Journal of Agricultural Science and Technology
Volume:6 Issue: 1, Apr 2004

Field experiment was conducted at the agricultural experiment station of Shiraz University at Kushkak in 1996 to quantify the competitive ability of pinto beans (Phaselus vulgaris L. var. Daneshjou) with a naturally occurring population of weeds. An attempt was made to increase the competitive ability of the plants by altering row and plant spacings. An uncontrolled population of weeds reduced pinto bean yields by 75%. The ability of plants to reduce weed dry weight was further enhanced in medium and narrow rows compared to wide rows. Row and plant spacing combinations which maximized leaf area index when grown under weedy conditions also had significantly less weed dry weight. However, row and plant spacings did not reduce weed density. A significant negative correlation was observed between weed dry weight with leaf area index and final yield of pinto bean. For each kg ha-1 increase in weed dry weight, the corresponding pinto bean yield loss averaged 260 g ha-1. Season-long weed competition significantly reduced total number of pods per plant, number of seed per plant, and 100-seed weight.

There are two reasons for measuring the mechanical properties of cereal grains. First, the possibility of grain classification based on texture and, second, to obtain information for modification in the design of post-harvest machinery. In both cases, the objectives will be the reduction of qualitative and/or quantitative losses of grain. In this research, eight different parameters obtainable from the force-deformation curves of wheat kernels under compression were determined. The most important of these included: the apparent modulus of elasticity, maximum compressive contact stress and maximum load at rupture. Other grain characteristics such as the dimensions of single wheat kernels and the particle size index of bulk samples for five varieties of wheat were measured. By performing 200 uniaxial compression tests on intact wheat kernels (from soft to very hard varieties), the values of modulus of elasticity ranging from 486 to 1631 MPa were determined based on measurements according to the Hertz theory. Results indicated a simple linear relationship between grain hardness and mechanical properties, such as modulus of elasticity and deformation at the linear limit on the force-deformation curve, and physical attributes, such as grain mass and major diameter. Grain orientation had no significant effect on the dependent variables. Moisture content had a very significant effect on mechanical properties. From the statistical analysis of the data (ANOVA and DMRT), it was found that it is possible to distinguish between soft and hard wheat kernels based on different parameters obtainable from the force-deformation curve. Hence, any one of these parameters may be used as a suitable indicator for grain hardness determination.

Eighteen crossbred Swifter (Flemish ♀ X Texel ♂) male lambs, born in March 1997 and weaned at the age of approximately 3 months, were used to quantify effects of feed quality restriction and realimentation on changes in energy and nitrogen metabolism. The ration consisted of grass straw (17 MJ of GE and 46 g CP per kg DM) on an ad libitum basis and 35 g.kg-.75d-1 mixed concentrates (16.5 MJ of GE and 173 g CP per kg DM). At the age of approximately 3.5 months, the animals were randomly divided into six blocks, based on live weight, according to a randomized complete block design. Within each block, the animals were randomly assigned to two restricted treatments (R1 and R2) and a control treatment. Treatments R1 and R2 were subjected to feed quality restriction by withholding concentrate for 3 and 4.5 months, respectively. A modified linear model was developed to study the effects of restriction and realimentation. The comparison between treatments was made by analyzing the data of R1 and R2 animals as deviations from the control animal in each block. During the restriction period, restricted animals lost weight and showed a negative EB and NB, whereas their intake from low-quality roughage significantly (P < 0.001) increased. After realimentation, the R1 and R2 animals grew significantly (P < 0.001) faster than the C animals. The realimented animals persisted in ingesting more (P < 0.001) low-quality roughage and their EB and NB were greater (P < 0.001) than those of C animals. The R2 animals needed a longer period of realimentation because of a longer period of restriction. The expression of compensatory growth was mainly related to a sustained higher (P < 0.001) grass straw (low-quality roughage) intake during realimentation periods, and greater (P < 0.001) efficiency of metabolizable energy intake. The maintenance requirement of realimented animals was lower (P < 0.001) only during the initial stages of realimentation compared with controls.

To study the capabilities of remotely sensed data in discriminating land cover types and geomorphologic features of desert, the southeast of Lut Desert was selected. In this study, seven bands of Landsat Thematic Mapper (TM), data and other sources of information such as topographic maps (1:50,000), aerial photos (1:20,000) and field data were used. The visual image interpretation was performed based on photomorphic unit analysis and interpretation keys. To classify the images, 10 training classes were used for maximum likelihood classification algorithm. Then the classified images were assessed with the test areas and the overall accuracy was about 92 percent. Based on the obtained results it may be concluded that Landsat TM thermal and reflective bands could be useful for studying Lut Desert conditions especially in the Yardang and sand dune regions. From the results obtained we may also conclude that such a hyper arid climatic and bare land are suitable conditions for a better understanding of the behavior of TM wavebands on different sur-faces and soil conditions.

