Decrease In Transpiration Rate Research Articles

Metabolome profiling reveals impact of water limitation on grain filling in contrasting rice genotypes

Drought significantly decreases crop productivity, especially in high water consuming crops like rice. Grain filling is one of the important critical growth phases in rice and drought during this phase leads to significant reduction in yield. In this study, a comparison was made between IR64 (drought susceptible) and Apo (drought tolerant) rice genotypes to capture the response to water limitation (50% field capacity (FC)) compared with the control (100%FC) during grain filling. Plants were grown in a high-throughput phenomics facility for precise imposition of moisture stress during grain filling. Apo performed better in water limited conditions with lower reduction of photosynthetic rate and maintenance of lower leaf temperature than IR64. Days from sowing to maturity, spikelet fertility and seed weight were more impeded by water limitation in IR64 than in Apo. Unlike Apo, IR64 did not show any decrease in transpiration rate at 50%FC compared with 100%FC. Metabolomic profiling of spikelets at grain filling showed distinct effects of water limitation on accumulation of metabolites, especially in Apo. Secondary metabolism, mainly the phenylpropanoid pathway involved in scavenging mechanisms, was upregulated in Apo. Accumulation of most amino acids was significantly higher in IR64 than in Apo. Due to higher rates of photosynthesis under stress, most carbohydrates accumulated more in Apo than in IR64 at 50%FC. Sucrose transporters were significantly upregulated in water limited conditions especially in Apo. Overall, thanks to higher source capacity, more source to sink transport and better scavenging, Apo showed a lower reduction in yield than IR64.

The Regulatory Role of Silicon in Mitigating Plant Nutritional Stresses.

It has been long recognized that silicon (Si) plays important roles in plant productivity by improving mineral nutrition deficiencies. Despite the fact that Si is considered as ‘quasi–essential’, the positive effect of Si has mostly been described in resistance to biotic and tolerance to abiotic stresses. During the last decade, much effort has been aimed at linking the positive effects of Si under nutrient deficiency or heavy metal toxicity (HM). These studies highlight the positive effect of Si on biomass production, by maintaining photosynthetic machinery, decreasing transpiration rate and stomatal conductance, and regulating uptake and root to shoot translocation of nutrients as well as reducing oxidative stress. The mechanisms of these inputs and the processes driving the alterations in plant adaptation to nutritional stress are, however, largely unknown. In this review, we focus on the interaction of Si and macronutrient (MaN) deficiencies or micro-nutrient (MiN) deficiency, summarizing the current knowledge in numerous research fields that can improve our understanding of the mechanisms underpinning this cross-talk. To this end, we discuss the gap in Si nutrition and propose a working model to explain the responses of individual MaN or MiN disorders and their mutual responses to Si supplementation.

Abscisic Acid and Sulfate Offer a Possible Explanation for Differences in Physiological Drought Response of Two Maize Near-Isolines.

The hypothesis was tested that differences in response to water-deficits between low osmotic potential (LOP) and high osmotic potential (HOP) maize (Zea mays L.) near-isolines were associated with differences in transpiration rate sensitivity to abscisic acid (ABA) and/or sulfate. In a series of four experiments, decreases in transpiration rate (DTR) of whole plants and fully expanded leaves were measured in response to treatments of 1.0 µM ABA and 15 mM MgSO4 singly and in combination following long (2 day) and short (180 min) exposures. There was little evidence that intact plants grown on soil were responsive to the treatments. For hydroponically grown plants subjected to long exposure, there was similarly no response to treatments. Further, the short exposure of hydroponically grown plants to solely ABA or a combination of chemicals resulted in no sensitivity in DTR for either of the near-isolines. On the other hand, when these plants were fed sulfate, the transpiration was stimulated by about 20% for the LOP and 60% for the HOP. Detached leaves proved to be the most sensitive to treatment. Treatment with the two chemicals singly caused essentially equivalent DTR in the two near-isolines. However, treatment with ABA plus sulfate resulted in different DTR between the two near-isolines with values of 65% for the LOP and 16% for the HOP near-isoline. Overall, these results showed that the short exposure treatment of hydroponically grown plants or detached leaves supported the hypothesis of different transpiration rate sensitivities of the near-isolines in response to ABA and sulfate treatments.

