Mathematical model GERMINAN for the analysis of germination test results

Isabgol (Plantago ovata) is an important medicinal plant in world that has more medicinal uses. Germination stage is an importance of growth plant stage that often effective by environmental stress including water and salinity stress. In order to study germination characteristics of Isabgol in water and salinity stress conditions were conducted two laboratories experimental. The two experimental were conducted in completely randomized design with 3 and 4 replications for salinity and water stress respectively. The treatment, for salinity and water stress was six potential (zero, -2, -4, -6, -8 and -10 bar) of NaCl and four potential (zero, -4, -8 and -12 bar) of PEG respectively. Results of two experimental showed that increasing water and salinity stress decreased significantly germination rate, germination percentage, plumule and radicle length (P<0.01). Zero to -8 bar was the best range for seed germination on Isabgol. The results showed that in between total characters, plumule length is more sensitive to water and salinity stress. Seem that seed germination on Isabgol has more tolerance in salinity stress condition than to water stress condition.

The study described in this thesis focuses on the quantitative understanding of water uptake by roots under separate and combined salinity and water stresses. The major difficulty in solving Richards' equation stems from the lack of a sink term function that adequately describes root water uptake. From the existing microscopic and macroscopic sink term functions, the empirical macroscopic approach was chosen because it requires the least number of parameters whose values can readily be determined. All existing reduction functions as well as those newly developed in this study are used in the macroscopic model and tested against experimental data. The experimentally obtained data are used to derive the parameter values needed for the simulation model HYSWASOR. The experiments cover root water uptake by alfalfa under salinity stress, water stress, and combined salinity and water stress. This order is followed with the analysis of the data and the simulation.Under salinity stress , both experimental and simulated results indicate that the well-known linear crop response function can be used as a reduction function. The parameter values available in the literature for different reduction functions cannot provide acceptable agreement with the experimental data. When experimentally derived parameters are used in the simulation model, the agreement becomes much closer, but calibration is still needed. The parameter values obtained by calibration differ slightly from the experiments, because the experimentally derived parameter values are based upon mean soil solution salinity. Both experimental and simulation results indicate that different salinity reduction functions can provide almost the same results if the parameter values are well specified. For practical use the linear reduction function with the least number of parameters appears to be adequate.Under water stress , all existing reduction functions as well as the one developed in this study are tested on the experimental data. Since the trend of the experimental relative transpiration versus mean soil water pressure head is nonlinear, the linear reduction function cannot fit the data. The existing nonlinear reduction functions can fit only half of the data range satisfactorily. The best agreement is obtained with the newly developednonlinear two-threshold reduction function .The parameter values obtained by calibration differ only slightly from those of the experiments. Soil water pressure head heterogeneity over the root zone does not play an important role in water uptake. The roots appear to take up water from the relatively wetter parts of the root zone to compensate for the water deficit in the drier parts. On the first day after irrigation both relative transpiration and relative leaf water head are almost the same for the stressed and non-stressed plants. While the simulated transpiration agrees closely with the experimental data, the main reason for the discrepancy between the simulated and actual water contents appears to be water uptake during the night.Under combined water and salinity stress , the additive and multiplicative reduction functions are first tested against the experimental data and then inserted in the simulation model. A new combination reduction function is introduced that differs conceptually from the additive and multiplicative functions. Both the experimental and simulated results show that the newly proposed model fits the data best, while the worst results are obtained with the simple additive model.

