Water Stress Treatments Research Articles

Exploring the relationship between leaf water potential, defoliation, and grape berry physical properties of Merlot (Vitis vinifera L.) grapevine

The aim of this study was to examine the impact of leaf water potential and defoliation treatments on the physical properties of grape berries. The research was conducted over two consecutive years (2019-2020) using ‘Merlot’/41B graft combination grapevines grown in the Chateau Kalpak vineyards located in Tekirdağ, Şarköy. The experiment involved four distinct water stress levels (S0, S1, S2, and S3), which were determined based on leaf water potential measurements. These stress levels were subjected to different irrigation levels. Additionally, defoliation treatments were applied, including Control (C), Full Window (FW), Right Window (RW), and Left Window (LW). The results showed that the effects of water stress and defoliation treatments on berry physical properties were statistically insignificant. However, in the second year of the study, the FW treatment was observed to have led to changes in the desired direction for grapevines. This was likely due to the cumulative decrease in water reserves caused by reduced precipitation over multiple years, making the effects of FW treatment more prominent. Moreover, the study found that both current and past vegetation period conditions influence vine production year, leaf water potentials (Ψleaf), and stress levels. Finally, the data revealed that berry weight and % dry weight increased with higher stress levels.

IMPACT OF POLYETHYLENE GLYCOL-INDUCED OSMOTIC STRESS ON MAIZE GERMINATION, GROWTH, AND PHYSIOLOGICAL RESPONSE

Drought stress is a significant environmental concern affecting crop growth, development, and yield. A laboratory experiment was conducted to examine the germination characteristics of four maize genotypes under varying levels of osmotic stress (0%, 2.5%, 5%, 7.5%, 10%) using polyethylene glycol (PEG) 6000 as an osmoticum. The experiment followed a factorial design within a Completely Randomized Design (CRD) framework with three replications. Varying concentrations of PEG influenced the germination and early growth of plants. An interesting finding was that as the concentration of PEG increased, there was a noticeable decrease in plant growth, indicating a negative correlation between the two. The findings indicated that subjecting maize plants to water stress treatments significantly affected various growth parameters (with a statistical significance level of P<0.05). Furthermore, with the increase in PEG concentration, there was a gradual decline in both respiration and transpiration rates, resulting in a decrease in protein concentration. There is a significant decrease in relative water content (RWC) in both shoot and root by 28.65% and 11.13%, respectively, compared with the control. When maize seedlings were subjected to water deficit by treating them with 2.5 to 10% PEG, there was a significant decrease (by 60.05%) in the level of chlorophyll 'b' while the decrease (by 33.25%) in chlorophyll 'a' content was comparatively less pronounced.

Elevated CO2 concentration increases maize growth under water deficit or soil salinity but with a higher risk of hydraulic failure.

Climate change presents a challenge for plants to acclimate their water relations under changing environmental conditions, and may increase the risks of hydraulic failure under stress. In this study, maize plants were acclimated to two different CO2 concentrations ([CO2]; 400 ppm and 700 ppm) while under either water stress (WS) or soil salinity (SS) treatments, and their growth and hydraulic traits were examined in detail. Both WS and SS inhibited growth and had significant impacts on hydraulic traits. In particular, the water potential at 50% loss of stem hydraulic conductance (P50) decreased by 1 MPa in both treatments at 400 ppm. When subjected to elevated [CO2], the plants under both WS and SS showed improved growth by 7-23%. Elevated [CO2] also significantly increased xylem vulnerability (measured as loss of conductivity with decreasing xylem pressure), resulting in smaller hydraulic safety margins. According to the plant desiccation model, the critical desiccation degree (time×vapor pressure deficit) that the plants could tolerate under drought was reduced by 43-64% under elevated [CO2]. In addition, sensitivity analysis showed that P50 was the most important trait in determining the critical desiccation degree. Thus, our results demonstrated that whilst elevated [CO2] benefited plant growth under WS or SS, it also interfered with hydraulic acclimation, thereby potentially placing the plants at a higher risk of hydraulic failure and increased mortality.