Microsphere stem blockage as a screen for nitrogen-fixation drought tolerance in soybean.

Symbiotic nitrogen-fixation of soybean (Glycine max [Merr.] L) commonly decreases in response to soil drying in advance of other plant processes. While a few soybean lines express nitrogen-fixation drought tolerance, breeding for genetic variation is hampered by laborious phenotyping procedures. The objective of this research was to explore the potential of an initial screen for nitrogen-fixation drought-tolerant genotypes based on a possible relationship with xylem-vessel diameter. The hypothesis was that nitrogen-fixation drought tolerance might result from fewer, large-diameter xylem vessels in the stem that are vulnerable to disrupted flow as water deficit develops. The disrupted flow could cause nitrogen products to accumulate in nodules resulting in negative feedback on nitrogen-fixation rate. The proposed screen involved exposing de-rooted shoots to a suspension containing microspheres (45-53 μm diameter) and recording the decrease in transpiration rate as a result of microsphere xylem-blockage. Two soybean populations were tested. One population was progeny derived from mating of two parents with high and low nitrogen-fixation drought sensitivity. A high correlation (R2 =0.68; P < 0.001) was found in this population between decreasing transpiration rate resulting from the microsphere treatment and increasing sensitivity of nitrogen-fixation to soil drying. The second tested population consisted of 16 genotypes, most of which had been previously identified in germplasm screens as expressing nitrogen-fixation drought tolerance. Nearly half of the lines in this second population were identified in the screen as showing minimum blockage of transpiration when exposed to the microspheres. Overall, these results showed the potential of using the microsphere screen to identify candidate genotypes expressing nitrogen-fixation drought tolerance.

Morphophysiological changes by mepiquat chloride application in Eucalyptus clones

First study of mepiquat chloride as a growth regulator in Eucalyptus. Application of mepiquat chloride in Eucalyptus clones at planting may promote drought resistance. The reduction of available areas has pushed Eucalyptus away to marginal areas with low water availability. Management practices such as the application of growth retardants may have potential to modify plant morphological and physiological features, increasing their drought tolerance. Trying to understand the drought tolerance mechanisms of Eucalyptus clones, the objective of this work was to evaluate the effects of different mepiquat chloride (MC) concentrations to Eucalyptus clones on morphological and physiological changes. Commercial clones of E. grandis × E. urophylla hybrid were planted in 20 L pots in a complete randomized block design with eight replications and four treatments. The treatments consisted of three concentrations of MC: 250, 500 and 1000 mg L−1 of MC. The control treatment consisted of a non-MC application (0 mg L−1 of MC). Evaluations of morphological and physiological parameters were carried out for 35 days after the MC application. Results indicated morphophysiological changes after the MC application. Eucalyptus clones increased root dry mass (RDM), total dry mass (TDM), number of leaves and secondary branches, and decreased height. MC application modified the physiological plant system improving intrinsic water use efficiency (WUEi) and SPAD index, and decreasing transpiration rates (E) and stomatal conductance (gs). RDM, TDM, E, WUEi and SPAD index improved when 250 and 500 mg L−1 MC concentration were applied. Our results suggest that MC application may promote drought resistance to Eucalyptus clones.

GDSL lipase occluded stomatal pore 1 is required for wax biosynthesis and stomatal cuticular ledge formation.

The plant leaf surface is coated with a waterproof cuticle layer. Cuticle facing the stomatal pore surface needs to be sculpted to form outer cuticular ledge (OCL) after stomatal maturation for efficient gas exchange. Here, we characterized the roles of Arabidopsis GDSL lipase, Occlusion of Stomatal Pore 1 (OSP1), in wax biosynthesis and stomatal OCL formation. OSP1 mutation results in significant reduction in leaf wax synthesis and occlusion of stomata, leading to increased epidermal permeability, decreased transpiration rate, and enhanced drought tolerance. We demonstrated that OSP1 activity is critical for its role in wax biosynthesis and stomatal function. In vitro enzymatic assays demonstrated that OSP1 possesses thioesterase activity, particularly on C22:0 and C26:0 acyl-CoAs. Genetic interaction analyses with CER1 (ECERIFERUM 1), CER3 (ECERIFERUM 3) and MAH1 (Mid-chain Alkane Hydroxylase 1) in wax biosynthesis and stomatal OCL formation showed that OSP1 may act upstream of CER3 in wax biosynthesis, and implicate that wax composition percentage changes and keeping ketones in a lower level play roles, at least partially, in forming stomatal ledges. Our findings provided insights into the molecular mechanism mediating wax biosynthesis and highlighted the link between wax biosynthesis and the process of stomatal OCL formation.

