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Rice (Oryza sativa L.), an important food crop, necessitates more water to complete its life cycle than other crops. Therefore, there is a serious risk to rice output due to water-related stress. Drought stress results in morphological changes, including the inhibition of seed germination, reduced seeding growth, leaf area index, flag leaf area, increased leaf rolling, as well as the decrement of yield traits, such as plant height, plant biomass, number of tillers, and 1000-grain yield. Stress also causes the formation of reactive oxygen species (ROS) such as O2−, H2O2, and OH−, which promote oxidative stress in plants and cause oxidative damage. The process of oxidative degradation owing to water stress produces cell damage and a reduction in nutrient intake, photosynthetic rate, leaf area, RWC, WUE, and stomatal closure, which may be responsible for the decrement of the transpiration rate and plant dry matter under decreasing soil moisture. Plants have the ability to produce antioxidant species that can either be enzymatic (SOD, POD, CAT, GPX, APX) or non-enzymatic (AsA, GSH) in nature to overcome oxidative stress. During drought, several biochemical osmoprotectants, like proline, polyamines, and sugars, can be accumulated, which can enhance drought tolerance in rice. To meet the demands of an ever-growing population with diminishing water resources, it is necessary to have crop varieties that are highly adapted to dry environments, and it may also involve adopting some mitigation strategies. This study aims to assess the varying morphological, physiological, and biochemical responses of the rice plant to drought, and the various methods for alleviating drought stress. [ABSTRACT FROM AUTHOR]

Objective: This research was carried out in order to investigate the effect of irrigation regimes on morphological traits of root and shoot of safflower genotypes. Methods: A field experiment has been conducted via polyvinyl chloride (PVC) pipes at research field of Seed and Plant Improvement Institute in Karaj, during 2019-2020. A factorial experiment has been laid out in a randomized complete block design with three replications. This study deals with six genotypes of safflower (Varamin landrace, Hamand landrace, Kazakhstan genotype and Amir, Goldasht and Pernian cultivars) in two irrigation regimes, including full irrigation (control) and drought stress (Irrigation after depletion of 40% and 80% of soil available moisture respectively) treatments. Results: The results showed that under drought stress conditions, root length and root diameter have increased by 28.6% and 13.6%, respectively and root dry weight, leaf relative water content (RWC), number of bolls, number of seeds per plant and seed yield per plot and was decreased by 23.6%, 15.2%, 25.4%, 63.3%, and 74.9%, respectively. Under full irrigation conditions, Amir with suitable root system (root dry weight 7.7 g and root length 71 cm) and maximum number of seeds had the highest seed yield (5.03 g per plot). In addition, under drought stress conditions, Amir cultivar had early flowering, maximum root dry weight and length, highest activity of catalase and peroxidase enzymes, and the highest seed yield per plot (1.67 g). Conclusion: Generally, Amir cultivar had more seed yield due to having a suitable root system and superior agronomic characteristics and was selected as the superior genotype. [ABSTRACT FROM AUTHOR]

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.

Pistacia atlantica Desf. (Beneh) is an important woody species that has been facing significant challenges to its natural regeneration and reforestation in Iran. This study investigates the interaction of soil moisture and shade on growth, chemical contents, and morphological and physiological characteristics of Beneh saplings. One-year-old Beneh saplings were treated with varying amounts of soil moisture (20, 50, and 100% of field capacity) and shade (0, 30, and 50% of full sunlight) in a split-plot experiment of a randomized complete block design in semiarid conditions of the Alborz Research Station of the Research Institute of Forests and Rangelands (RIFR) in Iran. The results indicate that soil moisture significantly affects the water content of the leaf, total chlorophyll, proline content, activity of catalase enzyme, leaf dry biomass, leaflet area, and dry stem biomass in the leaf. Shade significantly affected total chlorophyll, catalase enzyme activity, specific leaflet area, relative water content of the leaf, proline content, dry root biomass, and leaflet area. The interaction of shade and soil moisture significantly affected seedling height, catalase enzyme activity, specific leaflet area, and nitrogen and potassium content of the leaf. Shade moderates the stress of drought on Beneh saplings, but shading of Beneh saplings is not recommended in conditions where there is no concern about soil moisture. These conclusions can be used to improve the production of Beneh saplings in nurseries. [ABSTRACT FROM AUTHOR]

Drought stress during wheat (Triticum aestivum L.) grain filling can affect the grain yield and its quality; effects that in some regions can be increased by the event La Niña, the cold phase of the climatic phenomenon El Niño Southern Oscillation. The aim was to evaluate if the evolution of relative water content (RWC) and stomatal conductance (gs) can be related to grain yield and its quality. Four spring wheat cultivars grown in the southern cone of South America were subjected to two levels of irrigation applied after anthesis, a well-watered treatment (Control), and another with 50 % of the Control (Stress). RWC and gs were determined weekly during the stress period and agronomic traits at harvest. With a mean grain yield decrease of 14.8 % (P

Drought drastically affects plant growth and development, and thus reduces crop productivity. Drought stress tolerance in wheat is a prime factor for stabilization of crop performance in the drought-prone environments. It is not a simple response but mostly conditioned by many components' responses, which interacts and may differ for crops, concerning types, intensity and duration of water deficiency. Moreover, most agronomical characters inherit differently in normal and stress conditions and are known to be affected by environmental factors. Therefore, selection based on the phenotype is difficult for such traits. Wheat (Triticum Aestivum L.) occupies 220 million hectares i.e., 17% of the total cultivated land in the world and supports nearly 35% of the world's population. The main objective of this study was to observe the response of 40 wheat cultivars to drought tolerance by evaluation through polyethylene glycol (PEG) mediated moisture stress under laboratory conditions. Seedling traits studied in two different concentrations of PEG (20% & 30%). The result showed that with increasing PEG concentration the seedling traits decreased and at 30% of PEG, no germination observed. Physiological parameter such as relative water content (RWC) was very responsive to drought stress and has been shown associated well with drought tolerance. Under osmotic stress, maximum relative water contents observed in Inqilab-91, Chakwal-50 and LLR-17. Furthermore, under stress condition amount of proline content increased significantly in all wheat cultivars in comparison to control. Based on root/shoot/coleoptile length, dry root/shoot weight and proline contents Chakwal-97, Inqilab-91, Pak-81, Faisalabad-08 and Fareed-06 found drought-tolerant cultivars. [ABSTRACT FROM AUTHOR]

