory plant communities, comparatively little is known about how the introduction of different earthworm groups may alter perennial plant functioning (i.e., physiological, morphological, and/or anatomical traits), or how these dynamics may vary between different earthworm groups. Our objective was to assess whether a recent replacement of European earthworms by Amynthas spp. (i.e., Asian “jumping worms”) in a Central Hardwoods forest of the Upper Midwest impacts patterns of water use in dominant overstory Acer saccharum Marshall (sugar maple). We found that (1) soil water content was often greater in Amynthas sites, (2) compared to those growing in sites with only European earthworms, A. saccharum growing with Amynthas had higher midday leaf water potential values (a measure of greater plant water status) early in 2017 but lower midday leaf water potential by the end of 2018, and (3) A. saccharum from Amynthas sites had fewer, but wider xylem conduits than trees from European sites, but this trend was not significant and was not associated with differences in stem hydraulic functioning between the two groups. Overall, these results suggest that Amynthas invasions may not impact the overstory of A. saccharum—dominated forests within the Upper Midwest, at least early during invasions of forests colonized by existing earthworms or during growing seasons with above-average precipitation. Future work should investigate the impacts of different earthworm groups on tree water and nutrient relations over longer periods of colonization and in different tree age classes.

Evaluation of crop water stress index and leaf water potential for differentially irrigated quinoa with surface and subsurface drip systems

A 2-year field experiment was conducted with the objectives to evaluate the physiological and yield response of quinoa cv Titicaca to various deficit irrigation strategies applied with surface drip (SD) and subsurface drip systems (SSD) under the Mediterranean climatic conditions in 2016 and 2017. The treatments consisted of regulated deficit irrigation (RDI), partial root-zone drying (PRD50), conventional deficit irrigations (DI50, DI75) and full irrigation (FI) under SD and SSD. A rainfed treatment was also included. The experimental design was split plots with four replications. DI75 and DI50 received 75 and 50% of FI, respectively. PRD50 plots received 50% of FI, but from alternative laterals in each application. RDI received 50% of FI during vegetative stage until flowering, then received 100% of water requirement. The results indicated that RDI resulted in water saving of 23 and 21% for surface drip (SD) and SSD systems, respectively, and RDI produced statistically similar yield to FI treatment in both experimental years. DI75 treatment resulted in water savings of 16% for both drip methods in the first year and 10 and 25% for SD and SSD systems, respectively, in the second year. Thus, RDI and DI75 treatments appear to be good alternative to FI for sustainable quinoa production in the Mediterranean environmental conditions. Greater leaf water potential (LWP) and smaller crop water stress index (CWSI) values were measured in FI plots under both drip systems than deficit irrigation treatment plots. Significant second-order polynomial relations were determined between CWSI and LWP for the drip systems. Leaf area index (LAI), LWP decreased and CWSI increased as the drought increased. CWSI correlated significantly (P < 0.01) and negatively with grain yield, dry matter yield, LAI, and mean soil water content indicating that grain yield of quinoa declined with increasing CWSI values. All these relations are best described by significant second-order polynomial equations. The results revealed that quinoa should be irrigated at LWP values between − 1.35 and − 1.60 MPa, and average CWSI value of approximately 0.35 for high yields.

Functional traits indicate faster resource acquisition for alien herbs than native shrubs in an urban Mediterranean shrubland

In urban Mediterranean ecosystems, invasive alien plants should have characteristics that enable faster resource acquisition and utilization than native species. We tested this hypothesis by comparing stem and leaf functional traits from five abundant native woody shrubs and five of the most abundant alien species within an urban coastal scrub community in Ensenada, Baja California, Mexico. Twelve anatomical and ecophysiological traits were studied: light-saturated CO2 assimilation rate, stomatal conductance, stem and leaf water potentials during transpiration, % stem allocation to bark, xylem and pith, stem xylem vessel diameter and density, leaf size, and % allocation to spongy and palisade mesophyll. Alien species varied more in these traits, and their trait combinations reflected less investment in long-lived tissues; they had higher CO2 assimilation and stomatal conductance rates, higher values of leaf and stem water potential, and higher allocation to pith, larger stem xylem vessels, and larger leaf areas. In contrast, native woody shrub species were relatively convergent in leaf and stem traits reflecting more conservative resource use. Within disturbed urban environments, alien species may outcompete the native stress-tolerant species through rapid resource acquisition, enhanced by a broader set of functional trait combinations across species.