Amaranth (Amaranthus spp.) is a promising vegetable species often grown under semi‐arid conditions prone to both drought and salinity. This study was initiated to evaluate the effects of water and salinity stresses, both individually and in combination, on plant growth/leaf water relations and gas exchange of two amaranth genotypes— Amaranthus tricolor and A. cruentus. Plants were grown in a greenhouse in plastic pots filled with a sand/vermiculite mixture and exposed to 8 days of drought and/or salinity stress, a recovery period of 8 days, followed by a final 2 weeks of stress. The treatments consisted of: (1) unstressed control; (2) 100 mM Nad (salt stress); (3) PEG (polyethylene glycol Mw 6000) iso‐osmotic to 100 mMNaCl (water stress); and (4) 50 mM NaQ + PEG iso‐osmotic to 50 mM NaCl (salt + water stress). Plant growth (leaf, stem, root dry mass, root: shoot ratio, leaf area) were reduced by stress treatments. The reduction in shoot growth was greater in plants subjected to PEG‐induced water stress (41% in A. tricolor and 44% in A. cruentus) than in salinised plants (37% in A. tricolor and 27% in A. cruentus). Leaf water and osmotic potentials were reduced by stress treatments whereas turgor potential was largely maintained. Photosynthetic rate, stomatal conductance, and water loss were reduced by all stress treatments. Photosynthetic water‐use efficiency was increased by stress and was greater in salinised than in water‐stressed plants. Salinised plants and those subjected to salt + water stress had a greater degree of osmotic adjustment, so that plants were able to continue growth for a longer period before drying, compared to water‐stressed plants. Most parameters recovered when the stress treatments were discontinued. However, photosynthesis in salt‐stressed plants did not recover indicating a toxic effect of salt on the photosynthetic apparatus. The combined effect of salt + water stress is less detrimental to plant growth than the sum of individual stresses.

Simulating accumulation of mineral nutrients in crops is useful for scheduling fertigation under ideal conditions, but doing so under saline and water stress would be a double beneficial tool. First, fertilization can be scheduled to fit mineral requirements while crops grow, and, second, fertilizers can be limited to the level determined by the stress condition, thus avoiding additional salinization by fertilizer not used by crops. The model considers crop development in a thermal timescale, in which the total crop period is obtained by integration in time of the thermal response equation. This integral is a constant value for a specific crop and cultivar. Biological age is then defined as a fraction of the current thermal time accumulated at any time to the total thermal time required. Using this relative time, the accumulation of mineral nutrients can be calculated as an allometric equation dependent on thermal time. It also considers crop biomass at any biological age, the total biomass of a crop and other specific parameters of the crop and the mineral nutrient being quantified (Misle J Plant Nutr 36:1327–1343, 2013). Thermal time dependence allows this model to follow daily variations of temperature in order to adjust the forecast of the accumulation of mineral nutrients to thermal variations on growth. The model is then coupled with already published equations for water and saline stress. As these restrictions are added to growth, total biomass will not be the maximum attainable for certain agro-climatic conditions, so that restrictions can be transmitted to the nutrient accumulation forecast (Misle and Garrido Determination of crop nutrient accumulation under water or saline stress through an allometric model, El-Zaiem Press, Cairo, Egypt, 2008). In this chapter we contextualize the problem, describe the theoretical background and analyse field experience from 1998 on crops fertigation, following stages of the model development and discussing growth restrictions imposed by saline and water stress to the nonrestricted forecast.

Abiotic stress conditions cause extensive losses to agricultural production worl dwide (Bray, 2002). Drought and salinity stress can significantly affect plant yield in arid and semi-arid regions and not only. Climatic changes will conduct to severe drought conditions and to aridity of some important regions in Romania. One of the most important strategies which could reduce the influence of drought and salinity on alfalfa (Medicago sativa) production is to breed for increased cultivar tolerance. The present paper reports the reactions of some Romanian alfalfa genotypes to salt and water stress. The aim was to elucidate some physiological and metabolic aspects of those stresses, in order to establish screening criteria to facil itate the development of genotypes with enhanced tolerance to field stress conditions. Seeds of nine alfalfa genotypes were sown in Mitcherlich plots filled with a soilsand mixture. The plant were grown in vegetation house under optimal condition up to just before flowering, when for water stress variant the watering was reduced for 10 days; salt stress was imposed on plants by adding 300 mM NaCl/l and under combined stress the plants were treated with 300 mM NaCl/l one week before reducing watering. The alfalfa yield of all studied genotypes was significantly reduced under water and salt stress while stresses combination caused a reduction on fresh biomass, too. Salt stress significantly decreased biomass by more than 37% while water stress by more than 73%. The effects of salt and water stresses on yields were additive but not equal. Alfalfa responded to drought by decreasing leaves transpiration. Between bi omass accumulation and leaves transpiration under water and salt stress there was a linear relationship (r = 0.76*; r = 0.82*). Under optimal condition the proline content was very small (1.7-5.4 mg proline/g f.w.) but there were obviously higher proline contents under salt stress (156-441 μM proline/g f.w.), water stress (45-68 μM proline/g f.w.) and stress combination (120-330 μM proline/g f.w.). The negative effect of salinity and combined stresses on alfalfa growth could be attributed to osmotic effects. Osmotic stress inhibits water uptake from the soil and requires the plant to use energy and carbohydrates in synthesizing organic solutes to adjust its internal osmotic potential. Yield loss results from closing stomata and from energy and carbohydrates use in osmoregulation. The leaves transpiration and biomass accumulation were correlated, suggesting the use of transpiration as a screening tool for drought and saline tolerance of alfalfa genotypes.

