فصلنامه گیاه و زیست بوم
پیاپی 19 (پاییز 1388)

Water logging has a major impact on both natural vegetation and agricultural crops. Soilwater logging occurs when over irrigation and excessive rainfall combine with poordrainage. The most detrimental effect of water logging is oxygen deficiency in the soil,because roots are particularly sensitive to anaerobic conditions, which can severely affectnutrient relations of the soil. Leaf epinasty, lateral root production, internodes elongation, were observed in flooded plants, which probably is the result of increasing ethylene production by plants. One of the morphological and anatomical mechanisms for acclimation of plants to flooding stress probably will be the avoidance of water loss by transpiration. The other will be a facilitation in transport of atmospheric O2 to the submerged roots by formation of adventitious roots and aerenshyma. However, comparison of microscopic section showed that in stem of treated with 5 and 7 days flooding, aerenshyma formed.

In order to study some of the physiological responses of sugar beet plant to salinitystress, A 4- replicate CRD greenhouse experiment was conducted with five salinity levels(o, 85, 171,256 and 342 mM Nacl). Seeds were planted in greenhouse and plantlets irrigated by Hoagland nutrition solution. Total dry weight, Leaf area, total Leaf chlorophyll, proline in shoot and Na+, k+ in the leaves were measured at the final leaf growth stage. Results showed that with increasing salinity levels total Leaf chlorophyll, Leaf area and total dry weight decreased, while proline content in shoots and Na+ in leaves significantly increased with increasing salinity levels. K+ content in leaves decreased with increasing salinity stress. Accumulation of Na+ in the leaves particularly at high salinity levels lead to nutrient deficiency, ionic toxicity and growth decrease. The high level of proline enhanced the plant to maintain osmotic adjustment when growing under low water potentials.

Allelopathy is an interference mechanism in which living or dead plants releaseallelochemicals exerting an effect (mostly negative) on the associated plants, and this might be a chance to reduce the use of herbicides and could be an additional tool to control herbicide-resistant weeds. The species of Brassica tissue such as rapeseed could beattributed to their ability to release toxic substances in the environment and to create anunfavorable environment for weed germination and establishment. The objective of thisstudy was to select suitable cultivars of rapeseed with high allelochemical and use of themin weed management. Accordingly, an experiment was carried out to assess allelopathicpotential of cultivars of rapeseed vegetative parts on some common weeds in Kermanshahregion (wild barley, wild oat, tumbleweed amaranth and curly dock) in randomizedcompletely block design. The factors consisted of cultivars (opera, talaieh and okapy) ofrapeseed and concentration (100%, 50% and control).Measured traits were germinationpercentage, inhibitory percentage, speed of germination, rootlet length and hypocotyllength. The bioassay experiments showed that by increasing the aqueous extractconcentrations of rapeseed’s cultivars, the germination rate and seedling crops of weed were decreased (P < 0.001). Especially the residual extract of rapeseed had most effect on germination and seedling growth of tumbleweed amaranth. In particular, opera extractscaused greater inhibitory percentage on weeds than talaieh and okapy.

Cyanide is a Co-product of ethylene biosynthesis in higher plants via the ACC pathway.In certain physiological, such as fruit ripening, flower senescence, flooding, drought,pathogen infection, ozone, UV radiation and chilling, ethylene biosynthesis is greatlyinduced. Cyanide is a harmful ion, hazardous to life, which forms a very stable complex with the active site metal (e.g., Fe and Mg) in enzymes, thereby inhibiting vital functions, in cells such as respiration, carbon fixation, and nitrate reduction. Many plants have the ability to produce HCN; more than 2,000 species have been defined as cyanogenic.In higher plants the key enzyme to detoxify HCN is L-3-cyanoala ninsynthase (EC.4.4.1.9). In order to analyze Cyanide metabolism in relation to ethylene biosynthesis in two apple cultivar (fuji and Abbasi Mashhad) a factorial experiment was conducted in splitplotarranged based on randomized complete block design with different replication. Thequantitative and qualitative characteristics were evaluated including ethylene productionCyanide metabolism and activity of Beta–CAS in four level of temperature (-2, 0, +2, +4).Beta-CAS synthase enzyme can be assessed by measuring the sulfide that is formed duringthe reaction between HCN and L. cysteine colorimetrically. In the following study it was observed that the tissue with the highest Beta-CAS enzyme activity, has the most ethylene production level. The existence of an appropriate link between ethylene and cyanic biosynthesis and Cyanide metabolism was clear. This showed that ethylene can increase Cyanide metabolization capacity.