Effect of Water Stress Duration on the Growth Characteristics and Yield Components of Upland Rice Varieties in Kenya

Drought stress is a major problem in upland rice grown areas under rainfed conditions. It affects plant growth and development, and eventually leads to a considerable yield reduction. The study was carried out with the aim of evaluating the effect of drought stress duration on the growth characteristics and yield components of upland rice varieties. The experiment was conducted at the University of Eldoret with Sixteen upland commercial and local rice varieties were used in the study obtained from Kenya and Liberia. Rice plants were subjected to drought stress treatments at tillering and flowering stages in the green house. The experiment was layout in a complete randomized design (CRD) in a split plot arrangement with five treatments and replicated three times. The results of leaf rolling, plant height, days to 50% flowering, days to maturity, panicle number, spikelet sterility, biological yield, leaf relative water content,1000-grain weight, harvest index and grain yield revealed that there were significant differences as a result of water stress on the treatments (p≤0.001) and rice varieties (p≤0.05). All the sixteen varieties were significantly affected by the treatments when compared with the control. The results also revealed that MWUR, Dourado, L-22, Komboka, Jaowo, LAC-23, Kpatawee, MWUR, White rice and Red Youmo varieties were significantly affected by the water stress treatments at leaf rolling, flowering and maturity then that of NERICA 1,2 ,3, 4, 10,11 and 14 at tillering and flowering stages. The findings of this study indicated that NERICA 1, 2, 3, 4, 10 varieties were less affected by soil water stress treatments amongst the tested varieties, followed by NERICA 11 and14 respectively. Thus, NERICA varieties had the best performance in most of the parameters that were measured. Therefore, these varieties can thus be used by breeders to develop varieties adapted to areas with limited rain fall and insufficient soil moisture for rice production.

Amending Soil with Rhizobium carrying Biochar Ameliorates Drought Stress on Phaseolus vulgaris

As a consequence of climate change/global warming earth’s agriculture output is under rigorous stress. There is a growing need to develop strategies to cope with these abiotic stresses. Biochar exhibiting many beneficial qualities appeared to alleviate these problems by improving soil fertility by adding carbon and preventing nutrient losses etc. Biochar can also enhance BNF and could be used as a carrier for rhizobium by providing a suitable microenvironment. The current study is aimed to find the ameliorative potential of different biochar types to be used as rhizobium carriers for Phaseolus vulgaris L. exposed to drought stress. Both types of biochar were analyzed for physico-chemical and morphological parameters. Presence of Silicon content remains the key finding for rice husk biochar which was absent in Lantana biochar. Increased C, K, and Ca weight percentages were found in Lantana biochar as compared to their proportions for rice husk biochar. On the contrary, the oxygen content was higher in rice husk biochar as compared to that in Lantana. Phaseolus seeds were used for the pot experiment where stress treatment was applied by FTSW (Fractionable Transpirable Soil Water) technique. One isolated strain along with two types of biochar carrier was applied to the plants in combination with water stress treatment. Plants were analyzed for growth and physiological parameters including plant height, leaf area, biomass, photosynthesis, transpiration rate, stomatal conductance, and water use efficiency, where rice husk biochar responded better than the one obtained from Lantana. Plants responded positively for all the growth as well as physiological parameters when treated in combination with the inoculum for both stress levels i.e., 100% and 60% field capacity F.C. The present study advocates rice husk biochar for its ability to enhance tolerance in Phaseolus against drought stress through its role as an inoculum carrier contributing suitable habitat for the microorganism.

The role of stress factors in severity of Cytospora plurivora in greenhouse and field plantings of 13 peach (Prunus persica) cultivars.