The present study aimed at determining the morphological response of Oenothera biennis L. under water stress and salinity stress. Water deficit and salinity stress are one of the major abiotic stress factors show negative impact on growth, development and yield on different agricultural activities. Thus demands the need of developing water deficit and salt tolerant plant varieties. Oenothera biennis L. is one of the important medicinal plant with several medicinal properties, but information related to morphological response which helps in determining the level of water and salinity stress tolerance in Oenothera biennis L. has not been reported yet. So, the present study is carried out to investigate the effect of water stress and salinity stress under different concentrations i.e. water stress (-0.01 M Pa, -0.03 M Pa, -0.05 M Pa and -0.07 M Pa) and salinity stress (25 mM, 50 mM, 75 mM and 100 mM NaCl) on shoot length, no. of leaves, no. of flowers, no. of nodes, seed yield and root length. At lower water and salinity stress concentrations the Oenothera biennis L. has shown tolerance in terms of morphological features. In overall, Oenothera biennis L. is tolerant to mild water stress and salinity stress.

This study aimed to identify the antioxidant responses of sugarcane (Saccharum spp.) varieties subjected to water and saline stress. Sugarcane seedlings of six different varieties obtained through micropropagation were subjected to either water or saline stress, or a combination of water + saline stress. The study was carried out in May 2012, in a greenhouse at the Universidade Federal Rural de Pernambuco (UFRPE). The experimental design was randomized, with treatments arranged in a 6 × 4 factorial scheme (six varieties and four treatments), and four replicates. Lipid peroxidation, hydrogen peroxide (H2O2) concentrations, and relative water content (RWC) were evaluated. Furthermore, we evaluated the plants’ antioxidative defense systems by measuring the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT). The sugarcane varieties had higher lipid peroxidation and/or higher H2O2 concentrations when subjected to the combined water + saline stress. The antioxidant enzymes responded to the water and saline stress treatments differently depending on the sugarcane variety. However, under combined saline + water stress conditions, the enzymes may have become inactivated, which indicates that the response to the combined water + saline stress was different from the sum of the responses to only water stress or only saline stress. High concentrations of malondialdehyde (MDA) associated with low RWC may be an effective indicator of multiple stress sensitivity in sugarcane varieties. The RB99395 and RB867515 sugarcane varieties responded more efficiently to environmental stress, and maintained their cell water content when subjected to either water or saline stress.

Characterizing the effects of previous water and salinity stresses is critical for the evaluation of plant water status, which, in turn, is essential for understanding soil-plant water relations and optimizing irrigation schemes. Recent research has found that hysteresis of plant response following water stress alone can be described by an exponential function of the stress degree on the previous day. To explore and quantify the effects of hysteresis concerning salinity stress and combined water-salinity stress, a hydroponic experiment and a soil column experiment on winter wheat, and a field experiment on cotton were conducted. Like water stress, previous salinity stress and combined water-salinity stress also resulted in hysteretic effects on root-water-uptake. Leaf stomatal conductance and plant transpiration rate of stressed crops could only recover gradually from a previous stressed status after re-watering. When stress was mild, compensatory recovery was found, while incomplete recovery occurred when stress was severe. Although the recovery process was closely related to stress history and type, a recovery coefficient was quantified universally with an exponential function of the stress extent on the previous day (with a coefficient of determination R2 ≥ 0.60). Consideration of hysteresis for water and salinity stresses with a mathematical model led to significant improvement in the simulation of both relative transpiration rate (R2 = 0.94, root mean squared error RMSE = 0.04, maximal absolute error MAE = 0.12) and soil water content (R2 = 0.90, RMSE = 0.01 cm3 cm–3, MAE = 0.03 cm3 cm–3), especially during the recovery periods severely affected by historical stress. Consideration of hysteresis is expected to benefit regulation of soil water and salinity and thus enhance water use efficiency. However, the mechanisms underlying hysteresis, especially the compensatory recovery mechanisms, still need to be further investigated.

