Effect of drought stress induced by polyethylene glycol on germination and morphological properties of fennel and ajowan

Despite the importance of drought stresses in the early stages of plant growth and establishment, it has usually been neglected as a selection criterion in breeding programs. Therefore, an experiment was carried out at Zabol University Research Laboratory in a factorial experiment, based on randomized complete block design with three replications, in 2013. Experimental factors were six osmotic stress conditions (control, -1.5, -1.9, -3.5, -4.8 and -6.5 bar) and two genotypes, fennel and ajowan. The interaction of genotype and drought stress treatments was significant at the 1% probability level for all studied traits, except for seedling dry weight that was significant at the 5% probability level. Fennel than ajowan for germination percentage, speed of germination, seedling length, seedling dry weight and seedling fresh weight had greater values and ajowan than fenel had greater mean germination period. The greatest and lowest values of attribute, except for the mean of germination period (in the -6.5 bar osmotic stress and conrol, respectively), were obtained in the absence of stress (control) and the -6.5 bar osmotic stress treatment, respectively. Osmotic stress and genotype interaction showed that the highest amount of germination percentage (94.67), root length (7.10 mm), seedling length (10.36 mm), seedling dry and fresh weight (0.64 and 0.0320 gr) was achieved in the absence of stress (control) for fennel and for seed germination rate (10.31) in ajowan genotype. The highest mean germination period (9.81) was achieved for ajowan in -6.5 bar osmotic stress. Generally, fennel than ajowan had higher ability to germinate in the osmotic stress. Seed germination percentage seems to be the most important traits related to germination.