The influence of application of biochar and metal-tolerant bacteria in polluted soil on morpho-physiological and anatomical parameters of spring barley.

The paper presents the results of the model experiment on spring barley (Hordeum vulgare L.) grown in polluted soil. The influence of separate and combined application of wood biochar and heavy metal-tolerant bacteria on morpho-physiological, anatomical and ultrastructural parameters of H. vulgare L. has been studied. The joint application of biochar and bacteria increased the shoot length by 2.1-fold, root length by 1.7-fold, leaf length by 2.3-fold and dry weight by threefold compared to polluted variant, bringing the plant parameters to the control level. The maximal quantum yield of photosystem II decreased by 8.3% in H. vulgare L. grown in contaminated soil, whereas this decrease was less in biochar (7%), bacteria (6%) and in combined application of bacteria and biochar (5%). As for the transpiration rate, the H. vulgare L. grown in polluted soil has shown a decrease in transpiration rate by 26%. At the same time, the simultaneous application of biochar and bacteria has led to a significant improvement in the transpiration rate (14%). The H. vulgare L. also showed anatomical (integrity of epidermal, vascular bundles, parenchymal and chlorenchymal cells) and ultrastructural (chloroplasts, thylakoid system, plastoglobules, starch grains, mitochondria, peroxisomes, ribosomes, endoplasmic reticulum, vacuoles) changes, revealed by light-optical and transmission electron microscopy of leaf sections. The effects were most prominent in H. vulgare L., grown in polluted soil but gradually improved with application of biochar, bacteria and their combination. The use of biochar in combination with metal-tolerant bacteria is an efficient tool for remediation of soils, contaminated with heavy metals. The positive changes caused by the treatment can be consistently traced at all levels of plant organization.

Interactive Effects of the CO2 Enrichment and Nitrogen Supply on the Biomass Accumulation, Gas Exchange Properties, and Mineral Elements Concentrations in Cucumber Plants at Different Growth Stages

The concentration changes of mineral elements in plants at different CO2 concentrations ([CO2]) and nitrogen (N) supplies and the mechanisms which control such changes are not clear. Hydroponic trials on cucumber plants with three [CO2] (400, 625, and 1200 μmol mol−1) and five N supply levels (2, 4, 7, 14, and 21 mmol L−1) were conducted. When plants were in high N supply, the increase in total biomass by elevated [CO2] was 51.7% and 70.1% at the seedling and initial fruiting stages, respectively. An increase in net photosynthetic rate (Pn) by more than 60%, a decrease in stomatal conductance (Gs) by 21.2–27.7%, and a decrease in transpiration rate (Tr) by 22.9–31.9% under elevated [CO2] were also observed. High N supplies could further improve the Pn and offset the decrease of Gs and Tr by elevated [CO2]. According to the mineral concentrations and the correlation results, we concluded the main factors affecting these changes. The dilution effect was the main factor driving the reduction of all mineral elements, whereas Tr also had a great impact on the decrease of [N], [K], [Ca], and [Mg] except [P]. In addition, the demand changes of N, Ca, and Mg influenced the corresponding element concentrations in cucumber plants.

