Moisture Stress impacts on Growth Traits of three Populations of Black Cumin (Bunium persicum) during the First Year of its Growth

Black cumin (Bunium persicum Bioss) is a small and perennial herbaceous plant. During the first year of the growth, this plant produces only cotyledon leaves and small root that becomes to underground tuber after growth. Lack of sufficient rainfall with irregular patterns over black cumin growing areas cause drought stress during different growth periods of plant, especially during the first and the second years of plant growth when tubers do not well formed. Therefore, this study was planned to evaluate moisture stress impacts on the growth of black cumin during the first year of its growth.

In order to investigate the effect of moisture stress on black cumin, an experiment was carried out in a factorial experiment based on completely randomized design with three replications at College of Agriculture, Ferdowsi University of Mashhad during 2014. The factors were included plant population in three levels (Kuhbanan, Sirjan and Kalat) and three levels of moisture stress [100, 75 and 50% of Field Capacity (FC)].
During mid-April, seed dormancy was broken by the GA and chilling. Germinated seed were planted in pots (diameter 10 cm, height 15 cm) at a depth of 1-2 cm. Pots was irrigated at FC level for up to two weeks after seedling establishment . After that pots weighted, and if the weight decreased from FC, added water to reach the desired pot weight. At the end of the growing period (seven weeks after drought stress in mid-June) all plants in each pot were harvested. Plant height, root length, shoot and root dry weight, tuber diameter and tubbering percentage were measured. Samples of shoot and root were placed in oven at 75°c for 24 hours and then their dry weight were measured by a digital scale with accuracy of 0.001 g.
Statistical analysis was performed by using the software MSTATC and the means were compared by using the LSD test.

The results showed that the differences between populations for all traits were significant, except for root length and shoot/root dry weight ratio,. The effects of moisture stress and population and their interactions were significant for all traits. Plants in all populations, at 50% FC were killed due to drought stress. Kalat population at 75% FC had the maximum length of roots and shoots. Also, at 75% FC Sirjan population had the most reduction in shoot dry weight. At 75% FC Kuhbanan and Sirjan populations had 15% reduction in height while this reduction in Kalat population was 24%. Root dry weight at 75% FC in all populations was less than 100% of FC. In all population the tuber was formed only at 100% FC and plants grown at 75% FC did not produce tubers.

Results demonstrated that reducing the soil moisture from 100% FC had negative impacts on the growth traits of black cumin. Since the black cumin is a perennial plant, it would be useful to study the effects of moisture stress during different years