Foliar Glycine Betaine or Hydrogen Peroxide Sprays Ameliorate Waterlogging Stress in Cape Gooseberry.

Exogenous glycine betaine (GB) or hydrogen peroxide (H2O2) application has not been explored to mitigate waterlogging stress in Andean fruit trees. The objective of this study was to evaluate foliar GB or H2O2 application on the physiological behavior of Cape gooseberry plants under waterlogging. Two separate experiments were carried out. In the first trial, the treatment groups were: (1) plants without waterlogging and with no foliar applications, (2) plants with waterlogging and without foliar applications, and (3) waterlogged plants with 25, 50, or 100 mM of H2O2 or GB, respectively. The treatments in the second trial were: (1) plants without waterlogging and with no foliar applications, (2) plants with waterlogging and without foliar applications, and (3) waterlogged plants with 100 mM of H2O2 or GB, respectively. In the first experiment, plants with waterlogging and with exogenous GB or H2O2 applications at a dose of 100 mM showed higher leaf water potential (−0.5 Mpa), dry weight (1.0 g), and stomatal conductance (95 mmol·m−2·s−1) values. In the second experiment, exogenously supplied GB or H2O2 also increased the relative growth rate, and leaf photosynthesis mitigating waterlogging stress. These results show that short-term GB or H2O2 supply can be a tool in managing waterlogging in Cape gooseberry.

Image-Based Assessment of Drought Response in Grapevines.

Many plants can modify their leaf profile rapidly in response to environmental stress. Image-based data are increasingly used to retrieve reliable information on plant water status in a non-contact manner that has the potential to be scaled to high-throughput and repeated through time. This paper examined the variation of leaf angle as measured by both 3D images and goniometer in progressively drought stressed grapevine. Grapevines, grown in pots, were subjected to a 21-day period of drought stress receiving 100% (CTRL), 60% (IRR60%) and 30% (IRR30%) of maximum soil available water capacity. Leaf angle was (i) measured manually (goniometer) and (ii) computed by a 3D reconstruction method (multi-view stereo and structure from motion). Stomatal conductance, leaf water potential, fluorescence (Fv/Fm), leaf area and 2D RGB data were simultaneously collected during drought imposition. Throughout the experiment, values of leaf water potential ranged from −0.4 (CTRL) to −1.1 MPa (IRR30%) and it linearly influenced the leaf angle when measured manually (R2 = 0.86) and with 3D image (R2 = 0.73). Drought was negatively related to stomatal conductance and leaf area growth particularly in IRR30% while photosynthetic parameters (i.e., Fv/Fm) were not impaired by water restriction. A model for leaf area estimation based on the number of pixels of 2D RGB images developed at a different phenotyping robotized platform in a closely related experiment was successfully employed (R2 = 0.78). At the end of the experiment, top view 2D RGB images showed a ∼50% reduction of greener fraction (GGF) in CTRL and IRR60% vines compared to initial values, while GGF in IRR30% increased by approximately 20%.

Bradyrhizobium Inoculation Plus Foliar Application of Salicylic Acid Mitigates Water Deficit Effects on Cowpea

To evaluate the interaction between foliar application of salicylic acid and Bradyrhizobium inoculation on the morphophysiology of cowpea under water stress conditions, four genotypes (BRS Rouxinol, BRS Marataoa, BRS Arace and BR 17 Gurgueia) were subjected to five combinations of water availability: 100% replacement of crop evapotranspiration (control); 50% replacement of crop evapotranspiration (water stress); water stress + salicylic acid; water stress + Bradyrhizobium inoculation; and water stress + salicylic acid + Bradyrhizobium inoculation. The experiment was set up in a 4 × 5 factorial randomized block design, with four replicates and four plants per plot. Water stress negatively affected the leaf water potential, growth, proline contents and antioxidant activity of the cowpea genotypes, and BRS Marataoa was the most sensitive. Under water stress conditions, Bradyrhizobium inoculation was efficient for BRS Rouxinol, but was only efficient for BRS Marataoa, BRS Arace and BR 17 Gurgueia when associated with foliar application of salicylic acid, maintaining their values of leaf water potential, growth, proline content and activities of superoxide dismutase, ascorbate peroxidase, and catalase similar to those of the control treatment.