Sugarcane (Saccharum sp.) is one of the most important sugar producing crops, and plays a key role in ethanol production in most tropical and subtropical countries. Selection of sugarcane varieties has traditionally been based on yield and agronomic traits; however, the use of physiological traits in sugarcane selection may increase selection efficiency. The objective of this study was to investigate the effects of physiological responses on yield and yield components in sugarcane under rainfed conditions. Nineteen elite sugarcane clones were evaluated in a randomized complete block design with three replications, from January, 2015 to January, 2016; at the Agronomy Research Station, Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand. The plots consisted of four rows, six meters in length, and spacing of 1.5 m x 0.5 m. Data were recorded for chlorophyll fluorescence, SPAD chlorophyll meter reading (SCMR), relative water content (RWC), stomatal conductance at 90 and 180 days after planting (DAP), stalk height, increased stalk height rate, number of tillers/stool, number of stalks/stool at 90, 180, and 270 days after planting (DAP); stalk diameter, stalk length, number of stalks/stool, single stalk weight, millable cane, cane yield, and total soluble solids at 12 months after planting (MAP). KK3 proved to be a superior clone for agronomic traits; such as cane yield, millable cane, stalk diameter, stalk length, total soluble solids; and was also associated with several physiological traits; such as high photosynthesis efficiency, SCMR, and stomatal conductance. Other comparative clones; such as KK07-037, MPT02-458, CSB07-79, K88-92, KKU99-01, and TBy28- 0941 had similarly high cane yields; whereas CSB07-219, MPT02-458, KKU99-02, KKU99-03, TP06-419, and UT13 had higher total soluble solids. [ABSTRACT FROM AUTHOR]

Highlights • Methodology for estimation of RWC in crops and a comprehensive comparative demonstration of various modeling techniques. • The order of performance with respect to R2 and RMSEP is as follows: PLSR-MLR > PLSR-ANN > SVR > RF > PLSR > ANN. • Models developed using PLSR selected wavebands yielded more satisfactory results. • Water Deficit Stress in Rice crops can be quantified using the modelling approach evaluated through this study. Abstract This study was conducted to understand the behaviour of ten rice genotypes for different water deficit stress levels. The spectroscopic hyperspectral reflectance data in the range of 350–2500 nm was recorded and relative water content (RWC) of plants was measured at different stress levels. The optimal wavebands were identified through spectral indices, multivariate techniques and neural network technique, and prediction models were developed. The new water sensitive spectral indices were developed and existing water band spectral indices were also evaluated with respect to RWC. These indices based models were efficient in predicting RWC with R2 values ranging from 0.73 to 0.94. The contour plotting using the ratio spectral indices (RSI) and normalized difference spectral indices (NDSI) was done in all possible combinations within 350–2500 nm and their correlations with RWC were quantified to identify the best index. Spectral reflectance data was also used to develop partial least squares regression (PLSR) followed by multiple linear regression (MLR) and Artificial Neural Networks (ANN), support vector machine regression (SVR) and random forest (RF) models to calculate plant RWC. Among these multivariate models, PLSR-MLR was found to be the best model for prediction of RWC with R2 as 0.98 and 0.97 for calibration and validation respectively and Root mean square error of prediction (RMSEP) as 5.06. The results indicate that PLSR is a robust technique for identification of water deficit stress in the crop. Although the PLSR is robust technique, if PLSR extracted optimum wavebands are fed into MLR, the results are found to be improved significantly. The ANN model was developed with all spectral reflectance bands. The 43 developed model didn't produce satisfactory results. Therefore, the model was developed 44 with PLSR selected optimum wavebands as independent x variables and PLSR-ANN model 45 was found better than the ANN model alone. The study successfully conducts a comparative 46 analysis among various modelling approaches to quantify water deficit stress. The methodology developed would help to identify water deficit stress more accurately by predicting RWC in the crops. [ABSTRACT FROM AUTHOR]

• The effects of summer pruning (elimination of suckers) on olive were evaluated. • In summer, it determined higher relative water content (RWC) and greater photosynthetic activity. • At harvest, it determined a higher fruit oil content on a dry-weight basis. • The extracted oil was less rich in phenolic compounds and was more herbaceous and fruitier, and less bitter and spicy. • Overall, the results indicate that summer pruning can have effects similar to irrigation. An investigation was carried out in 2017 in central Italy, in an adult olive orchard with trees of the cultivar Leccino, spaced 5 × 5 m, trained to a vase and pruned biennially. The aim was to evaluate the effects of summer pruning (i.e. eliminating suckers, in the central part of the canopy, in the non-pruning year), on the water status and physiology of the leaves, on the yield/tree, and on fruit characteristics and oil quality. Unpruned trees were used as the control. During the investigation (July-October), rainfall was low (less than 100 mm) and the orchard was not irrigated. During the summer, the leaves of summer-pruned trees had higher relative water content (RWC) and greater photosynthetic activity than those of control trees. Summer-pruned trees had similar yield, but higher oil content on a dry-weight basis. Oil qualitative parameters (free acidity, peroxide value and spectrophotometric absorbances in the ultra-violet) were similar, whereas the total content of phenolic compounds was higher in control trees. The oils from summer-pruned trees were more herbaceous and fruity, and less bitter and spicy than oils from control trees. The results show that in situations where there is considerable formation of suckers, such as in the case of biennial, triennial or plurennial pruning, summer pruning can contribute to improving tree water status and the physiological condition, favoring photosynthetic activity. This practice also has effects on fruit oil content and oil quality, producing more aromatic and less bitter and spicy oil. Overall, the results indicate that summer pruning can have effects similar to irrigation. [ABSTRACT FROM AUTHOR]

به‌منظور بررسی تأثیر تنش خشکی بر برخی ویژگی­ های فیزیولوژیک گیاه دارویی آویشن قره­ باغی (Thymus fedtschenko) آزمایشی در سال 1393 در گلخانه تحقیقاتی دانشگاه یزد اجرا شد. تیمارهای رطوبتی شامل 100، 75، 50 و 25 درصد ظرفیت زراعی بودند که بر اساس طرح بلوک­های کامل تصادفی با چهار تکرار اجرا شدند. نتایج نشان داد که تأثیر تنش خشکی بر محتوی کلروفیل a، کلروفیل b، کلروفیل کل، پرولین و گنجایش نسبی آب برگ در سطح احتمال یک درصد معنی­دار بود ولی بر میزان قند محلول اثر معنی­داری نداشت. افزایش تنش خشکی موجب افزایش محتوی پرولین و گنجایش نسبی آب برگ شد، به­ طوری­که کمترین مقدار این شاخص­ها در تیمار 100 درصد ظرفیت زراعی به دست آمد. بیشترین مقدار کلروفیل a، b و کلروفیل کل به ترتیب با 0/48، 167/ 0 و0/663 میلی­ گرم در گرم، مربوط به تیمار 25 درصد و کمترین مقدار این شاخص­ها مربوط به تیمار 100 درصد ظرفیت زراعی بود. درمجموع نتایج این تحقیق نشان داد که آویشن قره­باغی با به‌کارگیری برخی مکانیسم­های دفاعی از قبیل افزایش پرولین و محتوای کلروفیل قابلیت سازگاری با شرایط خشک را دارا می­باشد.

