growth analysis and evaluation of change in simple non- structural carbohydrates during bulb formation of onion cultivars in karaj climatic conditions

abstract an experiment was conducted to study growth analysis and evaluation of change in simple non- structural carbohydrates (sucrose, glucose and fructose) during bulb formation of ghermez azarshahr , zargan, safid naishaboor and safid qom cultivars in randomized complete block design containing three replications. seeds were sown in nursery in early february and seedlings were transplanted in early may. during initiation of bulbing carbohydrates accumulated in leaf bases. before and after bulb formation (about 20 days after bulb formation) the most simple non-structural carbohydrates content was found in safid qom cultivar. the maximum and minimum increasing percent of simple non- structural carbohydrates components belong to glucose and sucrose respectively. the results of growth analysis indicated that the period of slow growth had been about 75 days after emergence (for all studied cultivars) and then the period of rapid growth of leaf has begun. the bulb growth rate of zargan cultivar during the most parts of bulb development stage was higher than other culitivars, due to this reason and earliest date of bulbing, yield of mentioned cultivar was higher as compared with other cultivars. a high significant positive correlation ( r = 48% ) was found between relative growth rate and net assimilation rate at 1% level. zargan cultivar produced the highest total and marketable yield, so that mentioned cultivar is recommended for karaj region.