مجله تنشهای محیطی در علوم زراعی
سال هشتم شماره 1 (نیمه اول 1394)

In Iran where main part of precipitation takes place during winter and spring، wheat is dependent on water conserved in sub soil especially at rain-fed cultivation system. To find the genotypes with good root system at sub soil depth an experiment was conducted with 63 bread wheat genotypes planted in one meter long PVC tubes under non stress and drought stress condition. Under non-stress condition irrigation was conducted regularly while under stress condition it was delayed until soil moisture was depleted to 30 percent of filed capacity. After applying stress and at the end of growth season root related traits in four depth (0-20، 20-40، 40-60 and 60-100 cm) along with yield and its components were measured. The results showed high variation among genotypes for all traits. High significant correlations were observed between total root weights with yield under stress condition (r=0. 58، p=0. 01). A unit increase in root dry weight added 0. 24 g to grain yield in each plant. Separate correlation analysis for each profile showed that the effect of root dry weight at deepest profile on yield was higher than other profiles (r=0. 75، p=0. 01). Under stress condition the effect of root weight at 60-100 cm depth on yield was positive and highly significant. Genotypes of Sardari، Sholeh، Naz and Inia were best genotypes considering root dry weight at this profile with 0. 44، 0. 39، 0. 37 and 0. 37 g/plant، respectively.

In order to study the genetic variation، identification and selection among wheat genotypes based on indices of drought stress، this experiment was conducted with 16 bread wheat genotypes that arranged a randomized complete block design and three replications in two normal and restricted irrigation at the Neishabour Agricultural Research Station during 2008-09 cropping season. Seven drought stress indices were Mean Productivity (MP)، Geometric Mean Productivity (GMP)، Harmonic Mean (HMP)، Stress Tolerance Index (STI)، Stress Susceptibility Index (SSI)، Tolerance Index (TOL) and Lin and Binns (Pi) method. The highest grain yield in stressed environment and the greatest values of MP، GMP، HARM، STI and Pi obtained in With regard to above mentioned indices and grain yield in two conditions، lines no. 2، 11 and 14 were the best tolerated drought stress genotypes. Analysis of correlation and mean grain yield in two conditions showed these indices suitable for screening genotypes under these conditions. Using multivariate biplot showed which genotypes no. 2، 11 and 14 were adjacent drought tolerance indices i. e. MP، GMP، HARM، and STI. Cluster analysis revealed genetically distance between genotypes، that genotypes no. 2، 11 and 14 as drought tolerated and genotypes no. 3، 8، 9 and 13 were susceptible to drought stress respectively.

In order to investigate the time of potassium application and irrigation regimes effects on agronomic traits، yield and seed quality of foxtail millet، a field experiment was conducted as split plot based on randomized complete block design with three replications at Agricultural Research Center of Yasuj، Iran، during 2009. The experiment was conducted in split plot design based on randomized complete block design with three replications. The irrigation regimes included: 7، 14 and 21 day intervals as main plots and sub-plots including potassium fertilizer application in four stages of planting، tillering، stem development and flowering. The results showed that the effect of irrigation regimes was statically significant on plant height، leaf number، ear size، grain yield، leaf chlorophyll content، water soluble carbohydrate and protein percentage. By increasing the irrigation period، all of the above mentioned traits were decreased، except protein percentage. Also time of potassium application significantly affected plant height، grain yield، leaf chlorophyll content، water soluble carbohydrate and protein percentage، so that potassium application until flowering stage increased the studied traits. The interaction effects of irrigation and potassium application on plant height، seed yield، leaf chlorophyll and soluble carbohydrates was significant. The maximum seed yield was obtained by using potassium at the stem development stage and 7 days irrigation regime، and the maximum seed protein percentage was obtained in 21 days irrigation regime and potassium application at flowering stage.