One of the priorities in the management of agricultural inputs, such as water and fertilizers, involves investigating the variations in the crop yields under actual field conditions, subjected to the effects of various simultaneous stresses. The current study is mainly aimed at investigating the simultaneous effects of triple water, salinity, and nitrogen stresses on basil, Mazandaran mass cultivar, and determining its production functions in such situations. The study was conducted at Doshan Tappeh Agricultural Experiment Station with an area of one ha in Tehran, Iran. A factorial experiment was conducted in the form of a randomized complete block design with different irrigation levels as the main treatment. In addition, two sub-treatments, i.e., salinity and fertilization, were conducted in three replications by a water and soil laboratory in 2016 and 2017. The irrigation treatments included full irrigation (FI) in 100% (W1) and deficit irrigation (DI) in 80% (W2), 60% (W3), and 40% (W4) of crop water requirements. The salinity treatment involved 1.175 ds m−1 (S1) (control treatment), 3 ds/m (S2), and 5 ds/m (S3), while the fertilization treatment involved 100% (F1) (control treatment), 75% (F2), and 50% (F3) of the recommended fertilizer requirement. Overall, results indicated that under a constant fertilizer treatment, the rise in the salinity and water stress reduced the basil yield, while under the water-fertilizer double stress, the basil yield rate first decreased and then had a notable increase. By applying water and salinity stresses, the crop yield experienced a steeper reduction under the water stress than the salinity stress. Contrary to expectations, fertilization reduced basil yield under these conditions.

A split-split-plot design with three replications in two years of 2009 and 2010 was conducted to investigate the effect of different levels of irrigation water (main plot), salinity of irrigation water (sub-plot) and nitrogen fertilizer rate (sub-subplot) on maize growth rate and gas exchange. Irrigation treatments were I1 (1.0 crop evapotranspiration (ETc)+0.25ETc as leaching), I2 (0.75I1) and I3 (0.5I1) applied at 7-day intervals. The salinity treatments of irrigation were 0.6 (fresh water), 2.0 and 4.0 dS m -1 . There were also three nitrogen (N) treatments including 0, 150 and 300 kg N ha -1 . Results showed that vegetative growth stage of maize in salinity stress lasted 5% more than that in water stress. The most sensitive trait under water, salinity and nitrogen stress was grain yield (GY). The optimum treatment for maize production is full fresh water application by 150 kg N ha -1 . Results also showed that crop growth rate (CGR) was statistically higher in I1 and I2 as 58 and 34% relative to I3 treatment, respectively. Furthermore, CGR was statistically lower in S2 and S3 as 10 and 18% relative to S1, respectively. Besides, N application significantly increased CGR by an average of 15% as compared with no N rate. The net assimilation rate (NAR) reached its maximum value in I2, S2 and N2 relative to other treatments indicating that NAR did not necessarily occurred at maximum LAI conditions. In general, maize had statistically greater NAR in pollination and filling stages relative to other growth stages. Results of gas exchange for maize as a sensitive crop to water deficit, showed that photosynthesis rate (An) and stomatal conductance (gs) were statistically decreased in water deficit by an average of 30 and 43% as compared to full irrigation treatment, respectively. However, reduction in An and gs in salinity conditions was the same as 13% compared to no salinity treatment. Transpiration rate (T) was statistically lower under water and salinity stress by an average of 75 and 26% as compared to no water and salinity stress, respectively. The ratio of An/gs in I2 and I3 was