Although water and land pollution are very dangerous, air pollution has its own peculiarities due to its transboundary dispersion of pollutants over the entire world. In any well planned urban set up, industrial pollution takes a back seat and vehicular emissions take precedence as the major cause of urban air pollution. In the present study, Air pollution tolerance index was calculated for various plant species growing at two sites Nagal village at Sahastradhara Road and the Clock Tower (the experimental site) of Dehradun city, India. The leaf samples were collected from 7 commonly present tree species. The results showed significant effects of various air pollutants on the vegetation in terms of four biochemical parameters analysed. Four physiological and biochemical parameters, which are leaf relative water content, Ascorbic acid content, total leaf chlorophyll content and leaf extract pH were used to compute the air pollution tolerance index values. Statistically significant difference was observed between control and experimental group for Ascorbic acid, t(6)=-4.848,p=.003. Paired t test for air pollution tolerance index between the two groups showed a statistically significant difference, t (6) = -4.548, p=.004. On the basis of air pollution tolerance index values for above mentioned seven tree species, Eucalyptus globus exhibited the highest degree of tolerance at all the sites followed by Ficus religiosa > Mangifera indica > Polyalthia longifolia > Phyllanthus emblica > Citrus limon > Lantana camara.

به‌منظور بررسی ویژگی­های زراعی، فیزیولوژیک و کیفی کلزا تحت تنش آبیاری، آزمایشی در قالب طرح بلوک­های کامل تصادفی با سه تکرار در مزرعه پژوهشی دانشگاه آزاد اسلامی واحد شهرقدس در سال زراعی 90-1389 اجرا شد. در این آزمایش تیمار آبیاری در سه سطح شامل آبیاری مطلوب در طول دوره رشد بر اساس ٨٠ میلی­متر تبخیر از سطح تشتک تبخیر کلاس A به­ عنوان شاهد، قطع آبیاری از مرحله گل­دهی تا رسیدگی فیزیولوژیک، و قطع آبیاری از خورجین­ دهی تا مرحله رسیدگی فیزیولوژیک بود. نتایج حاصل نشان داد که اثر آبیاری بر ارتفاع بوته، قطر ساقه، تعداد شاخه­ فرعی، محتوای آب نسبی برگ، کمبود اشباع آب، میزان کلروفیل a و کارتنوئیدها، طول خورجین، تعداد خورجین در بوته، وزن هزار دانه، عملکرد دانه، درصد روغن، عملکرد روغن، شاخص برداشت و تلاش بازآوری معنی­ دار بود. قطع آبیاری از مراحل گل­دهی و خورجین­ دهی به بعد به­ ترتیب سبب کاهش 43/1 و 29/5 درصد محتوای نسبی آب برگ، 32/7 و 26/5 درصد میزان کلروفیل a و 49/6 و 31/8 درصد میزان کاروتنوئید در مقایسه با آبیاری مطلوب (شاهد) گردید. در این بررسی بیشترین عملکرد دانه در تیمار آبیاری مطلوب مشاهده شد و در شرایط قطع آبیاری از مراحل گل­دهی و خورجین­ دهی به بعد به­ ترتیب عملکرد دانه از 2577 کیلوگرم در هکتار در تیمار شاهد به 1483 و 1907 کیلوگرم در هکتار کاهش یافت. بین عملکرد دانه با اجزاء عملکرد به‌جز تعداد دانه در خورجین همبستگی مثبت و معنی­داری مشاهده شد و بیشترین همبستگی عملکرد دانه به ترتیب با وزن هزار دانه و تعداد خورجین در بوته بود. نتایج کلی این بررسی نشان داد که قطع آبیاری از مرحله گل­دهی تا رسیدگی فیزیولوژیک اثرات منفی شدیدتری بر ویژگی­ های فیزیولوژیک، مورفولوژیک، عملکرد دانه و صفات وابسته به آن در مقایسه با قطع آبیاری از مرحله خورجین­ دهی در گیاه کلزا داشت.

This study analyzed the vertical distribution of gravimetric water content (GWC), relative water content (RWC), and equivalent water thickness (EWT) in winter wheat during heading and early ripening stages, and evaluated the position of leaf number at which Vegetation Indexes (VIs) can best retrieve canopy water-related properties of winter wheat. Results demonstrated that the vertical distribution of these properties followed a near-bell-shaped curve with the highest values at the intermediate leaf position. GWC of the top three or four leaves during the heading stage and the top two or three leaves during the early ripening stage can represent the GWC of the whole canopy, but the RWC and EWT of the whole canopy should be calculated based on the top four leaves. At leaf level, the analysis demonstrated strong relationships between EWT and VIs for the top leaf layer, but for GWCD, GWCF, and RWC, the strongest relationships with VIs were found in the intermediate leaf layers. At canopy level, VIs provided the most accurate estimation of GWCfor the top three or four leaves. Water absorption-based VIs could estimate canopy EWT of winter wheat for the top four leaves, but the suitable bands sensitive to water absorptions should be carefully selected for the studied species.

به منظور ارزیابی ویژگی­های زراعی و برخی صفات فیزیولوژیک ارقام کلزا تحت تأثیر تنش خشکی آزمایشاتی به صورت جداگانه در سال زراعی 91-1390 در مزرعه پژوهشی مرکز تحقیقات کشاورزی و منابع طبیعی یزد انجام گرفت. هر آزمایش در قالب طرح پایه بلوک­های کامل تصادفی در سه تکرار بود. آزمایش اول،(شاهد) آبیاری براساس 80 میلی­متر تبخیر از تشتک تبخیر کلاس A در کلیه مراحل رشدی گیاه، آزمایش دوم، تنش خشکی از مرحله ساقه­ دهی تا رسیدگی فیزیولوژیک، آزمایش سوم، تنش خشکی از گلدهی تا رسیدگی فیزیولوژیک و آزمایش چهارم، تنش خشکی از مرحله خورجین ­دهی تا پایان رسیدگی فیزیولوژیک در ارقام GKH2005، Opera و Okapi بودند. نتایج تجزیه مرکب نشان داد قطع آبیاری از مرحله ساقه­ دهی، گل­دهی و خورجین­ دهی به ­ترتیب سبب کاهش معنی­دار 44، 34 و 9 درصدی تعداد خورجین در ساقه اصلی، 60، 34 و 17 درصدی تعداد خورجین در شاخه­ های فرعی، 62، 35 و 5 درصدی تعداد دانه در خورجین ساقه اصلی، 73، 46 و 11 درصدی تعداد دانه در خورجین شاخه­ های فرعی، 19، 28 و 26 درصدی وزن هزار دانه و 62، 51 و 27 درصدی عملکرد دانه در مقایسه با شاهد گردید. بیشترین عملکرد دانه در آزمایش شاهد، به میزان 3110 کیلوگرم در هکتار، و پس از آن به ­ترتیب در آزمایش­ های قطع آبیاری از خورجین­ دهی، گل­دهی و ساقه ­دهی به میزان 2510،1773 و1450 کیلوگرم در هکتار بود. تنش خشکی سبب کاهش هدایت روزنه ­ای، محتوای نسبی آب برگ و پایداری غشاء سلولی شد، در حالی که عدد SPAD را افزایش داد. در بین ارقام مورد بررسی، رقم GKH در شرایط تنش خشکی با کمترین درصد نشت الکترولیت­ها­، هدایت روزنه ­ای و محتوای نسبی آب برگ بالا، از بالاترین تعداد خورجین، تعداد دانه در خورجین و عملکرد دانه برخوردار بود. نتایج کلی این آزمایش نشان داد که اعمال قطع آبیاری از مرحله خورجین­ دهی به دلیل کاهش تعداد دفعات آبیاری و استفاده بهینه از آن در آبیاری محصولات تابستانه همراه با استفاده از ارقام متحمل به خشکی، می­تواند در افزایش بهره­وری و سطح زیر کشت کلزا در مناطق خشک و نیمه خشک مؤثر باشد.

