ویژگی‌های فیزیولوژیک و عملکرد دانه گندم زمستانه در پاسخ به تراکم بوته و تاریخ کاشت

The physiological characteristics of winter wheat(cv. Shiraz) were evaluated in a 2-yrs field study by using a spilit plot design with four replications, at the experimental farm of Shiraz University, College of Agriculture located at Badjgah. Main plots consisted of three sowing dates (November 6th, December 6th and January 5th) and four planting densities (150, 250, 350 and 450 plants/m2) were assigned as sub plots. The results indicated that delay in sowing was associated with a significant reduction in the grain yield. So that the grain yield in sowing date of January 5th was significantly less than it in sowing dates of November 6th and December 6th. Moreover with delay in sowing date the developmental rate of wheat was enhanced and plants reached maturity more rapidly. The trend of the leaf area index changes and the dry weight of the plants were under the effect of experimental treatments, leaf area index was found to be greater at the higher densities and early planting date. Number of stems per m2 were decreased with delay in the sowing date, although at the higher densities, the number of stems per m2 was greater, despite severe tiller death observed at these densities. The study of trend of dry weight changes during the season indicated that biomass was greater at higher densities and earlier sowings, which resulted in earlier ground cover and higher amount of radiation interception. In conclusion, the results of the present investigation revealed that to achieve a reasonable grain yield, the 6th of December and 250 plants per m2 were the best sowing date and planting density for wheat (cv. Shiraz) under similar agro climatic conditions with the present investigation.