In order to study of agronomic، physiologic and qualitative characteristics of Canola (Brassica napus L.) under stress irrigation، an experiment was carried out as randomized complete block designs with three replications at the research field of Shahr-e- Qods Branch، Islamic Azad University، in 2010-2011 year. In this experiment، the irrigation treatment in three levels were including optimize irrigation in total growth period based on 80 millimeter evaporation from class A evaporation pan (control)، stress irrigation from flowering until physiologic maturity، and stress irrigation from silique formation until physiologic maturity، respectively. The results indicated that effect of irrigation treatment on plant height، stem diameter، branch per plant، relative water content (RWC)، water saturation deficiency (WSD)، Chl a and carotenoid، silique length، silique per plant، 1000 seed weight، seed yield، seed oil content، oil yield، harvest index and productivity effort were significant. Stress irrigation from flowering and silique formation decreased the RWC by 43. 1 and 29. 5، Chl a by 32. 7 and 26. 5، and carotenoid by 49. 6 and 31. 8، respectively، in compared to control treatment. In this study، normal irrigation (control) showed the highest seed yield. Seed yield was reduced from 2577 kg. ha-1 at control to 1483 and 1907 kg. ha-1 in stress irrigation from flowering and silique formation، respectively. Positive correlations were observed between seed yield and yield components، except seed number per silique and greteast correlation occurred between seed yield and 1000 seed weight and silique per plant، respectively. Overall، these results showed that stress irrigation from flowering until physiologic maturity had the adversely effects on physiologic and morphologic characteristics and seed yield and dependent traits in compared to stress irrigation from silique formation until physiologic maturity

In a greenhouse experiment، the effect of four salinity levels (1، 2، 4 and 8 dS m-1) and three levels of urea fertilizer (200، 300 and 400 kg urea ha-1) on growth parameters، cane juice ionic composition and uptake of some nutrients by sugarcane variety CP69-1062 was studied. The experiment was factorial in a randomized complete block design with three replications. The results showed that length and dry weight of root and consequently shoot dry weight including weight and number of cane and plant biomass per pot significantly decreased as salinity was increased from 1 to 8 dS m-1. The highest root dry weight and total root length were observed in treatment of 400 kg urea ha-1 and salinity of 1 dS m-1، and the lowest weight and length of root in treatment with 200 kg urea ha-1 and salinity of 8 dS m-1 were observed. Na concentration in plant subjected to salinity stress was reduced as urea fertilizer was increased، while K uptake was increased and this led to an increase in K: Na ratio in both leaf and cane juice، more proline accumulation and finally increase in weight of cane. Electrical conductivity، ash and Na concentration in cane juice were significantly increased with increasing salinity. The results of this study confirm the hypothesis that detrimental effect of salinity on plant can be reduced by enough N fertilizer application.

Drought is one of the most important limiting factors on plants growth which limit about 25 percent of arable lands production over the world. The objective of the present study was to investigate the effect of drought stress and phosphorus and zinc fertilizer levels on the quantitative and qualitative properties of German chamomile (Matricaria recutita cv. Gural). The experiment was conducted at Research farm of University of Zabol in 2013. The experiment was a split plot factorial in a randomized complete block design with three replications. Treatments consisted of three irrigation levels (75% (control)، 50% (mild stress) and 25% of field capacity (severe stress)) as main plots، and factorial combinations of three triple superphosphate fertilizer CaH4P2O8 levels (0، 150، and 300 kg ha-1) and two zinc sulphate fertilizer ZnSO4 (H2O) levels (0 and 30 kg ha-1) as sub plots. Some traits such as plant height، number of flowers per plant، flower diameter، fresh and dry flower yield، root length and essence yield were measured. The results showed that drought stress significantly reduced values for all morphological traits، except root length. However، no significant mild stress effect was observed for essential oil content. The application of 150 kg P fertilizer ha-1 and 30 kg Zn fertilizer ha-1 increased essential oil content and values for morphological traits. The application of 300 kg P fertilizer ha-1 had negative effects on chamomile yield. In general، the results of this experiment showed that the application of 150 kg P fertilizer ha-1 and 30 kg Zn fertilizer ha-1 under mild stress (50% of field capacity) can improve essential oil content in German Chamomile.

