فصلنامه پژوهشهای زراعی در حاشیه کویر
سال نهم شماره 1 (بهار 1391)

Salinity stress and its control which has been a major problem in agriculture since thousand years ago, can be considered as the main cause of reduction of production ability of arable lands in many countries. To evaluate the effects of different salinitylevels on seed germination components of four sesame cultivars Oltan, Darab 1,Dashtestan, and Mehr Sabzevar, a factorial experiment based on completely randomized design (CRD) with three replications was carried out in seed physiology lab. at Islamic Azad University of Bojnord. Salt treatments at 5 levels (0,4,6,8, and 10 ds/m)were applied with sodium chloride. Seeds of each cultivars were planted in plastic plates (5×8×11cm) containing different levels of salinity. Based on the analysis of data on seed germination and germination components, it was revealed that percentage and rate of seed germination were decreased with increasing salinity levels in all cultivars. Other germination components i.e. length of both radicle and plumle was also decreased. Cultivar Oltan was less affected by salt stress compared to the other cultivars.

In order to study the response of morphological traits, oil yield and seed yield components of sunflower hybrids to reduction source and sink quantity, an experiment was conducted in factorial based on RCBD with three replications at Aboureihan research farm of University of Tehran, Pakdasht, Iran in 2008. Azargol and new Iranian hybrid SHF81-90 and five levels of source and sink (removed 50% lower leaves, removed 50% upper leaves, removed 50% seeds and removed 25% seeds) and control treatment (without removing leaf and seed) were the factors. The results indicated that the effects of source and sink treatments were significant on stem diameter, head diameter, hollow diameter in head center, number of seed per head, 1000 seed weight, seed yield per hectare, oil percent and oil yield per hectare. The effect of hybrid was significant on all mentioned traits except stem diameter and oil percent. Intractions were significant on stem diameter, head diameter, hollow diameter in head center and seed yield per hectare. However height and number of leaf did not affect by any of the treatments and intractions. The highest seed yield 6569.3 kgha-1 obtained from SHF81-90 in control treatment.

In order to investigate the effects of seedling age and potassium rates on lodging related characteristics and agronomical traits in rice, an experiment was carried out in split plot based on randomized complete block design with four replications at Mazandaran province in 2009. Main plot was seedling age in three levels 20, 30 and 40 days and sub plot was potassium rates in four levels 0, 60, 120 and 180 kgha-1. Results showed that third inter-node length, diameter and bending moment, fourth inter-node diameter and bending moment, panicle length, total tiller number per hill, filled spikelet percentage, panicle number per m2, grain yield and harvest index had significant differences (p ≤ 0.01 and p ≤ 0.05). The maximum length, diameter and bending moment of the third and fourth inter-node and grain yield were obtained with application of 180 kg K per hecare. The highest number of panicle per m2 was produced at interaction of 40 days seedling age × 60 kgha-1 and the maximum grain yield and biological yield were produced at interaction of 30 days of seedling age × 120 kgha-1. Therefore, 30 days seedling age and application of 180 kgha-1 that produced the highest grain yield, biological yield and harvest index was determined as the best treatment.

Five cultivars of five species of annual medics, Medicago truncatula cv. Mogul, M. scutellata cv. Sava, M. minima cv. Orion, M. litttoralis cv. Herald, and M. polymorpha cv. Santiago were studied for seed production in three plant densities (20, 30 and 40 cm distance between two plants on row) at research field of Agricultural College of Tarbiat Modarres University in 2007. A factorial experiment in base of randomized complete block design was used with three replications. Based on the results of the experiment, Santiago and Sava cultivars had the highest seed yield, respectively, and Sava cultivar had the highest pod yield. The highest seed yield and pod yield of cultivars, was produced at 20 cm plant distance on the row. Number of plants was not adequate for production of maximum seed and pod yield in 30 and 40 cm distance treatments. The tested plant densities did not affect seed numbers per pod, thousand seed weight and seed to burr pod weight ratio. Mogul and Orion had the highest seed numbers per pod. Sava had the highest thousand seed weight (12.57 g). The highest seed to burr pod weight ratio was observed in Santiago. Santiago also. produced the highest number of pods in 20 and 30 cm distances on row, and Sava. produced the minimum numbers. The results indicated that seed production of tested annual medics with suitable plant densities in the mentioned area would be possible.