The effect of salt stress on some physiological traits of wheat (Triticum aestivum L.) was studied under growth chamber condition in a factorial experiment based on completely randomized design with three replications. Salinity treatments carried out in three levels (0.0, 50.0 and 100.0 mM) NaCl. Three wheat landraces (white heteyeh, black heteyeh and Norsi.) were studied. Relative leaf water content (RWC), chlorophyll content (SPDA), plant fresh weight and plant dry weight were measured at seedling stage. Salinity stress decreased relative water content (RWC), whereas chlorophyll content, fresh weight and dry weight were not affected. Based on the obtained results “Norsi” may be considered as the most tolerant landrace, since it showed the lowest reduction percent in LRWC under 50 and 100 mM NaCl. [ABSTRACT FROM AUTHOR]

There have been studies on the effect of water stresses on leaf stomatal conductance (g s ); however, the scientific reports on using non-contact techniques such as thermography for sesame ( Sesamum indicum L.) are rare. The objectives of this study were hence to detect water status in sesame (genotype, “Naz-Takshakhe”) under greenhouse conditions using Crop Water Stress (CWSI) and stomatal conductance (I g ) Indices. One hundred and fifty pots were randomly assigned to three equal groups which were irrigated at soil water potential of −0.1 MPa (well-watered, WW), −1.0 MPa (moderate-water stressed, MWS), and −1.5 MPa (severe-water stressed, SWS). Four formulations of CWSI and two of Ig using canopy temperature (T C ) from the WW treatment or temperature from a wet reference for the upper threshold and T C from the SWS treatment, temperature from a dry reference or air temperature plus 3° as the lower threshold were compared. Moreover, an additional CWSI and Ig formulations were also obtained by non-water stress baseline (NWSB) information using meteorological data. Furthermore, the relative water content (RWC) and g s were measured on the youngest and uppermost fully developed leaves of each pot. T C of MWS and SWS plants was higher than WW plants by 1.9 and 2.6 °C, respectively. A significant and linear relationship ( P <  0.001) between CWSI/I g and g s /RWC was found. Therefore, both physiological traits of g s and RWC can be estimated by temperature-based indices of CWSI/I g . The results also showed the developed system enables us to estimate actual time variations in canopy temperatures. This study validates the effectiveness of using CWSI/I g for non-destructive detection of water stress and estimation of relative water content in sesame. [ABSTRACT FROM AUTHOR]

The effects of iron nanoparticles and salicylic acid (SA) on strawberry (Fragaria × ananassa Duch.) plants in conditions of drought stress were surveyed under in vitro conditions to find the optimum combination for strawberry tissue culture. Cuttings of the Queen Elisa cultivar were surveyed in a three-way factorial experiment with three replications in 2015. The results showed that drought stress significantly affected all measured parameters of strawberry plantlets under in vitro condition in a negative way. SA compensated for the negative effects of drought stress on strawberry plantlets and improved their growth parameters under in vitro culture. Strawberry plantlets treated with iron nanoparticles were able to cope with stressful conditions better than untreated ones. This study found that iron, a micronutrient in plant growth and in vitro development, greatly influenced the plantlets’ growth parameters and other measured traits. These results indicate that the efficiency of tissue culture and in vitro culture of strawberries could be improved by increased application of iron in the form of nanoparticles. The results might also indicate that the application of iron nanoparticles along with SA can be a useful method for providing higher quantity and quantity in the in vitro culture of strawberries, and could be used for adapting strawberry plants to drought before transplanting them in the field. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) symbiosis is known to help the host plant to overcome environmental stresses as drought by a combination of multiple mechanisms including enhancing of root water uptake capacity. On the other hand, Nitric oxide (NO) is involved in regulating the response of plants to environmental stresses and colonization process of AM fungi. The objective of this research was to study how AM and non-AM lettuce plants responded to a NO donor (sodium nitroprusside; SNP) or to a NO synthesis inhibitor (Nω-nitro-L-arginine methyl ester hydrochloride; L-NAME) under well watered and drought conditions. Most remarkable results were that L-NAME increased the percentage of AM colonized roots under both water regimes and AM plants modified the shoot:root ratio by both chemicals under well watered conditions. Also, the deleterious effects of SNP treatment were partially prevented by AM symbiosis. Moreover, NO could be involved in the diminution of leaf water content under drought conditions, and SNP treatment seems to favor apoplastic water path inside roots. Therefore, different outcomes of relative water content, stomatal conductance and root hydraulic conductivity observed between AM and non-AM plants could be mediated by NO. [ABSTRACT FROM AUTHOR]

Eucalyptus (E.camaldulensis Dehnh) is one of the major plant species in Iran covering vast areas of plantations. This is a fast-growing species with high tolerance to harsh environmental conditions. Nevertheless the water deficiency in soil can be effective on the quality and quantity of plant growth. To study the effect of soil drought stress on water relationship in Eucalyptus (E.camaldulensis Dehnh), an experiment was carried out using weight and drainage Lysimeters in natural condition. The trials were implemented in Shahid Sadoghi control desert research station inYazd for three years. The experiment was done with three treatments, 100% (control), 70% (medium stress) and 40% (high stress) field capacity (FC) in three replicates as complete randomize design. The results showed that the plant physiological behaviors including water potential, relative water content (RWC) and soluble sugar in leaves were affected by water availability for plant. Increasing the amount of soil moisture was not significantly effective on soluble sugar levels in roots and leaves proline levels (P-value> 0.05). By increasing the amount of soil moisture, the relative water content (P-value

In rice, several cultivated and upland varieties need to be assessed and analyzed for drought tolerance traits which could be used in screening and breeding programs for drought tolerance. Hence, the objectives of this study were to investigate the effects of water deficits in two rice cultivars and thereby analyze the role of several physiological traits useful in rice breeding programs for drought tolerance. The rice varieties Tellahamsa (TH) and N22 were screened for tolerance to drought. A comparative study was done subjecting them to PEG mediated water stress. Accumulation of solutes, i.e., proline, total free aminoacids and sugars; biomass production, Relative Water Content (RWC) and the levels of antioxidant enzymes, viz., Catalase (CAT), Ascorbate Peroxidase (APX), Glutathione Reductase(GR), and Superoxide Dismutase(SOD) were analyzed in response to water stress. Maximum proline accumulation was seen within 24hrs of stress, after 10 days TH decreased its proline to one-third, whereas in N22 doubled. Although amino acids doubled within 24hrs, gradually they depleted in N22. This may be due to conversion of aminoacids into proline which could be the most compatible solute. Sugars increased within 24hrs, but were depleted in 10days in both. In TH, the shoot and root biomass decreased, whereas in N22 there was a significant increase in root biomass. Shoot and root RWC of N22 was higher than TH under stress. GR increased in both TH and N22, APX and SOD increased only in N22. Proline accumulation, increase of root biomass and antioxidant enzymes such as APX or SOD during water stress are contributing to drought tolerance and could be used in screening for drought tolerance. [ABSTRACT FROM AUTHOR]

