Environmental stresses such as drought have important effects on plant growth and development. In order to evaluate the effect of drought tolerance, 12 chickpea genotypes were treated with drought stress in hydroponic condition in greenhouses. Treatments were a control and two stress treatments -3 and -6 bar that was created with polyethylene glycol in hydroponic condition. Two weeks after the stress treatments on the genotypes, moisture content, OSMOTIC POTENTIAL, proline and soluble sugars were evaluated in their shoot and root. Results showed that drought stress reduced moisture content in shoot, but moisture content in the root had no significant changes. On the other hand amount of OSMOTIC POTENTIAL, OSMOTIC compounds and proline increased in response to drought stress in shoot and root. Drought tolerance index in genotypes showed positive significant correlation with amount of the root OSMOTIC compounds in -3 bar treatment. Despite the absence of significant changes in leaf soluble sugars, the amount of root soluble sugars declined in stress treatments compared to control. In addition, the positive significant correlation was observed between the drought tolerance index in -6 bar treatments and root soluble sugars of this treatment. Leaf and root proline levels had not significantly correlation with drought tolerance in genotypes. Despite some correlations between traits and drought tolerance index it seems that OSMOTIC adjustment, moisture content, proline and soluble sugars alone not to be a suitable indicator to evaluate drought tolerance in chickpea genotypes.

Physiological response of Haloxylon aphyllum to drought stress was evaluated in Shahid Sadouqi desert research station of Yazd with geographical coordinate of 54, 11" 9" longitude and 32, 4', 30" latitude during 2001-2005. A factorial experiment based on completely randomized design with 3 replications was applied. After planting and establishment stages, the experimental treatments including pot capacity, one third capacity and non-irrigation were applied in weighing lysimeters. Experimental treatments were applied in the second year and then physiological characters including plant water POTENTIAL, leaf OSMOTIC POTENTIAL and root OSMOTIC POTENTIAL were measured from late June until late September in 15 day intervals. To evaluate the interaction of environmental factors, such as temperature on physiological factors, the measurements were done just before sunrise and in the afternoon. Results showed that plant water POTENTIAL, leaf OSMOTIC POTENTIAL and root water POTENTIAL were significantly (p<0/01) affected by the treatments. Recording date also affected significantly (p<0/01) the physiological traits. On the other hand, results showed that haloxylon drought resistance is partly related to low water POTENTIAL in plant due to low leaf OSMOTIC POTENTIAL. Variation of OSMOTIC POTENTIAL along experimental period showed high OSMOTIC adjustment capacity in plant.

Introduction: Seed germination is a complex biological process that is influenced by various environmental and genetic factors. Temperature and water POTENTIAL are two primary environmental regulators of seed germination. Quantification of germination response to OSMOTIC POTENTIAL and temperature is possible using non-liner regression models. Tall mallow (Malva sylvestris) is an important invasive weed in southwest Iran and also a medicinal plant.). Tall mallow is native home in Western Europe, North Africa and Asia. This plant frequently found in cultivated fields, orchards, gardens, farmyards near manure piles, along roadsides, in towns, and in waste places and, can grow anywhere from 60 to 120 cm in length. Not published information exists concerning effect of OSMOTIC POTENTIAL on cardinal temperatures, Therefore, the objective of this research was to evaluate the effect of OSMOTIC POTENTIAL and different temperatures on germination and determination cardinal temperatures (base, optimum and maximum) of Malva sylvestris under OSMOTIC stress.Material and methods: In this study germination response to water POTENTIAL in different temperature were studied. Treatments included OSMOTIC levels (0, -0.2, -0.4, -0.6 and -0.8 MPa) and temperature (5, 10, 15, 20, 30, 35 and 40oC). Cumulative germination response of seeds to differential water POTENTIAL and temperature were quantified using three-parameter sigmoidal model. For quantifying response of germination rate to temperature for different OSMOTIC POTENTIAL were used of 3 non-linear regression models (segmented, dent-like and beta). The root mean square of errors (RMSE), coefficient of determination (R2), CV and SE for relationship between the observed and the predicted germination percentage were used to select the superior model from among the employed methods. Germination percentage and time to 50% maximum seed germination of Malva sylvestris were calculated for the different temperatures and OSMOTIC POTENTIAL by fitting 3-parameter sigmoidal functions to cumulative germination data.Results: Results indicated that temperature in addition to germination percentage also on germination rate was effective. Also results showed that germination percentage and germination rate increased with increasing temperature, while germination percentage and germination rate reduced as a result of water POTENTIAL increment. Results indicated that under different OSMOTIC POTENTIAL as 0, -0.2, -0.4, -0.6 and -0.8 MPa, the segmented model estimated base temperature as 1.46, 1.82, 1.29, 0.43 and 4.06 °C, the dent model estimated base temperature as 1.23, 1.82, 3.04, 2.63 and 4.07 °C, the beta model estimated base temperature as -4.32, 4.46, 1.86, 1.61 and 4.13 °C, the segmented model estimated optimum temperature as 28.29, 27.58, 22.24, 22.51 and19.69 °C, the optimum temperature using beta model as 27.89, 25.41, 23.18 and 21.05 °C, the dent-like model estimated lower limit of optimum temperature and upper limit of optimum temperature as 23.16 and 33.58, 16.86 and 30, 16.1 and 25, 15.81 and 25, 19.51 and 1987 °C, ceiling temperature using segmented model were 42.9, 40, 40, 40 and 34.96 °C, using dent-like model were 42, 40, 40, 40 and 34.96 °C, using beta model were 42.01, 40.02, 39.96, 39.98 and 34.83 °C, the segmented model estimated fo as 13.87, 18.45, 19.43, 25.24 and 36.13 h, the dent-like model estimated as 16.65, 23.28, 23.43, 30.48 and 36.56 h and using beta model were 16.06, 21.34, 22.21, 28.92 and 42.89 h, respectively. In compared 3 models according to the root mean square of errors (RMSE) of germination time, the coefficient of determination (R2), CV and SE the best model for determination of cardinal temperatures of Malva sylvestris for 0 to -0.6 MPa was dent-like model and for -0.8 MPa was segmented model. In general, results indicated that lower limit of optimum temperature and upper limit of optimum temperature and ceiling temperature reduced but fo increased as a result of water POTENTIAL increment.Conclusion: Germination of Malva sylvestris response to different temperatures and OSMOTIC POTENTIALs, led to acceptable results. Utilizing the output of non-liner models at different temperatures can be useful in prediction of germination rate in different water POTENTIAL.