In order to study the effects of six levels of drought stress (0, -3, -6, -9, -12 and -15 bar applied by PEG 6000) on seed germination components of seven autumn safflower cultivars CH353, CH65, Asteria, CH697, Rinconada, Zarghan and Golsefid Esfahan, an experiment was conducted in factorial form using a completely randomized design with four replications at Islamic Azad University, Bojnourd Branch in 2008. Germination percentage, mean germination time, coefficient of velocity of germination (C.V.G.), germination rate, radical length and shoot length were measured in each treatment. Significant differences were observed for all traits among the cultivars and different levels of drought stress. All traits decreasedsignificantly with increase in stress level. Interactions between stress level and cultivar were also significant for all traits except germination percentage and root length. The lowest germination percentage was observed in CH697 and the highest mean germination time belonged to CH697 in -15 bar. Cultivars Rinconada and Golsepid Esfahan had the lowest germination time and the highest germination rate and C.V.G. in O and -3 bar. CH697 had the lowest radical length and Golsepid Esfahan had the longest shoot in 0 bar. Shoot length was highly affected by stress level. Based on these results, it was cleared that cultivar CH697 was the most susceptible and CH353 and CH 65 the most tolerant cultivars.

In order to study the effects of drought stress on morphologic, agronomic characteristics and fodder yield of fourteen new forage corn hybrids, an experiment was conducted at the experimental field of Seed and Plant Improvement Institute, Karaj, Iran in 2009. The experiment was carried out using split-plot in a randomized complete block design with three replications. The main plots consisted of three levels of irrigation regimes (irrigation after 70, 100 and 130 mm cumulative evaporation from evaporation pan class A) and sub-plots included 14 new corn hybrids. Dry fodder yield, plant height, leaf number, stem diameter, dry leaf to stem ratio, percent ear to total dry fodder were evaluated. The results showed that differences among hybrids were significant for plant height, dry leaf to stem ratio, leaf number and percent ear to total dry fodder. No significant differences was observed among hybrids for stem diameter. Also, All of the traits decreased under drought stress conditions. Increasing in irrigation intervals decreased dry fodder yield up to 45%.

To assess the quantitative and quantitative traits of KSC704 corn hybrid under drought stress and nitrogen fertilizer levels, an experiment was carried out in research farm of Islamic Azad University in Varamin in 2009, using a split-plot based on randomized complete block design with four replications. The main plot consisted of four levels of drought stress (0, 100, 150, and 200mm evaporation from evaporation basin A pan) and subplot was three levels of nitrogen fertilizer (80, 130, 180kg, pure nitrogen per hectare). Assessment of different traits showed significant differences among them in different treatments of drought stress and nitrogen levels. These treatments affected grain yield either through total number of grains per ear or 1000 grain weight. The highest grain yield 8919 and 7078kg ha-1. were obtained in treatments of 50mm evaporation and 180 kg nitrogen, respectively. Studying the growth trend, it was clear that the effect of drought stress on stem dry weight at the end of season was more than that on dry leaf weight. Drought stress in the second half of growth season decreased stem dry weight significantly but had no effect on leaf dry weight, indicaling that drought stress increased dry matter remobilization from stem to grains. In addition, total dry weight was decreased significantly with increasing water stress. Changes in relative water contents as influence by irrigating regime, and nitrogen fertilizer, demonstrated the effects of experimental factors on resource strength. Accumulative increase of nitrogen led to reduction of drought strength. Accumulative increase of nitrogen led to reduction of drougth stress effects due to increase of relative water contents and consequently decreasing of catalase enzyme’s activity.

In order to evaluate reaction of grain yield and some of safflower physiological traits to water stress and zeolite application, an expriment was carried out in research field of Arak University in 2009. Statistical design was split plot adopting complete randomized block with three replications. Water stress (I0: Control irrigation, I1: irrigation about 85% plant requirement water, I2: irrigation about 70% of plant requrment water, I3: irrigation about 55% of plant requirement water), were assigned in the main plots and different levels of zeolite application (Z0: without zeolite application, Z1: 3 ton ha-1, Z1: 6 ton ha-1, Z1: 9 ton ha-1) in sub plots. Characteristics such as height of the first branch, stem diameter, biological yield, grain harvest index, cell membrane instability, relative water content, initial water content, saturate water deficit and rate of water loss were assessed. The results indicated that un-stress irrigation (control irrigation) with grain harvest index of 25/46 % and zeolite application of 9 ton ha-1 with grain harvest index of 24/84 % significantly affected all measured traits and superior to the other treatments.