Determining the threshold salinity and appropriate temperature, and their combined effects on germination of Cuminum cyminum

Document Type : Research Article

Abstract

Cumin is an important medicinal plant and its cultivation in arid and semi-arid parts of Iran which water is a serious constraint to agricultural production has a high economical feasibility. In order to determine the threshold salinity and temperature and their interaction effects on cumin germination a complete randomized experiment with factorial arrangement was performed in the laboratory. Salinity levels of 0, 2, 4, 6, 8, 10, 12, 14 and 16 dS/m using NaCl and CaCl2 with 5:1 molar ratio and temperature levels of 0, 2, 4, 6, 8, 10 and 12 degrees Celsius were considered. The regression analysis of the germination data showed that the germination percentage and rate were not changed until reaching threshold salinity (EC*), and decreased linearly afterwards. The EC* values for percentage and rate of germination were found to be 3.06 (±0.55) and 3.02 (±0.83) dS/m, respectively. The regression slopes for germination percentage and rate were found to be -4.49 (r2=0.98**) and -0.147
(r2=0.97**), respectively, which means at salinity levels higher than EC* the germination percentage decreased 4.49% and the rate of germination was lowered by 0.147 seed per day. In addition, the results showed that with increasing temperature up to 4 °C the percent and rate of germination increased. In the range of 4 to 8 °C the highest percentage and rate of germination was observed, and afterwards by increasing temperature these factors were decreased. There was no significant difference in germination characteristics between 4, 6 and 8 °C, however, there was a significant difference (P<0.05) between 0, 2 and other treatments. The analysis of interaction effects of salinity and temperature on percent and rate of germination showed to be non-linear. In all salinity levels the percentage of germination increased with increasing temperature, and reached its maximum values in the range of 4 to 10 °C. Based on the results of this research the rate of germination could tolerate a
higher threshold salinity value (> 5 dS/m) within these temperature ranges. The results of this research which was performed in laboratory provided the preliminary information on cumin germination characteristics as affected by salinity and germination. Further research in the soil medium seems to be necessary.

20.1001.1.20081472.1388.7.1.29.7

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