To control water POTENTIAL in seed germination studies OSMOTIC solution of polyethylene glycol (PEG) are commonly used environmental stress, such as drought and (OSMOTIC) stress can play an important role in disturbing different stage of medical plant growth, development, and especially seed germination in arid and regions high percent of medicines are used for people have plant origin. With attention to the development of drought area and the shortage of agricultural area, it comes in to great importance to make use of drought tolerant plant an experiment was carried out in order to study the effect of different drought (OSMOTIC) levels on Cuminum Cyminum in germination in a completely randomized design with three replications. Drought (OSMOTIC) levels applied were zero (Control), 5%, 10% and 15% (0, -0.03, -0.19 and -0.41 Mpa). The purpose of this study was to determine genotype in PEG solution had a detrimental effect on germination percentage and germination rate.

Soil salinity threat for agricultural ecosystems in many parts of Iran, and negatively affects crop production.In order to examine salinity tolerance of Kochia a series of experiments were conducted in CRD with four replications, seven levels of salinity (0, 10, 20, 30, 40, 50 and 60 dS.m-1), two growth stages (planting and early seedling) and interval irrigation. Result showed that decrease of root dry weight, root volume, membrane stability index were more increased at planting than early seedling stages. Relative water content was increased with increasing salinity levels in all experiments except at interval irrigation. Proline and OSMOTIC POTENTIAL increased with increasing salinity levels. Catalase, glutathione reductase, DPPH - radical scavenging activities and total phenol were higher with more increased at planting than early seedling. Sodium concentration and sodium to potassium ratio in shoot and root increased with increasing salinity levels. Generally, despite application of high levels of salinity stress kochia was able to survive and tolerate these levels of salinity.

The world is facing a dwindling supply of water, therefore deficit irrigation is becoming more of a necessity than a choice. Partial rootzone drying (PRD) is a new water saving irrigation technique where at each irrigation time only one part of the rootzone is watered. The un-irrigated part is watered during the next irrigation. We explored the POTENTIAL of PRD for `Petopride´ processing tomato. There were two treatments: control (C, normal irrigation) and PRD. We collected data on water relations of vegetative and reproductive organs. PRD saved water by 50% and increased water use efficiency of the plant compared to C. Leaf water POTENTIAL was more negative under PRD compared to C. Irrigated and non-irrigated roots of PRD had similar water POTENTIAL and this could have happened by water movement between the two sides of root system. Water POTENTIAL of fruit was lower in PRD than in C.But pressure POTENTIAL (turgor POTENTIAL) was similar between PRD and C fruit. This was indicative of OSMOTIC adjustment (osmoregulation) in PRD fruit. To our best knowledge, this is the first report of OSMOTIC adjustment of fruit under PRD treatment.