Impact of Elevated CO2 on Two Successive Generations of CO2 Responsive Maize Genotype

A CO2-responsive maize (Zea mays L.) genotype, Harsha, was selected to assess its response to elevated CO2 in successive generation. The selfed seeds harvested from elevated CO2 (eCO2) raised maize plants were sown in open-top chambers (OTCs) to raise second generation (H-II) plants along with fresh seeds as first generation (H-I) under both ambient (400 ppm) and elevated (550 ppm) CO2 (eCO2) conditions. It was observed that second-generation (H-II) plants also showed improved performance under eCO2 for morphological and physiological parameters. It is pertinent to mention that the H-II plants were more vigorous even under ambient CO2 (aCO2) condition as compared to H-I plants. The vigor of H-II plants was higher for majority of the morphological and biomass parameters under both aCO2 and eCO2. In H-II, the increased photosynthetic rate (Anet) was 6% and decrease in transpiration rate (Tr) was 49%, which resulted in significant increase (110%) in water use efficiency. This reveals that the elevated CO2 improved the physiological performance of the maize plant over the generations. These results clearly elucidate that a C4 crop like maize can respond to elevated CO2 and higher response in subsequent generations may favor the crop resilience under changed climatic conditions.

Yield-related phenotypic traits of drought resistant maize genotypes

The aim of this study was to evaluate two maize genotypes with contrasting drought-resistant phenotypic traits and to characterize how the plastic phenotypic traits contribute to yield potential under drought. The maize genotypes DKB 390 and BRS 1010 present contrasting yield traits in relation to drought and were treated with two water regimes: well-watered plant (WW, ≈−2 kPa) and water deficit (WD, ≈−100 kPa). In WD conditions, DKB 390 had a greater capacity to accumulate biomass in shoots than BRS 1010, indicating that shoot traits are important in increasing yield gain in the DKB 390 drought tolerant genotype and therefore, an important phenotypic trait for breeding for high yield in drought conditions. However, neither the total root dry mass nor its ratio to the shoot was related to increased yield. A large reduction in gas exchange and increased water use efficiency was observed in BRS 1010 compared to DKB 390. These traits are likely related to yield loss mainly due to decreased transpiration rate and stomatal conductance, which led to low photosynthetic rates and reduced growth. The root angle between genotypes was a constitutive trait and can be primarily responsible for the differences in yield. However, this trait in the DKB 390 genotype was affected by WD, as indicated by narrowing of the root angle. Our work describes the relationship between the narrow root growth angle in DKB 390 and its association with an increased capacity for water uptake in deeper regions, which may result in higher yield under drought. Regarding leaf anatomy we hypothesized that both osmotic adjustment and cell wall properties can influence anisotropic cell expansion under WD conditions and result in leaf tissue with higher yield potential in DKB 390. The high plasticity of vascular tissues and wide vessels could indicate a greater propensity for embolism and a slower response to WD, leading to yield loss in BRS 1010. The results of the phenotypic plasticity of maize genotypes show a negative relationship between high plasticity and yield potential and suggest that high plasticity can result in higher yield potential only when are present in phenotypic traits responsible for higher water uptake and drought tolerance.

Unraveling the genetic architecture for carbon and nitrogen related traits and leaf hydraulic conductance in soybean using genome-wide association analyses

BackgroundDrought stress is a major limiting factor of soybean [Glycine max (L.) Merr.] production around the world. Soybean plants can ameliorate this stress with improved water-saving, sustained N2 fixation during water deficits, and/or limited leaf hydraulic conductance. In this study, carbon isotope composition (δ13C), which can relate to variation in water-saving capability, was measured. Additionally, nitrogen isotope composition (δ15N) and nitrogen concentration that relate to nitrogen fixation were evaluated. Decrease in transpiration rate (DTR) of de-rooted soybean shoots in a silver nitrate (AgNO3) solution compared to deionized water under high vapor pressure deficit (VPD) conditions was used as a surrogate measurement for limited leaf hydraulic conductance. A panel of over 200 genetically diverse soybean accessions genotyped with the SoySNP50K iSelect BeadChips was evaluated for the carbon and nitrogen related traits in two field environments (Athens, GA in 2015 and 2016) and for transpiration response to AgNO3 in a growth chamber. A multiple loci linear mixed model was implemented in FarmCPU to perform genome-wide association analyses for these traits.ResultsThirty two, 23, 26, and nine loci for δ13C, δ15N, nitrogen concentration, and transpiration response to AgNO3, respectively, were significantly associated with these traits. Candidate genes that relate to drought stress tolerance enhancement or response were identified near certain loci that could be targets for improving and understanding these traits. Soybean accessions with favorable breeding values were also identified. Low correlations were observed between many of the traits and the genetic loci associated with each trait were largely unique, indicating that these drought tolerance related traits are governed by different genetic loci.ConclusionsThe genomic regions and germplasm identified in this study can be used by breeders to understand the genetic architecture for these traits and to improve soybean drought tolerance. Phenotyping resources needed, trait heritability, and relationship to the target environment should be considered before deciding which of these traits to ultimately employ in a specific breeding program. Potential marker-assisted selection efforts could focus on loci which explain the greatest amount of phenotypic variation for each trait, but may be challenging due to the quantitative nature of these traits.