Understanding the host-pathogen-environmental interactions in a pathosystem is essential for management of diseases and diminished crop yields. Abiotic stressors such as cold damage, water deficit, and high pH soils can be major limiting factors to tree fruit production. Along with decreased yields, these abiotic factors can have direct implications for disease severity within orchards. Cytospora plurivora is a ubiquitous fungal canker pathogen in western Colorado, USA and is a major focus in integrated pest management strategies. This research evaluated the influence of biotic and abiotic stress factors on peach tree health. Thirteen peach cultivars were placed under abiotic stress and inoculated with C. plurivora in greenhouse and field conditions. Under deficit irrigation, C. plurivora infections were significantly larger and more severe in both the greenhouse and field trials when compared with those under the full-irrigation controls. In controlled greenhouse conditions, a positive correlation between lesion size and water potential was evident, but no trend of cultivar tolerance was observed. Furthermore, increase in irrigation water pH, through additions of sodium carbonate and bicarbonate, in the greenhouse trials resulted in decreased leaf water potentials and increased pathogen necrotic tissue volumes (mm3). In field trials, there was no positive relationship between lesion size and water potential; trees with the most negative water potentials had the smallest lesions sizes that did not correspond to cultivar, suggesting that other abiotic or biotic factors may be shielding water stressed trees from increased pathogen aggression. This research highlights the importance of proper irrigation and soil pH management as tools for the management of Cytospora canker in peach orchards.

The effect of irrigation management on rice grain yield, irrigation water productivity and methane emissions in northern Iran

AbstractThis experiment aims to study the effect of water‐saving irrigation on rice production and methane emissions. Three irrigation methods, that is, flooding irrigation, deficit irrigation (DI) and alternate partial root‐zone drying (APRD), were employed in a 2‐year field trial. The experiment was conducted in a randomized complete block design with three replications. For the DI and APRD treatments, plots were not irrigated until the soil matric potential reached −10 (DI10 and APRD10), −30 (DI30 and APRD30) and −60 kPa (DI60 and APRD60). In the APRD treatments, two adjacent furrows of each plant row were alternately irrigated in consecutive irrigation events. The DI and APRD treatments did not affect yield components when the soil matric potential was −10 kPa. Applying APRD treatments increased irrigation water productivity by 45%, 51% and 31% for soil matric potentials of −10, −30 and −60 kPa, respectively. On average, water stress treatments reduced methane emissions by 78% compared to flooding treatment. On average, the APRD treatments decreased the water input by 10% compared with the DI treatments while achieving a 2.5% higher yield. This is the first study to outline the effect of APRD on methane emissions and rice production. These findings suggest that APRD could be a valuable strategy to mitigate methane emissions without risking rice yield reduction.

Response of Water Stress and Bacterial Fertilizer Addition to the Structure of Microbial Flora in the Rhizosphere Soil of Grapes Under Delayed Cultivation

ABSTRACT The objectives of this study were to reveal the soil microbial structures in the rhizosphere soil of the delayed cultivation and to evaluate the effects of water stress and bacterial fertilizer on major bacteria. The experiment was conducted in 2019 in Yongdeng County, Gansu Province. Three treatments of water regulation were set, including the moderate water stress, mild water stress and adequate water supply treatment with the bacterial fertilizer added at the levels of no addition (0 g), small addition (75 g) and large addition (150 g), respectively. The results showed that the relative abundance of dominant species of soil microorganisms was significantly higher under sufficient water supply and mild water stress treatment than under moderate water stress treament. Under the mild water stress condition, the relative abundance of the most dominant species in each classification level sequentially decreased with the bacterial fertilizer added increasingly. Adding a small amount of bacterial treatment fertilizer to moderate water stress can improve the overall abundance of soil microbial communities during the growth period of new shoots. It was found that Proteobacteria, Bacteroidetes, Gemmatimonadetes, Actinobacteria, Firmicutes, Acidobacteria, Chloroflexi, Planctomycetes, Thaumarchaeota, Verrucomicrobia, and the other bacteria were the major bacterial phyla in the rhizosphere soil of delayed cultivation grapes, among, which Proteobacteria were the most dominant group. Therefore, adding a small amount of bacterial fertilizer under the mild water stress treatment can not only improve the diversity and richness of soil microorganisms during the fruit expansion period, but also significantly save water resources compared with the traditional irrigation regimes.