The aim of the present study is to evaluate the effect of drought stress on the antioxidant enzyme activities including catalase (CAT) and superoxide dismutase (SOD) in Hordeum vulgare. Antioxidant marker proline and water relative content (RWC) were also investigated. Pot experiments were performed in four treatments depending on the irrigation period. Control plants were irrigated once every two days whereas drought was induced by withholding water for 5 days, 9 days and 12 days. A total of 16 pots were used with 4 pots for each treatment. The results showed that water stress imposed by the different periods of irrigation induced a significant decrease on relative water content (RWC). The effect of water deficit by delaying the period of irrigation was strongly marked on high proline accumulation. The SOD and CAT activities were slightly increased in plants irrigated after 5 days, 9 days and 12 days when compared to control. [ABSTRACT FROM AUTHOR]

Five tomato (Solanum lycopersicum L.) genotypes, including heat tolerant (Pusa Sadabahar, Booster, Pusa Sheetal), one F1 combination (Pusa Sheetal × Pusa Sadabahar ) and one susceptible genotype (Pusa Rohini) were grown under phytotron under four temperature regimes, i.e. 20/24, 22/26, 24/32, 27/37°C night (11 hours)/day (13 hours) temperature, respectively. Pusa Sadabahar and Booster recorded high value of relative water content (RWC) and low value of membrane injury index (MII) both at normal and high temperature conditions. High value of chlorophyll a and chlorophyll b ratio was recorded in Pusa Sadabahar and Pusa Sheetal×Pusa Sadabahar under all the temperature regimes showed their tolerance to high temperature. Normal (more than 80 percent) flowering and fruiting was recorded in all the genotypes at 20/24°C & 22/26°C. However at 24/32°C Pusa Sadabahar recorded 65 per cent fruit set and other genotypes 25 to 49 percent fruit setting only. None of the genotypes could record fruit set at 27/37°C, except Pusa Sadabahar which could set few small fruits (19%). Pollen germination was maximum (ranging from 21.8 - 62.9%) in Pusa Sadabahar under all temperature regimes. The susceptible genotype, Pusa Rohini recorded exerted stigma in 100% flowers at 27/37°C temperature whereas it was 75% in tolerant genotype Pusa Sadabahar. Night/day temperature 22/26°C was optimum for fruit set, pollen viability and normal stigma development in tomato. High night temperature (³ 26°C ± 2°C) at flowering was the major factor in reducing fruit set in tomato than the day temperature. The study showed that day temperature of ³ 35°C and night temperature of ³ 26oC may be used for screening tomato against high temperature tolerance.

In this study, we comparatively evaluated the effects of the flurochloridone as well as flurochloridone and exogenously applied salicylic acid (SA) on Helianthus annuus L. to find out herbicide-induced toxicity reducing influence of SA. We examined and compared the physiological and biochemical effects of different concentrations of flurochloridone (11, 32 and 72mM) in both the SA pre-treated and non-treated plants. The plants treated with flurochloridone exhibited reduced total chlorophyll, carotenoid, and relative water content compared to the control group, whereas the plants that were pre-treated with SA exhibited relatively higher values for the same physiological parameters. In the SA non-treated plants, the superoxide dismutase, glutathione reductase and glutathione S-transferase activities were increased in the treatment groups compared to the control group. In the treatment groups, these enzyme activities were decreased in the SA-pre-treated plants compared to the non-treated plants. Ascorbate peroxidase and catalase activities decreased in the flurochloridone-treated plants compared to the control plants. The ascorbate peroxidase activity increased in the control groups but decreased in the treatment groups in the SA pre-treated plants compared to the non-treated plants. However, SA treatment decreased the activity of catalase in the control and treatment groups compared to the plants that were not treated with SA. Flurochloridone treatment increased the malondialdehyde content in the treated groups compared to the control groups, whereas SA-pretreatment decreased malondialdehyde content compared to plants that were not treated with SA. Flurochloridone treatment increased endogenous SA content compared to the control. Although the residual levels of herbicide in the plants increased proportionately with increasing herbicide concentrations, the SA-pre-treated plants exhibited reduced residual herbicide levels compared to the plants that were not treated with SA. These results indicate that the flurochloridone induces various physiological and biochemical responses in non-target plants and that treatment with exogenous SA can increase stress resistance by altering these responses. [Copyright &y& Elsevier]

Abstract: The unique response of desiccation-tolerant, or resurrection plants, to extreme drought is accompanied by major changes in the protein pool, raising the possibility of the involvement of proteases. We detected and characterized proteases present in their active state in leaf extracts of desiccated Ramonda serbica Panč., a resurrection plant from the Balkan Peninsula. Plants desiccated under laboratory conditions and maintained in anhydrobiosis for 4 and 14 months revived upon rehydration. Protease activities were determined spectrophotometrically in solution and by zymography on gels. Several endo- and aminopeptidases were detected and characterized by their pH profiles. Their enzyme class was determined using specific inhibitors. Those with higher activities were a serine endopeptidase active against Bz-Arg-pNA with a pH optimum around 9, and aminopeptidases optimally active at pHs from 7 to 9 against Leu-pNA, Met-pNA, Phe-pNA, Pro-pNA and Ala-pNA. The levels of their activities in leaf extracts from desiccated plants were significantly higher than those from rehydrated plants and from regularly watered plants, implying their involvement in the recovery of vegetative tissues from desiccation. [Copyright &y& Elsevier]

Abstract: The work explored sucrose metabolism in the leaves subtending the cotton boll (SBL) and its role in boll weight after waterlogging in cotton. Results showed that net photosynthesis rate (Pn), relative water content, contents of Chlorophyll a and Chlorophyll b, initial ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) activity and cytosolic fructose-1, 6-bisphosphatase (cy-FBPase) activity decreased with waterlogging in the SBL on fruiting branches 2–3 (FB2–3) and FB6–7. Activities of sucrose synthase (SuSy) and sucrose phosphate synthase (SPS) increased to the maximum up to 6 days of waterlogging then decreased with prolonged waterlogging. Rubisco activation and specific leaf weight increased and gene expressions of SuSy, SPS and rubisco activase (RCA) were all up-regulated with the duration of waterlogging, especially for the SBL on FB6–7. The induction of activity and gene expression of SuSy was most significant indicating its crucial role in sucrose metabolism after waterlogging. For the SBL in the later period of boll development on upper FB10–11 and FB14–15, the pattern seemed opposite to that of FB2–3 and FB6c7 as compensation effect in vegetative growth existed. Correlation analysis revealed that initial Rubisco activity and cy-FBPase activity were the main limitation to Pn reduction after waterlogging. Reduction in Pn, sucrose transformation rate and initial Rubisco activity directly decrease boll weight in waterlogged cotton. Besides the role in sucrose metabolism after waterlogging, SuSy also had a positive significant correlation with the duration of rapid-accumulation period for seed fiber weight (P <0.05). These findings elucidated mechanisms to waterlogging that affected seed fiber weight, which resulted from alteration in carbohydrates, enzymes and genes. [Copyright &y& Elsevier]