Study on the Effect of Prawn (Machrobrachuim rosenbergii) Chitosan Coating on Peeled Shallot (Allium ascalonicum)

Shallot (Allium ascalonicum) is the most important commercial vegetable crop grown in India. Shallot peeling is tough and consumes time. The availability of peeled shallots in markets will reduce the time consumed on peeling shallots for cooking. But peeled shallot does not have longer shelf life. Edible coating for peeled shallots can reduce spoilage and can inhibit microbial growth too. The Chitosan coating of shallots was based on the dipping method of coating fruits and vegetables. The study on coating chitosan in shallots and different parameters with varying composition were analyzed. The physio-chemical parameters like protein content, carbohydrate content, calcium content and total phenols content and weight loss shows that there is a significant difference with coated and uncoated Shallot stored at 4C for a period of 15 days. The microbial studies and physical characteristic studies show that number of microbes and decay is significantly less for coated onion samples compared with uncoated samples respectively. The inhibitory effect of chitosan produced from prawn shell against fungi was studied by adding 0.2% oregano oil, 0.4% of Tween 80 (polysorbate 80) and 0.7% of Glycerol. The Zone of inhibition was obtained has which were found to be 3.1cm, 1.5cm and 2.9cm for Oregano (Or), Thyme (Th) and Mint (M) leaves. Addition of 0.1% Tween 80 to 1.5 % chitosan in acetic acid solution improved the effectiveness of coating on the Shallot skin. The above study revealed that Chitosan coatings were in effect on successful quality improvement and extending shelf life of Shallot by delayed ripening, lowered respiration rate, regulated gas exchange, decrease in transpiration rate, retaining fruit firmness, reduction in weight loss etc.

Potato response to silicone compounds (micro and nanoparticles) and potassium as affected by salinity stress

Salinity of irrigation water is an important limitation factor in crop production such as potato worldwide. Foliar application of anti-stress compounds containing mineral nutrients is one of the possible solutions for salinity mitigation. In this field experiment the effects of silicone compounds on potato (cv. Agria) performance was studied as a split plot based on randomised complete block design with three replications at Ferdowsi University of Mashhad, Iran, during 2016 cropping season. Treatments included irrigation salinity [0.3 (non-stress), 5, 8 and 12 dS.m–1] and foliar application of potassium sulphate (1000 ppm), sodium silicate nanoparticles (400 ppm) and silica (1000 ppm). Results indicated that salinity decreased transpiration rate, stomatal conductance, quantum yield of PSΙΙ, membrane stability index, carotenoids, tuber number per plant and tuber yield while it improved water use efficiency and tuber dry matter percentage. Foliar application of anti-stress compounds positively affected quantum yield of PSΙΙ, carotenoids content, DPPH radical scavenging activity, tuber number per plant, tuber yield and tuber dry matter percentage. Although, application of all compounds improved most biochemical and photosynthetic traits, but ameliorative effect of the two silicon compounds, especially sodium silicate nanoparticles was more evident. It seems that silicon application could be an effective strategy in reducing salinity effects and its efficiency will be increased when is used as nanoparticles.