Amino acids foliar spraying palliate the negative effects of low irrigation on greenhouse sweet Cayenne pepper

AbstractSweet Cayenne pepper is a nutrient‐dense, sweet‐tasting greenhouse vegetable that often faces water stress in dry areas, and optimizing growth with minimum water consumption is crucial. In this study, we investigated the impacts of amino acids (AAs) foliar application on reducing water stress losses in sweet Cayenne pepper cv. “Lombard” under greenhouse conditions. The pepper bushes were irrigated in 3‐day and 6‐day intervals and simultaneously sprayed with an AA fertilizer (0, 150, and 300 mg/L). Vegetative growth, reproductive traits, and yield parameters were measured. Results showed significant decreases in the plant height, the roots length, SPAD, leaf greenness index, and the pepper leaves turn yellow under brief drought stress. The number of flowers was reduced by up to 50%, and the 3‐month yield decreased significantly from 7 to 5.05 kg/m2. However, with AAs foliar application, vegetative growth, fruit number, and yield increased significantly. The highest yield, 2.93 kg/plant, was observed in 300 mg/L AAs, while the minimum yield, with an average of 1.83 kg/plant recorded under water stress treatment without AAs application. The spray of AAs fertilizer remarkably improves the yield and quality of pepper fruit and reverses the destructive effects of low irrigation. The future direction could focus on the mechanism of the positive impact of AA foliar application on growth, yield, and quality of the fruit, particularly in water stress conditions, to further optimize growth and minimize water consumption.

How nano‐iron chelate and arbuscular mycorrhizal fungi mitigate water stress in Lallemantia species: A growth and physio‐biochemical properties

AbstractBackgroundWater deficit can seriously affect the growth, yield, and biochemical properties of plants; however, the application of nano‐iron chelate and arbuscular mycorrhizal fertilizers in water deficit has been considered one of the most promising methods to improve plant growth and enhance drought tolerance.AimsThis study aimed to investigate the effects of nano‐iron chelated (nFe) fertilizer and arbuscular mycorrhizal fungi (AMFs) on the growth, yield, root colonization, mycorrhizal dependency, water use efficiency (WUE), physio‐biochemical properties, and seed biochemical properties of Lallemantia iberica and Lallemantia royleana species under drought stress.MethodsA split‐factorial experiment was conducted using a randomized complete block design with three replications. The main plot consisted of three drought stress levels (according to the depletion of soil available water) of 30% (I1; without stress), 60% (I2; mild stress), and 90% (I3; severe stress). The subplots were the factorial combination of fertilizers (F) (without fertilizer, nano‐iron chelate [nFe], and AMFs) and plant species (S) of Lallemantia (L. iberica and L. royleana).ResultsA decrease in the irrigation regime caused a reduction in growth, seed yield, WUE, chlorophyll content, nutrient uptake, seed oil, and mucilage content, as well as an increase in lipid peroxidation and hydrogen peroxide. Compared with nFe, AMF significantly increased root colonization by mycorrhizal fungi in both species across irrigation regimes. Furthermore, AMF inoculation enhanced nutrient uptake, mucilage, oil, and fatty acids by increasing the WUE. Higher mycorrhizal dependency in inoculated plants played an important role in increasing proline and antioxidant activities in the leaves of the host plant. The water stress and fertilization treatments resulted in the highest root colonization, mycorrhizal dependency, proline content, and antioxidant enzyme activities in L. royleana, as well as the highest WUE, accumulation of fatty acids, and nutrient uptake was observed in L. iberica. Interestingly, the mycorrhization potential of Lallemantia sp. is clearly defined.ConclusionsThe results highlighted that AMFs can promote Lallemantia to increase seed mucilage and oil under water stress. Overall, we found that both Lallemantia species responded well to AMF inoculation under water deficit conditions, where nFe was found to be less effective.