In the absence of dwarfing rootstocks for apricot (Prunus armeniaca L.), techniques that reduce vegetative growth while enhancing fruit quality and yield are important in the orchard management system. Four year old mature apricot trees cultivars Nasiri, 35Shahroodi, Jahangiri, Shahroodi and Noori on apricot seedling rootstocks, planted at a density of 1250 trees ha-1 and grown at Tarbiat Modarres University (TMU) orchard were used. The effect of soil applied paclobutrazol (0.5 and 2 g tree-1 a.i.) on apricot trees was studied over three years period during 1998-2000 seasons. Treatment effects on vegetative and reproductive growth characteristics and the leaf nutrient status of the apricot trees were determined. Results indicated that paclobutrazol (PBZ) significantly reduced vegetative growth during the experiment. The total pruning dry weight, shoot growth and trunk cross sectional area (TCSA) of treated trees were lower than those of the controls. Although, results showed that fruit load, crop density and total soluble solids (TSS) of fruits were not affected by applied treatments compared with the control. In addition, PBZ decreased nitrogen (N) concentration, but, phosphorus (P), potassium (K) and calcium (Ca) concentrations were not affected by the treatments. Chemical name of PBZ is: (2RS, 3RS)-1- (4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)pentan-3-ol.

In this research, methanolic extraction of Salvia leriifolia leaves produced a higher yield and antioxidative activity than other organic solvents (ethanol, acetone, chloroform, n-hexane). ‏The methanolic extract was reserved about 24 hours in the refrigerator and its precipitates were then separated. The extract was separated into 12 fractions by thin-layer chromatography (TLC). The highest yields were found in fractions with Rf values of 0.29, 0.54, 0.11 and 0.38 at 16.24%, 12.48%, 8.81% and 7.60%, respectively. All fractions and also whole methanolic extract and precipitates of methanolic extract had more antioxidative activity than the control based on the thiocyanate method. Whole methanolic extract, precipitates of methanolic extract and most separated fractions showed more antioxidative activity than a–tocopherol. The fraction with Rf value of 0.29 at 16.24% yield and 85.61% antioxidative activity of synthetic antioxidant BHT based on thiocyanat method was chosen as the fraction with the highest yield and the highest antioxidative activity.

Expression analysis was carried out to characterise the level and time of expression of two senescence related cDNAs, LSC650 and LSC54, in Brassica napus and Arabidopsis thaliana. The extent of DNA sequence similarity showed that the LSC650 gene may encode the catalase homologous to Cat3 in Arabidopsis thaliana the role of which is to scavenge H2O2. Also, LSC54 gene encodes a metallothionein protein that may detoxify metal ions in plant cells. Plant leaves were characterised at different developmental stages by biochemical analysis, including chlorophyll and protein assays. Northern analysis revealed strong levels of LSC650 and LSC54 expression in senescent leaves and lower levels in mature green leaves, but very weak or no expression in young leaves in B. napus. The transcription of genes, LSC650 and LSC54, was almost at the same level with few changes between maturity and senescence in leaves of Arabidopsis at different plant growth phases, being due to a possible unknown stress. The results indicate that both genes studied may act as antioxidants, and have a role in scavenging active oxygen species (AOS) caused by catabolism of macromolecules during senescence.

In this investigation levels of calcium were measured on the flag leaves of the susceptible spring wheat cultivar Thatcher and its near-isogenic line that has Yr-18 gene-mediated durable adult-plant resistance (APR). The results showed that crystals of various shapes were frequently present on the infected leaf areas in the spring wheat that has the APR to stripe rust. Crystals were characterized with an energy-dispersive X-ray microanalayser in conjunction with scanning electron microscopy (SEM). More calcium was mobilized into infected areas of the resistance line than into the susceptible genotype. The level of calcium in the non-infected areas of both resistant and susceptible hosts and on the infected areas of the susceptible genotype were nearly the same. The results indicated that calcium mobilization in the resistant near isogenic line upon infection with P. striiformis correlated with the elicitation of a defense response conditioned by the Yr-18 gene. This is the first report on the mobilization of calcium in a cereal-rust pathosystem as part of a resistance response.