Stimulation of germination in dormant seeds of Juniperus polycarpos by stratification and hormone treatments
2016
Dormancy in Juniperus polycarpos (K. Koch) seeds is a major hurdle for production of the desired quantity of seedlings in nurseries for restoration purpose. Thus, the aim of this study was to develop an optimal dormancy breaking treatment and subsequent stimulation of germination. The treatments applied were cold stratification at 1 °C for 4, 8, 12, and 16 weeks; warm stratification at 20 °C for 4, 8, 12, and 16 weeks followed by 12 weeks of cold stratification; exogenous application of 250, 500, and 1000 ppm gibberellic acid (GA3) and 6-Benzylamino purine (BAP); and a combination of 500 ppm hormones and cold stratification. The results show significant differences in germination between cold and warm-cold stratification, length of stratification and their interaction (p < 0.01). Warm stratification for 16 weeks followed by 12 weeks of cold stratification induced 72 % of the seeds to germination in 12 days compared with 16-week cold-stratification alone (42 %) and the control (8 %). Exogenous application of GA3 and BAP alone or in combination with cold stratification resulted in less than 50 % germination though significantly (p < 0.01) higher than the control. Apparently, the hormone treatments alone or in combination with cold stratification are not effective in completely breaking dormancy and stimulation of germination. The findings suggest that J. polycarpos seeds may possess intermediate simple morpho-physiological dormancy, which could be an adaptive mechanism for relatively warmer autumn temperature during seed maturation and the subsequent cold winter temperature under natural conditions.
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