Highlights: [•] Biochar effects on yield and quality of tomato were studied under different irrigations. [•] Biochar enhanced soil water storage under reduced irrigation (DI and PRD). [•] PRD, in combination with biochar produced almost same yield as FI. [•] PRD, in combination with biochar may be used to enhance crop water use efficiency. [ABSTRACT FROM AUTHOR]

Abstract: Experiments were conducted to evaluate the effects of combined water salinity and deficit irrigation on common bermudagrass in order to address the shortage of water resources and increasing water and soil salinity in arid and semi-arid zones. This study was carried out under greenhouse conditions in a completely randomized design with factorial arrangements. Treatments included 4 water salinity levels (0.5, 3, 6 and 9dSm−1) and 4 deficit irrigation regimes (2, 4, 6 and 8day intervals). Results indicated a rise in ion leakage, soluble sugars and proline concentrations; and a drop in leaf relative water content (RWC), leaf chlorophyll content and photosynthetic rate with increasing levels of both stresses. Antioxidant enzymes, superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), peroxidase (POD, EC 1.11.1.7) and ascorbate peroxidase (APX, EC 1.11.1.11) showed higher activity under moderate drought or salinity conditions. However, these enzyme levels dropped at higher levels of these two stresses. Based on the results of the present study, common bermudagrass could be grown under moderate combined water and salinity stresses without considerable damage to plants at the physiological and/or biochemical level. This is the first report of applying combined water and salinity stresses to an important turfgrass species. Further studies are needed to evaluate the effects of these stresses on characteristics of bermudagrass at the molecular and ultrastructural levels. [Copyright &y& Elsevier]

Highlights: [•] Glycoside treatments improve leaves and roots growth and development. [•] In water stress condition glycoside treatments increase root/shoot ratio. [•] It alleviated drought effect: enhances photosynthetic rate and water use efficiency. [•] Glycosides application mitigated reduction of ΦPS II and ETR, caused by water stress. [•] Treatment induced an enhancement of non-photochemical processes in drought condition. [ABSTRACT FROM AUTHOR]

Abstract: The transcript expression of a gene SrUGT85C2 has been documented for direct relation with steviol glycoside content in Stevia plant. Steviol glycoside and gibberellin biosynthetic routes are divergent branches of methyl erythritol-4 phosphate (MEP) pathway. So, SrUGT85C2 might be an influencing gibberellin content. Hence in the present study, transgenic Arabidopsis thaliana overexpressing SrUGT85C2 cDNA from Stevia rebaudiana was developed to check its effect on gibberellin accumulation and related plant growth parameters. The developed transgenics showed a noteworthy decrease of 78–83% in GA3 content. Moreover, the transgenics showed a gibberellin deficient phenotype comprising stunted hypocotyl length, reduced shoot growth and a significant fall in relative water content. Transgenics also showed 17–37 and 64–76% reduction in chlorophyll a and chlorophyll b contents, respectively. Reduction in photosynthetic pigments could be responsible for the noticed significant decrease in plant biomass. Like steviol glycoside and gibberellin biosynthesis, chlorophyll biosynthesis also occurs from the precursors isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) of MEP pathway in the plastids. The observed downregulated expression of genes encoding MEP pathway enzymes geranyl geranyl diphosphate synthase (GGDPS), copalyl diphosphate synthase (CDPS), kaurenoic acid oxidase (KAO), chlorophyll synthetase and chlorophyll a oxygenase in transgenics overexpressing SrUGT85C2 might be responsible for the reduction in gibberellins as well as chlorophyll. This study has documented for the first time the regulatory role of SrUGT85C2 in the biosynthesis of steviol glycoside, gibberellins and chlorophyll. [Copyright &y& Elsevier]

Abstract: Osmotic stress responses of water content, photosynthetic parameters and biomass production were investigated in wheat-Aegilops biuncialis amphiploids and in wheat genotypes to clarify whether they can use to improve the drought tolerance of bread wheat. A decrease in the osmotic pressure of the medium resulted in considerable water loss, stomatal closure and a decreased CO2 assimilation rate for the wheat genotypes, while the changes in these parameters were moderate for the amphiploids. Maximal assimilation rate was maintained at high level even under severe osmotic stress in the amphiploids, while it decreased substantially in the wheat genotypes. Nevertheless, the effective quantum yield of PS II was higher and the quantum yield of non-photochemical quenching of PS II and PS I was lower for the amphiploids than for the wheat cultivars. Parallel with this, higher cyclic electron flow was detected in wheat than in the amphiploids. The elevated photosynthetic activity of amphiploids under osmotic stress conditions was manifested in higher biomass production by roots and shoots as compared to wheat genotypes. These results indicate that the drought-tolerant traits of Ae. biuncialis can be manifested in the wheat genetic background and these amphiploids are suitable genetic materials for improving drought tolerance of wheat. [Copyright &y& Elsevier]

Highlights: [•] ABA pretreatment effects in U. minor growth and antioxidant capacity were analyzed. [•] ABA reduces water loss and increases plant growth under WW and WS conditions. [•] ABA increases WS tolerance by prevention of oxidative membrane damages. [•] ABA delays S-phase and increases FPCV. [•] ABA pretreatment could be a strategy to decrease the negative effect of WS. [ABSTRACT FROM AUTHOR]

Highlights: [•] Stay-green effect occurred in individuals under drought conditions. [•] Chlorophyll content, at senescence, was negatively correlated with final tuber yield. [•] Senescence rate was lower in the treatments with higher water restriction. [Copyright &y& Elsevier]

Highlights: [•] Drought stress reduced evapotranspiration, RWC, ψ l , ψ π , ψ p , g s , and leaf area. [•] Recovery of g s was faster in ‘Titania’ than in ‘Ben Hope’ upon rewatering. [•] Root growth remained more inhibited in ‘Titania’ than ‘Ben Hope’ during recovery. [•] The cultivar ‘Ben Hope’ responded to less severe drought stress than ‘Titania’. [•] Drought stress reduced the number of strigs and flowers per node in ‘Ben Hope’. [Copyright &y& Elsevier]

Summary: The behaviour of tomato plants inoculated with arbuscular mycorrhizal (AM) fungi grown in the presence of aqueous extracts from dry olive residue (ADOR) was studied in order to understand how this symbiotic relationship helps plants to cope with oxidative stress caused by ADOR. The influence of AM symbiosis on plant growth and other physiological parameters was also studied. Tomato plants were inoculated with the AM fungus Funneliformis mosseae and were grown in the presence of ADOR bioremediated and non-bioremediated by Coriolopsis floccosa and Penicillium chrysogenum-10. The antioxidant response as well as parameters of oxidative damage were examined in roots and leaves. The data showed a significant increase in the biomass of AM plant growth in the presence of ADOR, regardless of whether it was bioremediated. The establishment and development of the symbiosis were negatively affected after plants were exposed to ADOR. No differences were observed in the relative water content (RWC) or PS II efficiency between non-AM and AM plants. The increase in the enzymatic activities of superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6) and glutathione-S-transferase (GST; EC 2.5.1.18) were simultaneous to the reduction of MDA levels and H2O2 content in AM root growth in the presence of ADOR. Similar H2O2 levels were observed among non-AM and AM plants, although only AM plants showed reduced lipid peroxidation content, probably due to the involvement of antioxidant enzymes. The results highlight how the application of both bioremediated ADOR and AM fungi can alleviate the oxidative stress conditions, improving the growth and development of tomato plants. [Copyright &y& Elsevier]