This study was carried out to investigate the effects of salinity and putrescine on pot marigold. Plants were treated with sodium chloride solotions which their electrical conductivity (EC) were adjusted at 1، 3، 6 and 9 ds/m and putrescine spray at 0، 1 and 2 mmol. The experiment was factorial based on a completely randomized design (CRD) in greenhouse condition Stomatal length average on abaxial and adaxial sides of leaf، chlorophyll index، minimum and maximum florescence (F0 and Fm respectively) and photosystem II quantum yield were measured during the experiment. Result showed that salinity had significant effects on all characteristics. Generally all characteristics were reduced by increasing salinity levels except F0 and Fm. Chlorophyll index، quantum yield and stomatal length average on both leaf sider were reduced up to 30%، 27. 3%، 5%، 23%، 22. 3% and respectively، while F0 and Fm increased by salinity. Moreover، putrescine reduced the negative effects of salinity on chlorophyll index، stomatal length average on both leaf and quantum yield. putrescine also reduced the length of stomatal.

Nowadays medicinal plants are considered as economically important plants throughout the world، while basic information on these plants is scarce. This study was aimed to quantify germination rate response of annual savory (Satureja hortensis L.) to temperature and salinity stress. For this purpose، seeds were exposed to different temperature (12، 15، 20، 25، 30، and 35 ͦ C) and salinity levels (0، 25، 50، 75، 100، 125 and 150 m M) treatments in Seed Research Lab.، Gorgan University of Agricultural Sciences and Natural Resources in 2013. Results indicated that temperature and salinity stress simple and interacted effects had significant effect on maximum germination percentage (MGR)، germination rate (reciprocal time to 50% germination)، and time elapsed to reach 10، 50 and 90% germination. Along with salinity levels increment، both germination percentage and rate decreased. With temperature increasing to optimum temperature، both germination percentage and rate increased، while it decreased from optimum temperature onward. Assessment of three nonlinear regression models including segmented، dent-like and beta models revealed that the last one was the superior model. Base on the superior model (Beta)، base، the optimum and ceiling temperatures were estimated as 8، 24. 77 and 41 ͦ C، respectively. Biological hours for control treatment (zero salinity level) were calculated as 83. 68 hours. Optimum and ceiling temperatures were not affected by salinity stress، but base temperature and biological hours for germination was delayed as 1. 35 ͦC decrement and 1. 65 hours increment per each 25 m molar salinity levels.

Nowadays medicinal plants are considered as economically important plants throughout the world، while basic information on these plants is scarce. This study was aimed to quantify germination rate response of annual savory (Satureja hortensis L.) to temperature and salinity stress. For this purpose، seeds were exposed to different temperature (12، 15، 20، 25، 30، and 35 ͦ C) and salinity levels (0، 25، 50، 75، 100، 125 and 150 m M) treatments in Seed Research Lab.، Gorgan University of Agricultural Sciences and Natural Resources in 2013. Results indicated that temperature and salinity stress simple and interacted effects had significant effect on maximum germination percentage (MGR)، germination rate (reciprocal time to 50% germination)، and time elapsed to reach 10، 50 and 90% germination. Along with salinity levels increment، both germination percentage and rate decreased. With temperature increasing to optimum temperature، both germination percentage and rate increased، while it decreased from optimum temperature onward. Assessment of three nonlinear regression models including segmented، dent-like and beta models revealed that the last one was the superior model. Base on the superior model (Beta)، base، the optimum and ceiling temperatures were estimated as 8، 24. 77 and 41 ͦ C، respectively. Biological hours for control treatment (zero salinity level) were calculated as 83. 68 hours. Optimum and ceiling temperatures were not affected by salinity stress، but base temperature and biological hours for germination was delayed as 1. 35 ͦC decrement and 1. 65 hours increment per each 25 m molar salinity levels.

Seed dormancy is one of the major problems in evaluating the effect of different environmental factors on germination characteristics of weed seeds. In order to realize the type of Mesquite seed dormancy an experiment were conducted based on a completely randomized design (CRD) with twelve treatment and four replications. Treatments were six different times seed soaking (10، 20، 30 40، 50 and 60 minutes) in sulfuric acid 95-98%، mechanical scarification with sandpaper for 5 minutes، seed soaking in distilled water at 24 and 48 hour and soaking seeds boiling water (95-98 0C) for 5 and 10 minutes with control. Results showed that all chemical and mechanical scarification treatments germination was conducted and highest germination rate، root and stem length، root and stem fresh weight were in time 60 minutes of seed storage in sulfuric acid. In order to study effects of salt and drought stress (as NaCl and PEG6000) on germination characteristic of Mesquite two separate experiment were conducted in growth chamber. The Experimental design was a completely randomized plot design (CRD) with four replications. Treatments were salt and drought stress as osmotic and matric potential، respectively، at four levels (0 (distilled water)، -0. 3، -5، -10 and -15 bars). Result showed when stress increased، germination percent، germination rate decreased significantly (p≤ 0. 001)، there were higher in drought stress than salt stress. When water potential decreased، time to 50% of maximum germination increased. The functional three-parameter logistic model provided a successful estimation of the relationship between salt and drought stress levels and germination response of Mesquite. Results of this model showed that salinity and drought at -16. 23 and -6. 26 bar، respectively caused 50% reduction in maximum germination percentage of Mesquite.

