CROP PHYSIOLOGY
Year:2010 | Volume:2 | Issue:2|Papers Count:10

In order to study of some physiological characteristics of two wheat cultivars under salinity stress this experiment was performed as a factorial test based on completely randomized design with three replications in greenhouse of agriculture faculty of Shahid Chamran University during 2008-2009. In this experiment, two factors were analyzed.First factor was cultivar, including Star and Chamran cultivars and the second factor, irrigation with saline water with three levels, including normal water and salt water (100 and 200 mM) with an equal quantity of NaCl and CaCl2 . The results showed that the most reduction in dry matter was achieved in second level of stress (200 mM) in Star cultivar. while salt stress was soaring, stomatal conductance in both studied cultivars was decreased further. Maximum reduction in stomatal conductance was observed in the second level of stress in Star cultivar.Intensifying of Stress levels caused the increase in soluble sugars accumulation in both cultivars but there were no differences between cultivars.By salinity treatment, proline accumulation significantly increased in in both studied cultivars. Both cultivars showed high ability to maintain RWC percentage, but by second level of stress; cultivars resistance were broken and RWC percentage, significantly decreased.The highest sodium content was observed in S2 of Chamran variety and the lowest level of sodium was observed in normal condition by Chamran cultivar.An increase in the ratio of K/Na significantly caused rising in SPAD value, while reducting RWC. In S1 condition, increasing of sodium concentration in plant leaves caused a sharp decline in the ratio of K/Na and the SPAD value (r2=-0.828**). Meanwhile this ratio with increasing potassium content increased (r2= 0.937**) and a rise in the ratio of K/Na led to raise of SPAD value. In normal conditions, as a result of elevating potassium, sugar transport was done in a better way, but in contrary, in severe stress conditions, increasing the amount of potassium, could not cause better sugar transport. It might be due to the lack of appropriate performance of sugar pumps because of damage of extreme salinity sress (200 mM).

To survey priming effect on germination of Corn seed (704 and 640 K.SC), the test executed as factorial completely randomized design in three replications in lab of agriculture faculty – Islamic azad university, Ghaemshahr branch in 2010. Treatments include seed of two Corn varieties (704 and 640) and seven solutions of PEG (prime polyethylene glycol) with density 5 and 10 percent, potassium nitrate (KNO3) with density 1 and 2 percent and potassium chloride (KCl) with density 2 and 4 percent, water and control (without pre treatment). Although no characterization did not show significant difference under effect of varieties statistically but results showed that the maximum speed of germination for hydro priming (water) and control (without pre treatment) resulted and the minimum length of rootlet for primed product of potassium nitrate and potassium chloride with densities 2 and 4 and the highest average for control (without pre treatment) resulted. The minimum length of stemlet for priming with potassium nitrate and potassium chloride with densities 2 and 4 percent resulted. The maximum index of germination and daily average germination and minimum average of germination time revealed priming by potassium nitrate and potassium chloride with densities 2 and 4 percent and control (without pretreatment) and the highest rate of dried weight of rootlet to stemlet resulted with potassium nitrate and potassium chloride with densities 1 and 2 percent. The lowest rate of wet weight of rootlet to stemlet resulted priming potassium nitrate and potassium chloride with densities 2 and 4 percent and also the maximum index of vigor 2 for hydro priming (water) and its minimum for primed solution of potassium chloride measured with 4 percent density.

In order to study the effect of different levels of nitrogen and plant population under different moist conditions on growth indices of grain corn (Zea mays L.) SC.704 a field experiment was conducted during 2008 and 2009 cropping seasons in Natural Resources and Agricultural Sciences University of Khuzestan, Ahvaz, Iran. This research in each year was made based on three split-plot field experiments, RCBD. Each of the irrigation treatments implemented separately in each experiment was Optimum irrigation (I1), Moderate stress (I2) and Sever stress (I3) (irrigation based on depletion of 30%, 40% and 50% of field capacity, respectively). Until 4 to 5 leaf stage (seedling establishment stage) irrigations applied after depletion of 30% field capacity in all treatments and after this stage irrigation treatments was applied. In each experiment three nitrogen levels (N 1=140, N 2=180 and N 3=220 kgN ha-1) were applied in main plots and subplots which consisted of three plant population (D 1=6, D 2=7.5 and D 3=9 plant. m-2). There were three replications for each experiment. Results indicated that the effect of water deficiency stress, nitrogen, and plant population on leaf area index, leaf area index of ear, above and under of ear at silking stage was significant. Leaf area index of ear, above and under of ear decreased as drought stress intensified. The highest leaf area index (4.9) was related to optimum irrigation. Decrease in relative water content of leaves caused decrease in growth and development of leaves and therefore, leaf area index reduced. Leaf area index increased significantly with increased nitrogen rate application. The positive effect of nitrogen application on leaf area index were considerably decreased as soil moisture content reduced. The increase of plant population, especially in optimum irrigation condition, caused a significant increase in leaf area index.As the highest leaf area index (5.4) obtained from 9 plant. m-2 at optimum irrigation treatment. The relative water content of ear increased significantly as water deficiency stress intensified and plant population increased, although differences between nitrogen levels for this trait was not significant. The highest and the lowest crop growth rate, relative growth rate and net assimilation rate obtained in optimum irrigation and severe drought stress treatments, respectively. The response of studied indices to the nitrogen application rate was positive. As plant population increased, crop growth rate increased but net assimilation rate declined, and relative growth rate remained unchanged. The results showed that selecting suitable treatments and change in leaf area index can cause plant growth increase and high yield access.

