Effect of seed priming on germination and seedling growth of two medicinal plants under salinity

Priming is one of the seed enhancement methods that might be resulted in increasing seed performance (germination and emergence) under stress conditions such as salinity, temperature and drought stress. The objective of this research was to evaluate the effect of different priming types on seed germination of two medicinal plants including pot marigold (Calendula officinalis) and sweet fennel (Foeniculum vulgare) under salinity stress. Treatments were combinations of 5 levels of salinity stress (0, 2.5, 5, 7.5 and 10 ds m-1) and 5 levels of priming (control, GA3, Manitol, NaCl and distilled water) with 3 replications. Seeds of pot marigold and sweet fennel were primed for 24 h at 25°C. Results indicated that with increasing salinity, germination traits such as germination percent, rate and plumule length decreased, but seed priming with GA3 and NaCl showed lower decrease. In all of the salinity levels, primed seeds (except manitol) possessed more germination rate and plumule length than control. The highest radicle fresh and dry weight in pot marigold was seen at 7.5 ds m-1 salinity stress level. It seems that higher germination rate in pot marigold shows higher tolerance to salinity than sweet fennel. Priming with NaCl and GA3 caused an increase in germination percent of pot marigold and sweet fennel in various range of salinity, but in lower salinity levels percent of germination was higher than upper ones. The result of this experiment is consistent with the hypothesis that under undesirable conditions such as salinity stress, priming with GA3 and NaCl can prepare a suitable metabolic reaction in seeds and can improve seed germination performance and seedling establishment.