Abstract: Ramie (Boehmeria nivea L.) is one of the oldest and most important fiber crops in China due to the comfortable textile of its fine fiber. Increased ramie fiber demand brings ramie cultivation to salt-affected regions. The aim of this research was to determine morphological, physiological and biochemical responses of ramie by subjecting plants to varying concentrations of NaCl (0, 2, 4, 6 and 8 g NaCl/kg dry soil) at vigorous growth stage for 10 and 20 days. Results indicated that salinity stress substantially inhibited the growth of hybrid ramie plants and led to remarkable decline in fiber yield. However, when grown at 2 g NaCl/kg growth and fiber yield were similar to non-saline control. In addition, chlorophyll fluorescence and gas exchange parameters were correlated with growth and yield response. Salt treatments promoted a subsequent decrease in maximum quantum efficiency of PSII photochemistry (Fv/Fm), quantum efficiency of open PSII reaction centers (Fvʹ/Fmʹ) and quantum yield of PSII (φ PSII) while non-photochemical quenching (NPQ) changed conversely. Photochemical quenching (qP) and electron transport rate of PSII (ETR) increased at 2 and 4 g NaCl/kg then decreased at 6 and 8 g NaCl/kg. Substantial decline in the PSII activity at high salinity was associated with the loss of chlorophyll contents. Moreover, marked decrease in net photosynthetic rate (A), transpiration rate (E), stomatal conductance (g s ) was also recorded. Nonetheless, intercellular CO2 (Ci) decreased at low salt stress, subsequently increased at high salt stress while water use efficiency (WUE) and instantaneous water use efficiency (WUEi) altered in opposite direction. Substantial decrease of photosynthesis at high salinity was due to non-stomatal factors. Furthermore, salinity stress led to decrease of proteins and accumulation of proline and malondialdehyde (MDA), as well as enhanced activities of superoxide dismutase (SOD, EC 1.15.1.1) and peroxidase (POD, EC 1.11.1.6), whereas, catalase (CAT, EC 1.11.1.7) enhanced at low salinity, decreased at high salinity. Nonetheless, these changes were closely related with the severity and duration of the salinity stress and their interaction. The results suggested a certain tolerance to salinity stress for hybrid ramie. This meets the essential condition for utilization in salinity-prone environments. [Copyright &y& Elsevier]

Abstract: The accumulation of putrescine (Put) and increased arginine decarboxylase (ADC, EC 4.1.1.19) activity levels in response to osmotic stress has been reported; however, the biological meaning of this increase remains unclear. To obtain new insights into these questions, we studied the drought response of a transgenic Lotus tenuis line that expresses the oat ADC gene, which is driven by the stress-inducible pRD29A promoter. This line contains high levels of Put with no changes in spermidine and spermine contents, even under water deficits. Our results indicate that the biochemical and morphological responses to dehydration correlate with the Put level and provide evidence that Put controls the ABA content in response to drought by modulating ABA biosynthesis at the transcriptional level. [Copyright &y& Elsevier]

Abstract: Adaptation to salinity of a semi-arid inhabitant plant, henna, is studied. The salt tolerance mechanisms are evaluated in the belief that gas exchange (water vapor and CO2) should play a key role on its adaptation to salt stress because of the strong evaporation conditions and soil water deficit in its natural area of distribution. We grow henna plants hydroponically under controlled climate conditions and expose them to control (0mM NaCl), and two levels of salinity; medium (75mM NaCl) and high (150mM NaCl). Relative growth rate (RGR), biomass production, whole plant and leaf structure and ultrastructure adaptation, gas exchange, chlorophyll fluorescence, nutrients location in leaf tissue and its balance in the plant are studied. RGR and total biomass decreased as NaCl concentration increased in the nutrient solution. At 75mM NaCl root biomass was not affected by salinity and RGR reached similar values to control plants at the end of the experiment. At this salinity level henna plant responded to salinity decreasing shoot to root ratio, increasing leaf specific mass (LSM) and intrinsic water use efficiency (iWUE), and accumulating high concentrations of Na+ and Cl− in leaves and root. At 150mM NaCl growth was severely reduced but plants reached the reproductive phase. At this salinity level, no further decrease in shoot to root ratio or increase in LSM was observed, but plants increased iWUE, maintaining water status and leaf and root Na+ and Cl− concentrations were lower than expected. Moreover, plants at 150mM NaCl reallocated carbon to the root at the expense of the shoot. The effective PSII quantum yield [Y(II)] and the quantum yield of non-regulated energy dissipation [Y(NO)] were recovered over time of exposure to salinity. Overall, iWUE seems to be determinant in the adaptation of henna plant to high salinity level, when morphological adaptation fails. [Copyright &y& Elsevier]

Abstract: Drought stress is one of the most frequent forms of abiotic stresses, which occurs under condition of limited water availability. In this work, the possible participation of phosphoenolpyruvate carboxylase (EC 4.1.1.31; PEPC), NADP-malic enzyme (EC 1.1.1.40; NADP-ME), and pyruvate, phosphate dikinase (EC 2.7.9.1; PPDK) in response to drought of tobacco plants (Nicotiana tabacum L., cv. W38) was investigated. Enzyme specific activities in tobacco leaves of drought stressed plants were significantly increased after 11 days of stress, PEPC 2.3-fold, NADP-ME 3.9-fold, and PPDK 2.7-fold compared to control plants. The regulation of PEPC and NADP-ME activities were studied on transcriptional level by the quantitative RT PCR and on translational level – immunochemically. The amount of NADP-ME protein and transcription of mRNA for chloroplastic NADP-ME isoform were increased indicating their enhanced synthesis de novo. On the other hand, mRNA for cytosolic isoform of NADP-ME was decreased. The changes in PEPC protein and PEPC mRNA were not substantial. Therefore regulation of PEPC activity by phosphorylation was evaluated and found to be involved in the stress response. During recovery, activities of the tested enzymes returned close to their basal levels. [Copyright &y& Elsevier]

Abstract: Dehydration responsive element binding (DREB) transcription factors play an important role in the regulation of stress-related genes. These factors contribute to resistance to different abiotic stresses. In the present study, a novel DREB transcription factor, BdDREB2, isolated from Buchloe dactyloides, was cloned and characterized. The BdDREB2 protein was estimated to have a molecular weight of 28.36kDa, a pI of 5.53 and a typical AP2/ERF domain. The expression of BdDREB2 was involved in responses to drought and salt stresses. Overexpression of BdDREB2 in tobacco showed higher relative water and proline content, and was associated with lower MDA content under drought stress, suggesting that the transgenic tobacco may tolerate drought stress better. Results demonstrate that BdDREB2 may play an important role in the regulation of abiotic stress responses, and mediate many physiological pathways that enhance stress tolerance in plants. [Copyright &y& Elsevier]

