Iranian Journal of Seed Research

An experiment was conducted to investigate the effects of jasmonic and humic acids on some seed germination characteristics of Roselle under the salt stress condition in a factorial experiment, adopting a completely randomized design with three replications. Treatments included four different levels of salinity stresses: 0, 70, 140 and 210 mM; four levels of Jasmonic Acid: 0, 50, 150 and 200 mM and three levels of humic acid: 0, 40 and 80 mM. The results showed that the effect of salinity on all the traits studied was significant except the ratio of the length of root and shoot. With an increase in salinity stress condition from 70 to 210 mM, there were 39% decrease in germination percentage, 55% in germination rate, 45% in fresh and dry weight, 30% in root length, 42% in shoot length, 37% in seedling length, 67% in longitudinal index and 61% in the weighted power, as compared with the control. However, the longitudinal power index increased. In addition, the use of jasmonic acid and humic acids had a significant effect on the traits studied. The interaction of the salt and hormones had a significant impact on plant fresh and dry weight, the length of the root, germination percentage, power weight index and average time needed for 50 percent germination. Given that the highest rate of root length and plant fresh and dry weight belonged to the interaction of humic and jasmonic acid in the absence of salinity, that in the presence of humic acid (with 80 mM concentration), Rosselle can bear salinity up to 140 mM and maintain stamina root length and that the germination rate of Rosselle increases by adding jasmonic acid up to 200 mM,  one can conclude that the interaction of jasmonic and humic acids not only improves germination rate, but it also contributes to root length because, with an increase in root length, Rosselle can bear water stress conditions.

Highlights:

1.  Jasmonic acid and humic acid increase the Rosselle germination in salinity condition.
2. Jasmonic acid and humic acid increase Rosselle the root length in salinity condition.

Extended Abstract
Introduction: Catharanthus roseus is regarded as a medicinal ornamental plant. This plant has anti-cancer, anti-hypertensive, anti-diabetes, and antimicrobial properties. Catharanthus has a fairly long vegetative period due to its slow initial growth. The long growth period of the plant is considered one of the limitations in its cultivation on a larger scale. By using plant growth regulators such as salicylic acid (SA) in the imbibition phase and pre-treatment, an increase in seed activity and the seedling growth of many crops is observable. Also, jasmonic acid (JA) plant growth regulators play an important role in seed germination and plant growth. Regarding the long growth period of this plant, the small size of the seed, and poor establishment in the field with semi-heavy and heavy textured soils, the present study aimed to evaluate the effect of seed priming with SA and JA in different concentrations and periods on improving Catharanthus roseus seed germination indices.
Materials and Methods: The studies were conducted as a factorial experiment based on a completely randomized design with three replications at the Laboratory of Seed Science and Technology of Shahed University, Tehran, in 2017. Treatments included five different concentrations of SA (0, 0.01, 0.1, 0.5, and 1 mM), concentrations of JA (0, 1, 10, and 100 µM) and five periods of time (0, 6, 12, 24, and 48 hours). At the end of the experiment (10 days) traits such as germination percentage, germination rate, mean germination time, mean daily germination, germination value, seed length vigor index, seed weight vigor index, seedling dry weight, shoot dry weight, radicle dry weight, radicle length, shoot length, and seedling length were measured.
Results: The results indicated that the effect SA, JA, and time were significant on germination percentage, germination speed, mean germination time, mean daily germination, germination value, seedling length, seedling length vigor index, seedling weight vigor index, and radicle dry weight. The best times for pre-treatment with SA were 24 and 48 hours. Among the applied concentrations of SA, 0.5 and 1 mM concentrations showed the best results. Also, the best time and concentration for pre-treatment with JA were 12 and 24 hours and 10 µM.
Conclusions: The results of this study showed that using SA and JA for seed priming improved seed germination components. In addition to the pre-treatment concentrations of SA and JA, the duration of seed contact with growth regulators is important. It was observed that there was a significant difference among the different priming times, therefore, it can be stated that seed pre-treatment time is one of the important factors of seed priming, and the determination of proper priming time prevented the negative effect of pretreatment on germination and seedling growth in primed seeds.

Highlights:
1- The optimum concentrations of salicylic acid and the priming time of the seed were determined.
2- The appropriate concentrations of jasmonic acid and the optimum time for pretreatment of seed were determined.
3- The effect of growth regulators of salicylic acid and jasmonic acid on seed germination indices was evaluated.

1. The effect of priming Catharanthus roseus seeds with salicylic acid and jasmonic acid phytohormones on the germination characteristics of seeds under drought stress was investigated.
2. Priming Catharanthus roseus seeds with salicylic acid improved the germination percentage and characteristics of seeds under drought stress.