The response of alfalfa to water and salinity stress differs during the whole growth period, and water stress has the most severe effects on the yield of alfalfa at the branching stage. However, the presence of soil salt can also enhance its drought resistance and alleviate the impact of water stress on yield. Thus, information on the responses of aboveground biomass, water-use efficiency and osmolytes to water and salinity stress at the branching stages of alfalfa development is urgently required. A pot experiment that combined three irrigation levels of 55–70% (W1), 70–85% (W2) and 85–100% (W3) of field capacity (FC) and four salinity levels was conducted in Dengkou County, Inner Mongolia, China, in 2018 and 2019. The percentage of mixed salt (NaCl:Na2SO4 = 1:1 [w/w]) added for the salinity treatments was 0, 2, 4 and 6% of the soil dry weight and was designated as S0–S3, respectively. The water consumption, biomass, osmolytes, such as proline and Na+, and the activities of antioxidant enzymes, such as superoxide dismutase (SOD) and peroxidase (POD), of alfalfa were measured during its early flowering stage. In general, the plant height, aboveground biomass, root biomass and water consumption of alfalfa increased with the decrease in soil salinity and increase in the amount of irrigation applied. When the salt &gt;3 g kg−1, alfalfa could improve its stress resistance by increasing the contents of proline and Na+ and the activity of POD and decreasing the activity of SOD, but the aboveground biomass and water consumption decreased. However, alfalfa has a certain cross adaptation ability under water and salt stress at the branching stage, particularly when salt is less than 3 g kg−1. Compared with single water stress, adding an appropriate amount of salt (≤3 g kg−1) increased the contents of proline and Na+ and the activities of SOD and POD, which led to water consumption and aboveground biomass of alfalfa increases of 11.93% and 17.51%, respectively. In conclusion, the alfalfa was tolerant to moderate (3 g kg−1) salt stress. The alfalfa with higher proline, SOD and POD activity and Na+ was better able to yield well under salt stress. Meanwhile, combined with moderate irrigation (70–85% FC), the productivity of alfalfa was improved better. The results can provide a theoretical basis for the utilization of alfalfa in salinized land.

Spinach biomass yield and physiological response to interactive salinity and water stress

Taking into consideration that modeling and indicating relationship among traits and variables are among the most useful numerical techniques in the biological and botanical researches, and also undeniable impact of drought and salinity stresses, this research was implemented with the aim to consider change in relationship among the traits under separately drought and salinity stresses related to scarcely distributed medicinal plant called Christ thorn (Ziziphus spina-christi). A glass house experiment was implemented in controlled conditions at the College of Agriculture, Shiraz University, Shiraz, Iran. Five different water stress levels (irrigation at four, six, eight and 10 days intervals, compared to the unstressed control plants with every even days irrigation) and five salinity stress levels (0, 3.2, 6.4, 9.6 and 12.3 dS m-1) were separately induced on plants. Results of this study indicated that salinity and water stresses in addition to their destructive impact on cell and tissue compartment, can adverse and change the relationship among morphological and biochemical parameters in different ways. Cluster analysis could clearly separate traits into two groups under water stress while three groups under salinity stress. Principal component showed that this technique can accounted for a high variation among data under both water and salinity stresses so that it is possible to consider relationship among the traits using principal component in place of classic methods such as correlation coefficients. As result of principal component, it revealed that change in relationship among traits under different stresses is plausible.

New sources of water stress and salinity tolerances are needed for crops grown in marginal lands. Pepper is considered one of the most important crops in the world. Many varieties belong to the genus Capsicum spp., and display wide variability in tolerance/sensitivity terms in response to drought and salinity stress. The objective was to screen seven salt/drought-tolerant pepper accessions to breed new cultivars that could overcome abiotic stresses, or be used as new crops in land with water and salinity stress. Fast and effective physiological traits were measured to achieve the objective. The present study showed wide variability of the seven pepper accessions in response to both stresses. Photosynthesis, stomatal conductance and transpiration reduced mainly under salinity due to stomatal and non-stomatal (Na+ accumulation) constraints and, to a lesser extent, in the accessions grown under water stress. A positive relationship between CO2 fixation and fresh weight generation was observed for both stresses. Decreases in Ys and YW and increased proline were observed only when accessions were grown under salinity. However, these factors were not enough to alleviate salt effects and an inverse relation was noted between plant salt tolerance and proline accumulation. Under water stress, A31 was the least affected and A34 showed the best tolerance to salinity in terms of photosynthesis and biomass.

Population-based threshold models: A reliable tool for describing aged seeds response of rapeseed under salinity and water stress