Highlights: [•] Air exposure induces a desiccation stress condition in intertidal seaweed species. [•] High activities of antioxidant enzymes and low ROS production were the responses in higher intertidal species. [•] Photosynthesis capacity was recovered during rehydration only in higher intertidal species. [•] Lower intertidal distribution of certain algal species is explained by their insufficient mechanisms of stress tolerance. [ABSTRACT FROM AUTHOR]

Abstract: During the last decade we showed clearly that abiotic stress changes the cellular composition of polyamines, which in turn regulate the photochemical and non-photochemical quenching of the received light energy in the photosynthetic apparatus and that modulate substantially the level of plant tolerance. In the present contribution, we tried to change the bioenergetics of the leaf discs before the exposure to osmotic stress only by exogenously supplied putrescine, in order to enhance quickly the tolerance against the abiotic stress. Tobacco leaf discs treated with polyethylene-glycol reduced their water content about 24% within 1h. This relatively mild osmotic stress increased endogenous putrescine about 83% and decreased maximum photosystem II photochemical efficiency about 14%. In line with this, here we show that treatment with 1mM exogenous putrescine 1h before polyethylene-glycol addition protects the photochemical capacity and inhibits loss of water, confirming the key role of putrescine in the modulation of plant tolerance against osmotic stress. Furthermore, our recent works indicate that putrescine is accumulated in lumen during light reactions and may act as a permeable buffer and an osmolyte. [Copyright &y& Elsevier]

Abstract: The biochemical responses of the enzymatic antioxidant system of a drought-tolerant cultivar (IACSP 94-2094) and a commercial cultivar in Brazil (IACSP 95-5000) grown under two levels of soil water restriction (70% and 30% Soil Available Water Content) were investigated. IACSP 94-2094 exhibited one additional active superoxide dismutase (Cu/Zn-SOD VI) isoenzyme in comparison to IACSP 95-5000, possibly contributing to the heightened response of IACSP 94-2094 to the induced stress. The total glutathione reductase (GR) activity increased substantially in IACSP 94-2094 under conditions of severe water stress; however, the appearance of a new GR isoenzyme and the disappearance of another isoenzyme were found not to be related to the stress response because the cultivars from both treatment groups (control and water restrictions) exhibited identical changes. Catalase (CAT) activity seems to have a more direct role in H2O2 detoxification under water stress condition and the shift in isoenzymes in the tolerant cultivar might have contributed to this response, which may be dependent upon the location where the excessive H2O2 is being produced under stress. The improved performance of IACSP 94-2094 under drought stress was associated with a more efficient antioxidant system response, particularly under conditions of mild stress. [Copyright &y& Elsevier]

Abstract: Lemon balm (Melissa officinalis, L.; Lamiaceae) was exposed to realistic ozone (O3) dosages (80 ppb for 5 h), because high background levels of O3 are considered to be as harmful as episodic O3 regimes. Temporal alterations of different ecophysiological, biochemical and structural parameters were investigated in order to test if this species can be considered as an O3-bioindicator regarding changes in background concentrations. At the end of ozone exposure, the plants did not exhibit any visible foliar symptoms, as only at microscopic level a small number of dead cells were found. Photosynthetic processes, however, were significantly affected. During and after the treatment, ozone induced a reduction in CO2 fixation capacity (up to 52% after 12 h from the beginning of the treatment) due to mesophyllic limitations. Intercellular CO2 concentration significantly increased in comparison to controls (+90% at the end of the post-fumigation period). Furthermore impairment of carboxylation efficiency (−71% at the end of the post-fumigation period compared to controls in filtered air) and membrane damage in terms of integrity (as demonstrated by a significant rise in solute leakage) were observed. A regulatory adjustment of photosynthetic processes was highlighted during the post-fumigation period by the higher values of qNP and (1-qP) and therefore suggests a tendency to reduce the light energy used in photochemistry at the expense of the capacity to dissipate the excess as excitation energy. In addition, the chlorophyll a/b ratio and the de-epoxidation index increased, showing a rearrangement of the pigment composition of the photosynthetic apparatus and a marked activation of photoprotective mechanisms. [Copyright &y& Elsevier]

Abstract: Seedlings of Cleopatra mandarin (Citrus reshni Hort. ex Tan.) and Alemow (Citrus macrophylla Wester) were inoculated with a mixture of AM fungi (Rhizophagus irregularis and Funneliformis mosseae) (+AM), or left non-inoculated (−AM). From forty-five days after fungal inoculation onwards, half of +AM or −AM plants were irrigated with nutrient solution containing 50mM NaCl. Three months later, AM significantly increased plant growth in both Cleopatra mandarin and Alemow rootstocks. Plant growth was higher in salinized +AM plants than in non-salinized −AM plants, demonstrating that AM compensates the growth limitations imposed by salinity. Whereas AM-inoculated Cleopatra mandarin seedlings had a very good response under saline treatment, inoculation in Alemow did not alleviate the negative effect of salinity. The beneficial effect of mycorrhization is unrelated with protection against the uptake of Na or Cl and the effect of AM on these ions did not explain the different response of rootstocks. This response was related with the nutritional status since our findings confirm that AM fungi can alter host responses to salinity stress, improving more the P, K, Fe and Cu plant nutrition in Cleopatra mandarin than in Alemow plants. AM inoculation under saline treatments also increased root Mg concentration but it was higher in Cleopatra mandarin than in Alemow. This could explain why AM fungus did not completely recovered chlorophyll concentrations in Alemow and consequently it had lower photosynthesis rate than control plants. AM fungi play an essential role in citrus rootstock growth and biomass production although the intensity of this response depends on the rootstock salinity tolerance. [Copyright &y& Elsevier]

Abstract: Cork oak is an economically important forest species showing a great tolerance to high temperatures and shortage of water. However, the mechanisms underlying this plasticity are still poorly understood. Among the stress regulators, transcription factors (TFs) are especially important since they can control a wide range of stress-inducible genes, which make them powerful targets for genetic engineering of stress tolerance. Here we evaluated the influence of increasing temperatures (up to 55 °C) or drought (18% field capacity, FC) on the expression profile of an R2R3-MYB transcription factor of cork oak, the QsMYB1. QsMYB1 was previously identified as being preferentially expressed in cork tissues and as having an associated alternative splicing mechanism, which results in two different transcripts (QsMYB1.1 and QsMYB1.2). Expression analysis by reverse transcription quantitative PCR (RT-qPCR) revealed that increasing temperatures led to a gradual down-regulation of QsMYB1 transcripts with more effect on QsMYB1.1 abundance. On the other hand, under drought condition, expression of QsMYB1 variants, mainly the QsMYB1.2, was transiently up-regulated shortly after the stress imposition. Recovery from each stress has also resulted in a differential response by both QsMYB1 transcripts. Several physiological and biochemical parameters (plant water status, chlorophyll fluorescence, lipid peroxidation and proline content) were determined in order to monitor the plant performance under stress and recovery. In conclusion, this report provides the first evidence that QsMYB1 TF may have a putative function in the regulatory network of cork oak response to heat and drought stresses and during plant recovery. [Copyright &y& Elsevier]