In order to compare the new broad leaf and grass herbicides with old ones and evaluation of their effects on yield and yield component of wheat (Chamran cultivar), an experiment was carried out in a completely randomized block design with 17 treatments and 4 repetitions in Ahvaz region in 2009. The treatments were: 3 grass herbicides (Topik, Axial and Traxos), 3 broad leaf herbicides (Granstar, Dialen super and Lintur), mixed of them, hand control and without control.Results showed that all parameters as biological yield, grain yield, harvest index and yield components (spike/m2, spiklet per spike, and seed per spiklet) with the exception of 1000 seed weight significantly affected by treatments.For all yield components with the exception of seed per spiklet the highest and lowest content recieved from hand control and without control treatments.Comparison between means showed that new herbicides and their mixture were better than old herbicides.Indices as Spike/m2 and spiklet per spike revealed the best effect on grain yield. It seems that lessening the efficacy of old herbicides, is due to mixing of these herbicides with each other and also applying herbicides recurrently, which provides the weeds a high level of tolerance to herbicides.

Corn as a main forage plant in temperate and warm regions of Lorestan province, shows a high reaction to manage to crop production elevation. In order to investigate the effect of planting pattern (a row and double row), nitrogen‘s fertilizer was applied in different stages of plant life cycle (during 4-8 leaf stage, 4-8 leaf stage and flowering stage and spraying between the rows during 4-8 leaf stage) and also weed control was done (hand weeding and no weeding or interference).This experiment was conducted by the factorial method with three repetitions in which a single cross 704 was used in Kamalvand (one of suburbs of Khorram Abad city) in 2009. Results showed that grain yield of two-row arrangement (4798 kg per hectare) compared to one row (3510.9 kg per hectare) was significantly superior. Lack of weed control caused a significant decline in grain yield by 3523.8 kg per hectare compared to hand weeding which was 4785 kg per hectare.There were no significant differences between different methods of nitrogen fertilizing in respect of seed yield.Arrangement of two rows in the set treated with complete weeding and nitrogen spraying during two stages (flowering and 4-8 leaf stage) was the best treatment with an average yield of 5779.7 kg per hectare.

This study was conducted to analyze the correlations between grain yield, yield components, and duration of vegetative and grain filling period of ten wheat (Triticum sativa L.) cultivars at Research Farm, College of Agriculture, Islamic Azad University Shoushtar Branch, during 2009-10.A randomized complete block design with four replications was done. Correlation coefficients between grain yield/m2 and fertile tiller/m2 )o.61 (, grain number/spike ) o.69 ( and duration of grain filling period ) o.66 ( were largely positively significant. Also Correlation coefficients between grain yield/m2 and 1000-kernel weight ) -o.43 ( and day to heading ) -o.55 ( were negatively significant. Among yield components, the number of spike /m2 and number of grain/spike revealed the largest direct effect on grain yield (0.40 and 0.57, respectively). Also duration of grain filling period showed the highest direct effect on number of grain/spike and 1000-kernel weight (0.49 and 0.13, respectively). The number of grain per spike showed indirect effect on 1000-kernel weight ) -o.65 (. The results of path analysis indicated that the number of spike /m2 and number of grain/spike exhibited the largest direct effects on grain yield. According to the direct effects of grain filling duration on number of grain/spike and 1000-kernel weight, and also considering this fact that most of the dry matter in wheat would be produced in this period, it seems that it is possible to examine these traits as selected criteria in breeding programmes for improving high yielding cultivars.

The present paper studies the effects of drought stress on morphological yield characteristics and yield component of wheat lines to identify the drought tolerance genotypes in Dezfoul region during 2007 cropping season. For this reason, randomized complete block design in three replications and on 16 lines of wheat form of two separate experiments were carried out. Primary experiment was carried out in complete irrigation conditions and the secondary experiment was in water stress conditions at the end of season. Based on the yield under drought stress (Ys) and non-stress (Yn) the drought tolerance indices: mean productivity (mp), Geometric mean productivity (GMP), harmonic mean (HM), stress tolerance index (STI), tolerance (TOL), stress susceptibility index (SSI) were derived at. Result of variance analysis showed a significant difference between the yield and yield component at level 1%, 5% under stress and non-stress conditions.furthermore highest seed production, biological yield, stubble yield, harvest index, 1000 grain weight, under conditions of stress and non-stress obtained in genotypes S78-11, Chamran, Chenab. results also showed highest seed yields of 4.640, 4.93, 4.73 ton/ha and highest biological yields of 12.93, 12.15, 12.69 ton/ha under non-stress conditions. Highest seed yields of 3.720 and 3.700 were obtained under conditions of stress in genotypes Chamran, S78-11. Cluster analysis of the results showed that the genotypes S78-11, Chamran, Chenab under stress and non-stress were in one group. Therefore genotypes 5, 8, 13 with most similarly were in another group. results of the interrelationship in non-stress showed indices HM, GMP, MP, STI, have most interrelationship with yield and most among interrelationship in non-stress under conditions with indices HM (r=0.930).

In order to study the effect of planting dates on silage yield of corn hybrids, an experiment based on split plot, RCB Design, with four repetitions was conducted in the spring of year 2009, in Khatam city. The main factor was planting dates with four levels as July 10, June 21, July 1, July 11, and subplots were corn varieties (DC 370, SC 400, SC 500, SC 647, SC 700 and SC 704 ). The analysis of variance was run and results showed that there were significant differences between planting dates, on plant height, stem diameter, stock grass yield and protein content, as well as significant differences among corn hybrids for considered characteristics. Comparison between means indicated that SC 700 hybrid was significantly higher in yield of silage (121.5 Ton per hectar) by date as of July 11, and also maximum content of protein (11.78%) was found in SC 500 hybrid on date of June 21.In the present study, analysis of our results showed that the best date for planting was June 11, and the best variety was SC 700.