In order to evaluate cold tolerance of Lancelot Plantain plant a Factorial experiment based on completely randomized design with three replications was conducted under controlled conditions in faculty of agriculture، Ferdowsi University of Mashhad. Experimental factors include plantain ecotypes (Bojnord، Kalat، Mashhad، Ghayen and Birjand) and freezing temperatures (0، -3، -6، -9، -12، -15، -18 and -21°C). Plantain plants after 3 months growth and hardening in natural environment for applying of freezing temperatures were transferred to a Thermo gradient freezer on January20، 2012. In order to assess plasma membrane stability، electrolyte leakage percentage (EL %) and the lethal temperature 50% of plants according to the EL% (LT50el) was determined. Plant survival assessed four weeks after freezing treatment by measuring survival percentage and the lethal temperature 50% of plant according to the survival% (LT50su). Results showed that at the case of LT50el، Mashhad ecotype was the most tolerant and Kalat and Birjand ecotypes were the most sensitive ecotypes. Ecotype and temperature interactions had noticeable effects on EL and Survival percentage، so in -12 °C، Bojnord and Birjand ecotypes had the least and the most EL% respectively. In the same treatment Mashhad ecotype with 94. 4 % and Birjand ecotype with 25. 4% exhibited the most and the least survival percentage. The value of LT50su for Mashhad ecotype was 5. 3°C lower than Birjand ecotype. There was high and negative correlation between EL% and survival percentage (r=-0. 70**) in this survey. Moreover there was significant and positive correlation between LT50el and LT50su (r= 0. 53*). According to these findings، Mashhad and Bojnord ecotypes exhibited suitable freeze tolerance than Birjand ecotype.

In order to study the effect of drought stress on according to irrigation intervals (7days and 10days) on grain yield of four maize single cross hybrid (500، 647،700 and 704) a split plot experiment based on randomize complete block design with 3 replications was done at Khatam during 2009. Plant height، number of row in ear، number of grain in row، number of grain in ear، ear length، ear diameter،ear wood weight، 1000 grain weight، biological yield، grain yield and harvest index were measured. The results showed that drought stress caused a significant decrease on all traits and decreasd grain yield 10. 2 to 5. 5 ton/ha. It was significant different between hybrids in grain yield. The highest grain yield was produced by KSC704 (11. 2 ton/ha) and lowest grain yield was produced by KSC500 (3. 9 ton/ha). The highest MP، GMP، STI and the lowest TOL and SSI indices was for KSC704 that indicated KSC704 is the most resistant hybrid to drought stress.

The aim of this study was to find out the effects of salinity stress along with Salicylic and Ascorbic acid priming on seed germination of Trifolium repens and Trifolium pratense (native) and Trifolium pratense cv. Marino. A factorial experiment based on completely randomized design was conducted using salt stress at 4 levels (0، 100، 150 and 200 mM) and 5 levels of alleviators (0، 100 and 200 ppm of each) with 3 replicates. Results showed that salt stress، interaction between salinity and alleviator and 3 way interactions had significant effects on measured traits (P≤0. 01). Highest and lowest values measured for different traits in this experiment were in control and higher salinity treatments، respectively. Germination percentage in the highest levels of salinity (200 mM) in T. repens، T. pratense (native) and T. pratense cv. Marino were 90، 77 and 78% respectively، compared to the control and applying Ascorbic acid (200 ppm) at the same level of salinity improved germination percentage by 88، 71 and 70%، respectively. Similar results were obtained for germination rate. In general، although salinity stress markedly reduced both germination percentage and rate، but using alleviators such as، salicylic and ascorbic acid recovers undesirable effects of salt stress and increases germination percentage and germination rate significantly.