Association of SSR Markers with Cold Tolerance Traits in Diverse Bermudagrass [Cynodon dactylon (L.) Pers.] Accessions

Bermudagrass [Cynodon dactylon (L.) Pers.] is a perennial and typical warm-season grass. It undergoes withering and severe damage under cold stress; thus, cold is considered as a key factor that restricts the widespread use in bermudagrass. Identification of association between molecular markers and cold tolerance-related traits would facilitate the efficient selection of cold tolerant bermudagrass cultivars. A total of 106 diverse bermudagrass accessions, including 4 commercial cultivars and 102 wild germplasms, were tested for cold tolerance and analyzed by 104 simple sequence repeat (SSR) markers. Cold significantly decreased transpiration rate, growth rate and turf quality. There were significant variations in these trait values among the accessions under cold conditions. Two subpopulations were detected in the panel of accessions based on the analysis of 1474 alleles with 104 SSR markers. Clustering analysis revealed that the genetic relationship was affected by the natural habitats. Thirty-four SSR markers were identified to be associated with two or three traits based on the corrected P values (P < 3.5 × 10−4). These markers can be used for genetic improvement of cold tolerance of bermudagrass after further validation.

Wheat drought-tolerance to enhance food security in Tunisia, birthplace of the Arab Spring

Abstract The beginning of the ‘Arab Spring’ in 2011, a regional revolution which started in the Tunisian city of Sidi Bouzid in late 2010, occurred in part as a result of drought-triggered high wheat prices, which in the past led to ‘bread riots’ across several Middle East and North Africa (MENA) nations. Here we present, for the first time, an analysis of possible amelioration of wheat yield loss and greater stability in bread supply resulting from the incorporation of putative drought-tolerant traits into wheat cultivars grown in Tunisia. To this end, we used a simulation crop modeling approach using SSM-Wheat to evaluate yield loss or gain resulting from three types of water-saving traits that have been recently identified in wheat. These consisted in partial stomatal closure at high soil water content, overall decrease in transpiration rate (TR), and partial stomatal closure under elevated vapor pressure deficit (VPD). To capture large gradients in seasonal precipitation across wheat growing areas over a small country such as Tunisia, a grid pattern of 29 × 29 km was established as a basis for the geospatial simulation. Surprisingly, the simulation reflected opposite strategies in terms of water use (water-saving vs aggressive water use). The highest yield gain (30%) resulting from water-saving modification was found to occur in the food-insecure region of Sidi Bouzid. Traits enabling aggressive water use were found to be generally favorable across Tunisia, with one trait leading to up to 80% and 40% increases in yield and its stability in the food-challenged south of the country. However, major yield penalties were found to occur if water-saving traits were to be deployed in the ‘wrong’ region. Those findings could be used as a blueprint to navigate complex trait × environment interactions and to better inform local breeding and management programs to improve wheat yield and it stability in Tunisia and the MENA region in general.

Making Crops Climate Ready

Making Crops Climate Ready

Several Physiological Changes of Cocoa (Theobroma cacao L.) in Response to Vascular Streak Dieback Diseases

The physiological response of cocoa plants under VSD infections is still limited because there is no method in artificial inoculation since Oncobasidium theobromae was reported as parasitic obligates. The investigation of correlation between cocoa responses and VSD attack becomes important information to figure out the effect of decreased productivity as the consequences of the physiological damages. The objective of this research was to describe the pathogen infection and the symptom of VSD through fungal staining method and to asses the changes of some physiological aspects (chlorophyll and gass exchange character) under VSD pathogen infection. This study was conducted in Kaliwining experimental station, ICCRI, Jember, East Java, Indonesia. The result of the study indicated that late infection stage caused chlorophyll degradation, decreasing transpiration rate, and increasing temperature in both tolerant clone (Scavina 6) and susceptible clone (TSH 858). The rate of photosynthesis, stomatal conductance, and concentration of CO 2 in susceptible clone (TSH 858) showed a drastic decrease when infected by VSD pathogen than that of in healthy plants. In resistant clone (Scavina 6), photosynthesis rate, stomatal conductance, and concentration of CO 2 showed no significant decrease when infected by VSD pathogen compared to that non-infected condition.