Evaluation of the efficiency of irrigation methods on the growth and survival of tree seedlings in an arid climate

Scarce and scattered precipitation in arid regions is detrimental for newly planted seedlings. It is essential to provide required water storage for seedlings in restoration projects in the first year of their establishment. The subsurface irrigation can be much more effective than the surface irrigation because of the regulation of water availability and reduction in water evaporation. We studied the effect of surface and subsurface irrigation methods on the growth and survival of four common tree species including heaven tree (Ailanthus altissima (Mill.) Swingle), China berry (Melia azedarach L.), white mulberry (Morus alba L.), and black locust (Robinia pseudoacacia L.) by installing underground clay reservoirs with different permeabilities in Isfahan City, Iran. Different amounts of animal manure and wheat straw were mixed with clay fraction and cooked in a pottery kiln at 900°C to produce reservoirs with different permeabilities. The experimental treatments consisting of irrigation and tree species were considered with a factorial arrangement in a completely randomized design with three replications in 2016 and 2017. Leaf water potential of seedlings, which is indirectly related to drought resistance, was measured by a portable pressure chamber. The results showed that saplings height, basal diameter, number of leaves, chlorophyll content and stomatal conductance were significantly (P<0.05) higher in the subsurface irrigation with low permeability than in the surface irrigation, but the number of branches of the studied species were not significantly (P>0.05) affected by the irrigation methods and different permeabilities of clay reservoirs. The clay reservoirs with low and medium permeabilities constantly provide better conditions for plant growth, and water with lower pressure and longer time intervals to the plant roots as compared with the reservoirs with high permeability. Analysis of variance of the data showed that year and interaction between year and permeability of reservoir had significant effects (P<0.05) on all growth parameters, except for the chlorophyll content. In addition, the highest percentage of survival was 100% associated with the subsurface irrigation and the control treatment had the lowest survival percentages of 60%, 70%, 80% and 100% for M. alba, M. azedarach, A. altissima and R. pseudoacacia, respectively. Finally, the values of leaf water potential showed that R. pseudoacacia was the most drought resistant species.

Plant-available water, stem diameter variations, chlorophyll fluorescence, and ion content in Pistacia lentiscus under salinity stress

The aim of this study was to investigate the physiological and hydric adaptability of Pistacia lentiscus (lentisco) to saline irrigation conditions. Plants of lentisco were subjected to four salinity treatments in the irrigation water (0, 50, 100 y 150 mM NaCl) during three months in a growth chamber in order to identify possible tolerance mechanisms to salinity stress. The results showed a reduction of aerial growth parameters, mainly in the 150 mM of NaCl treatment. The root biomass did not change; however, the root hydraulic conductivity was modif ied. This behavior was related with decreases in leaf water potential values both at morning and midday. With the increase of salinity in the irrigation water, the radial growth of stem of the plants was proportionally decreased, and Cl- and Na+ content at minimum and maximum illumination in leaves and roots increased. Stomatal conductance decreased in the plants with higher salinity level, although chlorophyll content and fluorescence were not affected by the salinity treatments. Although the growth rates were statistically affected in all the treatments, the plants were able to resist the salt stress through changes in the leaf structures, related to a reduction of water losses via transpiration.

Managing high quality timber plantations as silvopastoral systems: tree growth, soil water dynamics and nitrate leaching risk

The management of high-quality timber plantations prioritizes obtaining high productions with short rotation cycles, which results in high economic and environmental costs, similar to intensive agricultural systems. The suppression of the herbaceous understorey by ploughing, and the use of fertilizers to boost tree growth potentially pose high environmental risks. Managing these plantations as silvopastoral systems (e.g. by introducing livestock and sowing legume-rich pastures) could reduce environmental risks. However, this management shift can only be effective if it is accompanied by an increased complementarity in the use of soil resources to maintain production. We evaluated rooting systems, tree water status and growth, pasture production, soil moisture and nitrate content in the soil solution in a 13-year-old hybrid walnut (Juglans major × regia) plantation under alternative management schemes. The management aimed at reducing herbaceous understorey cover (grazing, ploughing and mowing) and fertilizer usage (no fertilization, inorganic fertilization and legume sowing). Grazed and mowed plots had higher root surface density than ploughed plots. Ploughed plots also showed lower values of soil water (in summer) and tree leaf water potential than grazed and mowed plots. Tree growth and nitrate content in the soil solution was higher in ploughed than grazed or mowed plots. Fertilized and sown plots had higher understorey biomass and lower soil water (in summer) than unfertilized plots. Tree growth was higher in fertilized than unfertilized plots, with intermediate values in sown plots. Managing high-quality timber plantations under silvopastoral schemes with improved legume-rich forages might be a feasible way to reduce the high ecological maintenance costs of these plantations, without compromising their productivity.