Isolation and molecular characterization of an FSK2-type dehydrin from Atriplex halimus

Dehydrins form the group II LEA protein family and are known to play multiple roles in plant stress tolerance and enzyme protection. They harbor a variable number of conserved lysine rich motifs (K-segments) and may also contain three additional conserved motifs (Y-, F- and S-segments). In this work, we report the isolation and characterization of an FSK2-type dehydrin from the halophytic species Atriplex halimus, which we designate as AhDHN1. In silico analysis of the protein sequence revealed that AhDHN1 contains large number of hydrophilic residues, and is predicted to be intrinsically disordered. In addition, it has an FSK2 architecture with one F-segment, one S-segment, and two K-segments. The expression analysis showed that the AhDHN1 transcript is induced by salt and water stress treatments in the leaves of Atriplex seedlings. Moreover, circular dichroism spectrum performed on recombinant AhDHN1 showed that the dehydrin lacks any secondary structure, confirming its intrinsic disorder nature. However, there is a gain of α-helicity in the presence of membrane-like SDS micelles. In vitro assays revealed that AhDHN1 is able to effectively protect enzymatic activity of the lactate dehydrogenase against cold, heat and dehydration stresses. Our findings strongly suggest that AhDHN1 can be involved in the adaptation mechanisms of halophytes to adverse environments.

Assessment of UAV thermal imagery to monitor water stress in olive trees

Assessment of UAV thermal imagery to monitor water stress in olive trees

The Role of Regular and Nano-Chitosan in some Indicators of Vegetative and Root Growth of Tecoma stans (L.) Seedlings Under Different Levels of Water Stress

A factorial experiment was conducted with three factors, the first using three levels of water stress (50, 75 and 100%) of the field capacity value, the second spraying seedlings of Tecoma stans (L.) Juss. ex Kunth with regular chitosan in three concentrations (0, 150 and 300 mg.L-1), and the third spraying seedlingsat with nano-chitosan in three concentrations (0 and 150 and 300 mg.L-1). arithmetic mean of the coefficients was compared. Statistically according to Duncan’s Multiple Range Test. The results of the single effect of water stress showed the superiority of the seedlings that were treated with light water stress treatment by (100%) of the field capacity value, as well as the single effect of the regular and nano-chitosan biofertilizer, the superiority of the seedlings that were treated with a concentration of (300 mg.L-1) in the increase in the height of the seedlings, the increase in the diameter of the main stem of the seedling, main root length and root volume in the increase in the height of the seedlings, the increase in the diameter of the main stem of the seedling, main root length and root volume.

The North American Monsoon buffers forests against the ongoing megadrought in the Southwestern United States.

The US Southwest has been entrenched in a two-decade-long megadrought (MD), the most severe since 800 CE, which threatens the long-term vitality and persistence of regional montane forests. Here, we report that in the face of record low winter precipitation and increasing atmospheric aridity, seasonal activity of the North American Monsoon (NAM) climate system brings sufficient precipitation during the height of the summer to alleviate extreme tree water stress. We studied seasonally resolved, tree-ring stable carbon isotope ratios across a 57-year time series (1960-2017) in 17 Ponderosa pine forests distributed across the NAM geographic domain. Our study focused on the isotope dynamics of latewood (LW), which is produced in association with NAM rains. During the MD, populations growing within the core region of the NAM operated at lower intrinsic and higher evaporative water-use efficiencies (WUEi and WUEE , respectively), compared to populations growing in the periphery of the NAM domain, indicating less physiological water stress in those populations with access to NAM moisture. The disparities in water-use efficiencies in periphery populations are due to a higher atmospheric vapor pressure deficit (VPD) and reduced access to summer soil moisture. The buffering advantage of the NAM, however, is weakening. We observed that since the MD, the relationship between WUEi and WUEE in forests within the core NAM domain is shifting toward a drought response similar to forests on the periphery of the NAM. After correcting for past increases in the atmospheric CO2 concentration, we were able to isolate the LW time-series responses to climate alone. This showed that the shift in the relation between WUEi and WUEE was driven by the extreme increases in MD-associated VPD, with little advantageous influence on stomatal conductance from increases in atmospheric CO2 concentration.

