d. mazaheri

Intercropping is a beneficial farming system to intensify and sustain farm productivity. In order to evaluate forage production of maize and seed yield of bean in maize/bean (maize var 704 and bean var Goli) intercropping، a field experiment was conducted at Research Farm، Faculty of Agricultural Sciences and Engineering، Tehran University during 2006. Sowing dates of plants with three levels، simultaneous sowing for both plants، 20 day delay in sowing of bean and 20 day delay in sowing of maize were arranged in main plots. The five planting ratios (100/0)، (66. 7/33. 3)، (50/50)، (33. 3/66. 7) and (0/100) were the percentage of bean/maize arranged in subplots. Results showed that the bean seed yield / plant and bean pot number / plant were affected by interaction of sowing date and planting pattern. Delay cropping of bean in maize under planting ratio of 66. 7/33. 3 of bean/maize produced the highest dry weight of maize among intercropping treatment. Pure maize had the highest plant height and produced maximum dry weight /ha. The highest pod number per plant، yield per plant and hectare، and the lowest seed number per pod were observed in pure bean.

Seed dormancy has a critical role in ecological adaptation of wild plant species such as Hordeum spontaneum، a wild relative of barley. In this study، 192 ecotypes of Hordeum spontaneum maintained in National Plant Gene Bank of Iran (NPGBI) originating from different climatic zones of the country were evaluated. Morphological، phenological and physiological traits were recorded in the field. After harvest، the seeds were kept at 5°C for six months then were evaluated for seed dormancy. Evaluation of seed dormancy in different ecotypes of wild barley indicated that، seed dormancy was significantly higher in ecotypes of desert and cold desert climates (77. 6% and 83. 7% respectively) compared to ecotypes originating from cold steppe climates (45. 6%). The germination index was higher in cold steppe ecotypes (2. 08) than ecolypes of other climates. Correlation of seed dormancy and some qualitative traits such as glum color، grain color and awn color was significant. In this study the seed dormancy was higher in ecotypes with darker color glum، grain and awn.

In order to study the effect of water stress on yield and yield components of bread wheat and determine the critical developmental stages under stress conditions, a field experiment was conducted in Torogh Agricultural Research Station (Mashhad, Iran) in 2000/01 and 2001/02 cropping seasons, using a split plot design based on a randomized complete block design with 3 replications. Main plots were assigned to 7 levels of water stress treatments D1, full irrigation D2, cessation of watering from one leaf stage to floral initiation, and in other treatments, cessation of watering under rain shelter D3, one leaf stage to floral initiation D4, floral initiation stage to early stem elongation D5, early stem elongation stage to emegence of flag leaf D6, emegence of flage leaf stage to anthesis D7, anthesis stage to late grain filling (soft dough). Sub-plots were assigned to four bread wheat cultivars: Roshan, Ghods, Marvdasht and Chamran. Results of combined analysis of variance showed, biological yield, grain yield, yield components, harvest index and other traits were significantly affected by water stress treatments. Under D5, D6 and D7 treatments, grain yield decreased compared to D1 by 36.7, 22.8 and 45.6%, respectively. There were also significant differences between genotypes for yield and yield components. Significant correlation coefficients were found between grain yield and number of spike per m2,number of grains per spike, harvest index, spike weight at anthesis and seed set percentage. Under water stress conditions, grain yield was more affected by number of grain per unit area. Results showed, susceptibility of developmental stages of bread wheat to water stress were different. Exposing to water stress in each developmental stages, lead to decrease in yield. Grain filling (D7) and stem elongation (D5) stages were the most critical stages under water stress conditions. The effect of water stress in early pre-anthesis (D6) and tillering (D3) stages was also considerable.

Physiological factors that control the growth of wheat grains are not well known. To evaluate the grain weight potentials and post-flowering source limitation, this study was carried out in climatically conditions of Neyriz in 1995 growing season. The design of the experiment was split plot with four replications. The main plots included four planting dates (6th Nov., 22nd Nov., 7th Dec. and 22nd Dec.), and the sub plots included three wheat cultivars (Roshan, Falat and Ghods). Assimilate increase for grain growth was done through decreasing the number of spiklets. In each spike, four spike lets with numbers 3, 6, 9 and 12 were kept and others were left out. The results indicated that source limitation increased with delaying the planting practice, in such a manner that the grains produced in the delayed planting date faced with a limitation of about 44.2% whereas the limitation for the first planting date was 4.8%. On the other hand, comparison among cultivars showed that source limitation average for Roshan cultivar was less than Falat and Ghods. The source limitations for above-mentioned cultivars were 13.6%,20.6% and 22.9%, respectively.