The hydraulic redistribution on cashew (Anacardium occidentale L.) at nursery stage

Cashew plants can distribute soil water vertically from waterier subsoil to drier topsoil, called as hydraulic lift (HL). There is no report on its ability to distribute soil water laterally or hydraulic redistribution (HR). This study was conducted at ISMCRI greenhouse from March-October 2018. Cashew varieties B-02 were planted in pot, then set in three treatments : (1) two parts of the roots in water sufficient (WW), (2) one part of the roots in drought stress and one part in water sufficient (WD), and (3) both parts of the roots put in drought stress conditions (DD). The study was arranged in a complete randomized design, nine replications. The results showed proportion of root biomass in drought stress to total root biomass was relatively same between WD and DD (0.4). The soil moisture value in WD plants were significantly higher than that of DD (1-3%) for 7 days period. Water status in plant tissue presented by the leaf water potential, showed the same tendency. The leaf water potential value of WD plants was between DD and WW. These indicated that cashew plants possessed HR ability, being able to transfer soil water laterally and maintained relatively high soil moisture in the roots.

Early water stress effects on pollen viability, berry set and embryo development in cv. 'Syrah' (Vitis vinifera L.)

Early water deficit at bloom results in poor berry set and/or a grape yield reduction. The purpose of this work was to determine the effects of early water stress in a berry’s development. The experiment was carried out in a SupAgro ECOTRON System in Montpellier, France. Seven year- old ‘Syrah’ vines were used. The pot’s surface was protected from rainfall, and the growing medium was perlite+coarse sand with controlled drainage. The treatments were WS&lt;sub&gt;0&lt;/sub&gt; (control): 4 l/day, WS&lt;sub&gt;1&lt;/sub&gt;: 3 l/day, WS&lt;sub&gt;2&lt;/sub&gt;: 2 l/day, and WS&lt;sub&gt;3&lt;/sub&gt;: 1 l/day. The water deficit was carried out from the 17&lt;sup&gt;th&lt;/sup&gt; to the 27&lt;sup&gt;th&lt;/sup&gt; Eichhorn-Lorenz (E-L) stages. In order to emphasise details of the embryo development, a paraffin section method and technique was used. With the early water stress, there was no effect on the pollen viability and pollen germination ratios. The berry set ratio was reduced and the berry development were affected negatively by the early water stress. Between the 19&lt;sup&gt;th&lt;/sup&gt; and the 27&lt;sup&gt;th&lt;/sup&gt; E-L stages, an early water stress in ‘Syrah’ was noted, with decreases in the pre-dawn leaf water potential values below –0.8 MPa. The water deficit affected the berry growth and the development negatively.

Yüzeyaltı Damla Sulama Yöntemiyle Sulanan Yalova İncisi Sofralık Üzüm Çeşidinde Yaprak Su Potansiyeline Göre Sulama Programının Oluşturulması

This research was carried out in the Eastern Mediterranean Region of Turkey where to determine the effects of various irrigation strategies applied with subsurface drip systems on Yalova Incisi table grape variety and yield and water use efficiency along with optimal irrigation program during 2016, in the experimental fields of Alata Horticultural Research Station, Tarsus Soil and Water Resources Topcu Unit. In the study six irrigation levels (Full irrigation, TS; deficit irrigation, KS75; deficit irrigation, KS50; Partial Root-Zone Drying PRD75% , Partial Root-Zone Drying PRD50% of full irrigation treatments and Rainfed, RF) were tested. Soil water deficit in the rootzone depth was replenished to field capacity in irrigations. The experimental was carried out in randomized block design with three replications. The effect of the irrigation levels on the yield were found statistically significant. Full irrigation treatment under the produced the highest yield (30.9 t ha-1), the lowest yield was obtained in rainfed treatment plots (11.7 t ha-1). Leaf water potantial were measured throughout the growing season with a pressure chamber. The YSP values decreased with increasing water stress. Highest yields of Yalova Incisi variety can be obtained when irrigated at leaf water potential value Ψ =0.92 MPa.

Foliar water-uptake strategies are related to leaf water status and gas exchange in plants from a ferruginous rupestrian field.