Impact of shading on evapotranspiration and water stress of urban trees

AbstractEvapotranspiration of urban street trees is essential in mitigating urban heat islands due to its cooling effect. However, current shifts in rainfall and temperature regimes towards drier and hotter periods in Central Europe have caused substantial water stress for street trees. Quantifying and subsequently managing these changing dynamics as well as estimating evapotranspiration and water availability is necessary but at the same time extremely challenging in urban environments. Both dynamics are influenced by soil sealing and complex shading patterns of the surrounding street canyon, which vary on a small spatial scale as a function of the canyon layout and orientation. In the present study, the diurnal patterns of six typical urban shading types for street trees were derived by considering a large set of street orientations, widths and tree positions within the street canyon. A shading model was integrated into a hydrological urban tree model to assess the impact of those shading types on diurnal patterns of radiation and evapotranspiration rates calculated using the Penman–Monteith approach and the resulting soil moisture conditions for several vegetation seasons and water‐supply scenarios. The modelling results showed that the six shading patterns significantly influenced the simulated hourly, daily and seasonal potential and actual evapotranspiration rates and water availability. Shaded trees have a substantially reduced, simulated water stress period, regardless of initial water supply, and are able to provide a longer‐lasting cooling function during dry periods due to higher evapotranspiration rates later in the summer season.

Water Stress Affected Seed Accumulation of Non-reducing Soluble Sugars and Germination Performance of Three Chickpea Cultivars

Background: Water stress may alter the seed chemical composition and cause changes in the concentrations of non reducing soluble sugars in seeds and germination performance of chickpea. We evaluated the effect of water stress during chickpea seed development on seed (i) accumulation of non-reducing soluble sugars, and (ii) vigour and germination. Methods: Three chickpea cultivars (Desi-K, Saina-K and ICCV-K) were subjected to two water regimes (water stress- withholding irrigation after flowering and non-stressed- irrigation at 3-day intervals throughout the crop growth) in a completely randomized design with three replications. Seed size, viability, sugars content, solute leakage, germination percentage and mean germination time were determined from seeds harvested at physiological maturity. Result: Water stress increased the raffinose seed content of Saina-K and Desi-K, decreased the raffinose seed content in ICCV-K, but had no effect on sucrose and stachyose content. Electrical conductivity (EC) increased with water stress in all cultivars, but the increase was greater in ICCV-K (57%) compared to Desi-K (18%) and Saina-K (12%). Non-stressed seeds had larger seed size, higher seed viability and germination percentage and lower EC and mean germination time than stressed seeds. Clearly, sufficient water at seed development stage is crucial for productivity of subsequent crops as it affects seed quality. However, we recommend further studies using a wide range of water stress treatments and chickpea cultivars with different seed size, seed color and seed coat texture.

Photo-oxidative stress leading to oxylipin accumulation may trigger drought-induced leaf abscission in olive trees.

Olive trees shed their leaves under severe drought as a defence mechanism. Foliar drought-induced abscission is a programmed process occurring in a differentiated cell layer at the base of the petiole. Considering the antioxidant properties of vitamin E and its interplay with lipid peroxidation-derived jasmonates in abiotic stress responses, we hypothesized about their possible role in abscission signaling by forming a jasmonates-increasing basipetal gradient along the leaf up to the abscission zone. We exposed young olives trees to water withdrawal for 21 days, after which five leaf sections, from the apex to the petiole, were sampled on both attached and detached leaves of irrigated and water-stressed trees. We found that prolonged drought stress resulted in a sharp reduction in the photosystem II efficiency, chlorophyll and vitamin E contents in leaves, leading to photo-oxidative stress, reflected by the increase in lipid peroxidation. In addition, the content of chloroplast-derived oxylipins and phytohormones, such as jasmonoyl-isoleucine and salicylic acid, increased. At the same time, α-tocopherol decreased in the petiole of water-stressed attached leaves, suggesting a conditioning for the abscission process to occur. Although no differences were observed in petioles from attached and detached leaves, the dropped ones showed higher oxidative stress in the leaf blade. It is concluded that redox signaling through oxylipins accumulation may trigger leaf abscission in drought-stressed olive trees. Mechanical stress is, however, additionally needed to execute leaf abscission once the abscission zone is properly conditioned. This article is protected by copyright. All rights reserved.