Improvement in photosynthesis, seed yield and protein content of common bean (Phaseolus vulgaris) by foliar application of 24-epibrassinolide under drought stress

Brassinosteroids (BRs), as a class of plant growth regulators, have been shown to affect different physiological traits of plants and counteract various stresses. We studied the possibility of increasing seed and protein yields of two genotypes of common bean (Phaseolus vulgaris L.) with the exogenous application of 24-epibrassinolide (EBL) in an experiment conducted during 2016 and 2017. Two levels of irrigation (optimal and drought stress) were applied to the main plots, and two genotypes of common bean (cv. Kusha and genotype COS16) and four concentrations of EBL (0, 2, 4 and 6 μm) were allocated to subplots in a factorial arrangement. At the flowering stage, drought stress was applied and bean plants were sprayed with EBL. The results indicate that drought stress reduced leaf area, yield components, seed yield and protein content. Moreover, substantial increase in intercellular CO2 concentration and decrease in transpiration rate, stomatal conductance and net photosynthetic rate were also recorded. However, exogenous application of EBL remarkably improved gas exchange attributes, leaf area, yield components, seed yield and protein content both under optimal irrigation and drought-stress conditions. Analysis of regression showed that, under both water-supply conditions, genotype COS16 would have highest seed yield when receiving 4.05 and 4.52 µm EBL, and cv. Kusha would have the highest seed yield by receiving 3.27 and 3.62 µm EBL. Therefore, EBL can be used as a plant growth regulator to enhance drought tolerance and minimise yield loss of common bean caused by water deficits.

Identification of Virginia‐Type Peanut Genotypes for Water‐Deficit Conditions Based on Early Decrease in Transpiration Rate with Soil Drying

Early decrease in transpiration rate as soil progressively dries allows soil water conservation for sustained crop physiological activity as water deficit continues to increase. This trait is likely to be particularly useful for peanut (Arachis hypogaea L.), which is often grown on sandy soil where water deficit can develop quickly. This study was undertaken to identify peanut genotypes that express this water conservation trait and to determine if it confers a yield advantage. Three approaches were taken. (i) Two populations of peanut were tested in controlled environments during progressive soil drying. Especially high thresholds of soil water content for initiation of decrease in transpiration rate were identified in three lines in each of the breeding populations. (ii) Nine genotypes were identified for field observation of leaf wilting under rain shelters and in the open field. There was a correspondence between the early decrease in transpiration rate with soil drying and delayed wilting. (iii) Yield trial data for three genotypes were examined to identify those lines that consistently had higher yields than the commercial check cultivar ‘Bailey’, particularly at low yield levels commonly associated with drier conditions. When expressing total seed yield in monetary return, these breeding lines had yield values that were consistently superior to Bailey below the US$2000 ha−1 threshold. Based on the three experimental approaches, N12006ol consistently expressed a desired response of early decrease in transpiration rate with soil drying, delayed wilting in the field when soil water deficit developed, and greater yield value than Bailey in low‐yield environments.

Effect of Silicon on Growth and Development of Strawberry under Water Deficit Conditions

Water stress is a major factor that limits agricultural crop production. Silicon (Si) is generally considered as a beneficial element for the growth of higher plants, especially for those grown under stressful environment. This study was conducted to examine the effects of Si on growth and development of strawberry (Fragaria × ananassa ‘Camarosa’) under water stress conditions. A factorial experiment, in a completely randomized design, was used to investigate the effects of three irrigation levels and four Si treatments consisting of 0, 5, 10, and 15 mmol·L−1 potassium silicate (K2SiO3). The results showed that an increase in the levels of water stress caused a decrease in most of the quantitative characteristics such as specific leaf area, chlorophyll fluorescence, net photosynthesis rate, and stomata conductance; addition of Si significantly increased most of the mentioned factors; water stress increased electrolyte leakage, proline, and water use efficiency (WUE); Si treatment significantly decreased transpiration rate and improved chlorophyll content and WUE. Water stress stimulated mineral nutrient absorption whereas Si application decreased it under water stress. In conclusion, it was found that in most of the investigated factors, 10 mmol·L−1 potassium silicate had the best effect on growth and development of strawberry. Besides, Si application had beneficial effects on strawberry plants and the addition of it could alleviate water stress.