Fog is a frequent event in Brazilian rupestrian field and plays an important role in the physiology of several plant species. Foliar water uptake (FWU) of fog may be fast or slow depending on the species. However, fog water may negatively affect CO2 assimilation. Thus, the interference in the water and carbon balance as a result of different strategies of FWU was evaluated to verify whether fog may mitigate possible water deficit in leaves. Four plant species with different FWU strategies were studied in a ferruginous rupestrian field with frequent fog. Gas exchange and water potential were measured before dawn and at midday during the dry and rainy seasons, separating foggy from non-foggy days during the dry season. The FWU speed negatively influences CO2 assimilation in the dry season, possibly because of its negative relationship with stomatal conductance, since reduced stomatal aperture impairs carbon entrance. Fog presence increased leaf water potential both in early morning and midday during the dry season. However, during the rainy season, the values of leaf water potential were lower at midday, than during the dry season with fog at midday, which favors leaf gas exchanges. FWU interferes negatively, but briefly with CO2 assimilation. Nevertheless, FWU prevents water loss through transpiration and increases the water status of plants in the dry season. That is, FWU results in a compensation between CO2 assimilation and foliar hydration, which, in fact, is beneficial to the plants of this ecosystem.

EFFECT OF IRRIGATION REGIMES, NITROGEN, AND MULCHING TREATMENTS ON WATER PRODUCTIVITY OF TOMATO UNDER DRIP IRRIGATION SYSTEM

A field experiment was conducted at El-Intelaq area, West Nubaria region, Behaira Governorate (31o 02' N, 30o 28' E, and 6.7 m above mean sea level), Egypt during the 2012 and 2013 summer growing seasons to study the effect of three irrigation treatments (i.e., I1=75%, I2 = 100%, and I3 = 125% of reference ETo, which was estimated from class ‘A’ pan evaporation and Kpan=0.75, two nitrogen fertilizer levels (i.e., N1= 75%, and N2=100% of recommended nitrogen rate), and two crop residuals mulching treatments (i.e., M0 = without mulch, and M = with mulch) on tomato yield, amounts of applied irrigation water, water consumption, applied water productivity (AWP), leaf water potential, and to develop a local tomato crop coefficient (Kc) and yield response factor (Ky) under the experimental conditions. Results indicated that, the tested variables had significant effect on tomato yield in the two growing seasons. The highest tomato fruit yields of 80.57 and 64.42 ton/ha were obtained as a result of the interaction of I3 (125%ETo) and N2 treatment in the two growing seasons, respectively. Total depths of applied irrigation water and water consumption of 816.2 and 838.0mm and 573 and 574mm were recorded in the 1st and 2nd growing seasons, respectively, for the I3 irrigation treatment. In both seasons, the highest AWPs values were 9.73 and 9.42 kg/m3 due to the combined effect of irrigation treatment I1 (75% Epan) and N2 (100% of recommended nitrogen fertilizer). Leaf water potential values were lower with the high applied water treatment than with the stressed irrigation treatment. Average crop coefficient values were 0.51 at initial growth stage during June and reached its maximum value of 0.98 during August, and then decreased to 0.71 during October. The local seasonal average tomato crop coefficient (KC=ETc/ETo) and yield response factor (Ky) values under the experimental conditions were 0.74 and 0.82, respectively. It was concluded that, under similar field conditions, applying a depth of water equal to 125% of ETo and 100% of the recommended nitrogen fertilizer, and adding plant residue mulch is recommended for maximum tomato yield in the studied sandy soils under drip irrigation systems.

The intensity of and recovery from photoinhibition under drought in a thermotolerant common bean compared to drought tolerant genotypes

The chlorophyll a fluorescence parameters of four Phaseolus vulgaris L. genotypes were evaluated under drought in two greenhouse experiments. Under severe water stress, the thermotolerant genotype 'Diplomata' maintained significantly higher values of predawn leaf water potential (Ψw), maximum Fv/Fm and effective (ΦPSII) quantum yield of photosystem II , and non-photochemical quenching than 'Ouro Negro', in the first experiment, and 'A 285' and 'A 222', in the second one. Among these parameters, Fv/Fm showed more differences that discriminated between the genotype responses even when measured at night. Next, a difference between Fv/Fm after sundown and Fv/Fm at dawn on the same day (day ∆Fv/Fm), i.e., the intensity of photoinhibition, and a difference between Fv/Fm at dawn and Fv/Fm after sundown on the day before (night ∆Fv/Fm), i.e. the photoinhibition recovery, were evaluated. Day ∆Fv/Fm and night ∆Fv/Fm were significantly higher for 'Diplomata' under severe water stress in both experiments. In addition, 'Ouro Negro' in the first experiment and all the genotypes in the second showed negative values of night ∆Fv/Fm on the last day of drought when their Ψw were also minimal indicating no recovery from photoinhibition and the need for rehydration. At maturation, stressed plants of 'Diplomata' showed a significantly higher yield than 'Ouro Negro' in the first experiment and the same as 'A 285' in the second. Therefore, the thermotolerant genotype 'Diplomata' also showed drought tolerance, and the use of day ∆Fv/Fm and night ∆Fv/Fm fluorescence analysis was able to discriminate between the tolerances of these genotypes and to indicate the need for rehydration.