Effects of water stress on starch synthesis and accumulation of two rice cultivars at different growth stages.

Rice is a water intensive crop and soil water conditions affect rice yield and quality. However, there is limited research on the starch synthesis and accumulation of rice under different soil water conditions at different growth stages. Thus, a pot experiment was conducted to explore the effects of IR72 (indica) and Nanjing (NJ) 9108 (japonica) rice cultivars under flood-irrigated treatment (CK, 0 kPa), light water stress treatment (L, -20 ± 5 kPa), moderate water stress treatment (M, -40 ± 5 kPa) and severe water stress treatment (S, -60 ± 5 kPa) on the starch synthesis and accumulation and rice yield at booting stage (T1), flowering stage (T2) and filling stage (T3), respectively. Under LT treatment, the total soluble sugar and sucrose contents of both cultivars decreased while the amylose and total starch contents increased. Starch synthesis-related enzyme activities and their peak activities at mid-late growth stage increased as well. However, applying MT and ST treatments produced the opposite effects. The 1000-grain weight of both cultivars increased under LT treatment while the seed setting rate increased only under LT3 treatment. Compared with CK, water stress at booting stage decreased grain yield. The principal component analysis (PCA) showed that LT3 got the highest comprehensive score while ST1 got lowest for both cultivars. Furthermore, the comprehensive score of both cultivars under the same water stress treatment followed the trend of T3 > T2 > T1, and NJ 9108 had a better drought-resistant ability than IR72. Compared with CK, the grain yield under LT3 increased by 11.59% for IR72 and 16.01% for NJ 9108, respectively. Overall, these results suggested that light water stress at filling stage could be an effective method to enhance starch synthesis-related enzyme activities, promote starch synthesis and accumulation and increase grain yield.

Influence of Silicon on Tolerance to Water Deficit of Peach Trees

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

Effect of Water Deficit on Germination, Growth and Biochemical Responses of Four Potentially Invasive Ornamental Grass Species

Ornamental plant species introduced into new environments can exhibit an invasive potential and adaptability to abiotic stress factors. In this study, the drought stress responses of four potentially invasive ornamental grass species (Cymbopogon citratus, Cortaderia selloana, Pennisetum alopecuroides and P. setaceum) were analysed. Several seed germination parameters were determined under increasing polyethylene glycol (PEG 6000) concentrations. Additionally, plants in the vegetative stage were subjected to intermediate and severe water stress treatments for four weeks. All species registered high germination rates in control conditions (no stress treatment), even at high PEG concentrations, except C. citratus, which did not germinate at -1 MPa osmotic potential. Upon applying the water stress treatments, P. alopecuroides plants showed the highest tolerance, and C. citratus appeared the most susceptible to drought. Stress-induced changes in several biochemical markers (photosynthetic pigments, osmolytes, antioxidant compounds, root and shoot Na+ and K+ contents), highlighted different responses depending on the species and the stress treatments. Basically, drought tolerance seems to depend to a large extent on the active transport of Na+ and K+ cations to the aerial part of the plants, contributing to osmotic adjustment in all four species and, in the case of the most tolerant P. alopecuroides, on the increasing root K+ concentration under water deficit conditions. The study shows the invasive potential of all species, except C. citratus, in dry areas such as the Mediterranean region, especially in the current climate change scenario. Particular attention should be given to P. alopecuroides, which is widely commercialised in Europe as ornamental.