جستجوی مقالات مرتبط با کلیدواژه "شرایط نامساعد" در نشریات گروه "زراعت"

In order to determine, source of grain yield limitation under different enviromental conditions, as well as indentifying the rate of restrication caused by terminal heat stress on development and growth of wheat, this research was conducted with twenty wheat genotypes using Randomized Complete Block Design (RCBD) with three replications, in two separate experiments in two years(1998-2000). The experiments were sown in late of december and january to stimulate favoarable and unfavourable conditions, respectively. Five to seven days after anthesis flag leaf and spikelets from one side of spike were removed to stimulate, sink and source limitation respectively. Aftert harvest, source and sink restrication percentage were calculated according to the mean of remaining grains in treated spike and control (without removal of flag leaf and spikelets). Results indicated that all genotypes had not sink restrication and the contribution of flag leaf to grain dry weight was 12%. However, some genotypes showed source restrication. This restrication was estimated from 0 to 34% (mean: 12.6%) and 5.7 – 41.2% (mean:17.2%) for favourable and unfavourable conditions, respectively. Therfore, source restrication caused by exposure to terminal heat stress was greater by 6%. Likewise, results indicated that source restrication was higher in genotypes with large grain size. Grain weight had not significant effect in the determination of final yield. Reduction in grain yield must be sought in other yield components, such as grain number per spike and spikes number per sqaure meter.