Photosynthetic Characterization and Response to Drought and Temperature in Wild Asparagus (Asparagus acutifolius L.)

The wild asparagus species Asparagus acutifolius L. is widespread in Mediterranean and subtropical environments, where its spears are consumed regularly. The species is known to have ecophysiologic plasticity, however there is no literature on this subject. This work aimed at assessing the photosynthetic characteristics of this wild species of asparagus, grown under full light (FL) and partial (i.e., about 40%) light (PL) conditions, and evaluating its ecophysiologic response to drought and temperature stress. The photosynthetic response to light of spears and of new cladodes (NC; current year) and old cladodes (OC; previous year) was measured using an infrared gas analyzer coupled with a climatized cuvette chamber. Cladodes net photosynthesis at high irradiance was also measured at varying air temperatures and decreasing soil water availability. Results indicate that developing spears were photosynthetically active with no difference between FL and PL treatments. Photosynthetic rates did not differ between NCs and OCs and were greater for FL cladodes, except at low irradiance. Well-watered plants were photosynthetically active from 0 to 45 °C, with a maximum photosynthetic rate of up to 9 µmol·m–2·s–1 at 30 °C and a decrease of about 60% at 45 °C. The species also demonstrated high tolerance to drought, with positive net photosynthesis even at predawn leaf water potential values of –2.4 MPa. Showing great ecophysiologic plasticity, this wild asparagus could be an interesting species in areas were conventional crop species are not profitable economically, or as an intercrop in agroforestry systems.

Approach to Yield Response of Young Almond Trees to Deficit Irrigation and Biostimulant Applications

Water is the most limiting resource in many semi-arid areas of Mediterranean countries. Among the strategies to improve water productivity, the implementation of deficit irrigation (DI) strategies and the introduction of drought-tolerant crops in irrigated areas (such as almond) are being widely studied. Recently, the use of biostimulants to enhance crop tolerance to drought under water-scarcity scenarios is increasing. This work examines the response of three almond cultivars (‘Guara’, ‘Marta’, and ‘Lauranne’) in terms of yield and associated physiological responses in the main phenological stages to biostimulants (HYT® A and HYT® B plus) applied to young trees subjected to different irrigation levels: (i) a full irrigation treatment (FI), irrigated at 100% of crop evapotranspiration (ETC); and (ii) sustained-deficit irrigation (SDI75), irrigated at 75% of ETC. Significantly higher yields were obtained with HYT applications in 2 of 3 cultivars; these differences were most evident in the SDI75 treatment. In particular, ‘Guara’ registered the most significant improvements in nut yield when the HYT product was applied (15–20% higher). With regard to crop physiological responses, higher values of leaf water potential and stomatal conductance were noted with the HYT application in some cultivars and phenological stages. These results indicated that the use of biostimulants can be a feasible strategy for almond cultivation, especially when SDI is used.

Investigation of physiological changes in the affected Quercus brantii stand by oak charcoal disease

The purpose of this work was to monitor the effects of the environmental factors include temperature, precipitation and sun radiation on some physiological aspects of Q. brantii trees in the forest stand involved with the oak charcoal disease during a growing season. We designed a systematic random sampling and all trees were examined for disease status. Our result showed that 70.96% of the trees with different intensities are affected by the charcoal disease. Accordingly, values of predawn leaf water potential (PWP), midday leaf water potential (MWP) and chlorophyll variables showed significant difference in classes of oak charcoal disease. Linear regression analysis showed that the values of PWP, MWP and chlorophyll are changing at the high temperature. Mean of canker length are 20.5 cm and 51.7 cm in class 2 and 3 respectively and there is a great relation between PWP value and canker length (r&lt;sup&gt;2&lt;/sup&gt; = 0.914). Canker length also has a linear relation with MWP values (r&lt;sup&gt;2&lt;/sup&gt; = 0.627). Drought stress affected the physiological functions of oak trees and considerably reduced their defense potential against pathogen agents.