For the purpose of the study, the following plant species growing along roadsides in lowand high pollution density areas (BAZAR and NIAVARAN)in TEHRAN had beenselected:Lavandula officinalis Chaix. and ligustrum vulgare L. The present study shown that The air pollution caused an increase in cell membrane lipid peroxidation. The antioxidant enzymeZ activity increased to different degrees in polluted area.

Mathematical Models are helpful in designing new or improving existing dryingsystems or for the control of the drying operation. These models describe the dryingphenomena in a unified way, regardless of the controlling mechanism.In this research, Henderson and Pabis, the two-term, Lewis, Page, Modified Page, andThompson equations were used to fit moisture content variations during the drying process., temperature at four levels of 50,60,70, and 80 ºC, and also air velocity at three levels of 1, 2 and 3 m/s, and four pretreatments including hot water, %5 potassiumcarbonate, %0.4 olive oil, %0.5 sodium hydracids and no pretreatment was varied.Results showed that Moisture variations during the drying process fit to the two-termsand changed Page models well.

A suitable soil operation leads to the optimization of the soil structure, increase of soil porosity and better distribution of soil particles and finally increasing the product function. Considering the performance of wheat in the country the need for the performance of an applied research for the comparison and evaluation of common soil work methods for the cultivation of such a product seems to be necessary. This research was done in the agricultural year 2007-08 in Shahr-e-Ray region in order to compare the common soil work methods. The experiment was in the form of randomized complete block design and the compared services were: T1= Rotary tiller + leveler T2= Chisel plow + rotary tiller + leveler T3= Chisel plow + 2 times disk + leveler T4= 2 times vertical disks + leveler T5= moldboard plow one time disk + leveler T6= moldboard two times disk + leveler Parameters like: emersence percentage, soil resistance against penetration, average diameter of soil particles, the comparison of the distribution of soil particles diameter from their average, costs and comparison of services concerning the measurement time were taken into consideration and finally they were analyzed by SPSS 14 software. The results shown that there is not a significant difference between the services concerning the factor of soil resistance against penetration (at the depth of seedbed). But regarding emersence factor the service mold board plow + one time disk is in a higher level compared with other services and also concerning the soil particles diameter the service chisel + rotary tiller is in the lowest level and the service moldboard plow + 2 times disk and mold board plow + one time disk is in the highest level. The service chisel+2 times vertical disk indicated lowest distribution concerning the factor of soil particles diameter distribution from their average and on the contrary the moldboard plow + 1 time disk indicated the most distribution. The service 2 times vertical disk is the lowest level compared with other services concerning the time consumed and the cost in hectare.

To examine the effects of plant densities and sowing pattern on yield and agronomical characteristics of corn Hybrid S.C704, a field experiment was conducted in 2004 and 200 at Agricultural Research Center of Gorgan. This experiment was laid out in a randomized complete block design arranged in a split plot with four replications for two years (2004- 2005). Plant densities (D1=65000, D2=75000, D3= 85000 and D4=95000) were as main plot and sowing patterns (P1= Single row, P2= double row with 15 cm space and P3= double row with 20 cm space) were as subplots. The result of combined analysis over two years showed that by increasing plant density, trait such as grain yield, forage yield, ear height, leaves, steam, ear and cob dry matter increased. But characters such as number of grain in ear, ear diameter, ear length, kernel weight, husk dry matter, number of kernel in row and harvest index decreased. Most characters such as grain yield, forage yield, leaves, steam, ear, ear cob dry matter, total kernel per ear, ear diameter, ear length, kernel weight and number of kernel per row were increased by changing of planting pattern from single row to double row. Plant density and planting pattern interaction effect were significant at 1% level in grain yield and forage and 15 centimeter double row, 85000 plant density traits with 14170 kg ha-1 produced the highest grain yield. The highest biomass (23330 kg ha) was produced on 15-centimeter double, 95000 plant density trait treatment. Also kernelweight, number of grain in row, harvest index, ear high, ear length, leaf, stem, ear, cob and husk dry weight also significant at 1% level. The difference in number of grain in ear, husk dry weight, ear diameter, number of row grain in ear, was significant at 5% level. It was concluded that by using double planting pattern, the inter plant competition was decreased and we could get high yield.