Effects of stratification and pre-treatment with gibberellic acid on seed germination of two Carpinus species

Author： Pipinis E. Milios E. Kiamos N. Mavrokordopoulou O. Smiris P.

Publisher： International Seed Testing Association

ISSN： 1819-5717

Source： Seed Science and Technology, Vol.40, Iss.1, 2012-04, pp. : 21-31

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Abstract

The aim of this study was to determine the best treatment to use to overcome dormancy and to maximize germination of Carpinus betulus and C. orientalis seeds. In both species the effect of warm stratification (WS), cold stratification (CS) and gibberellic acid (GA₃) application on seed germination was investigated. Seeds of both species were subjected to WS (20-25°C) for 0, 1 and 2 months and then cold stratified at 3-5°C for 0, 1, 2, 3 or 4 months (1st experiment) or treated with 500, 1000 or 2000ppm GA₃ for 30 hours and then cold stratified at 3-5°C for 0, 1, 2, 3 and 4 months (2nd experiment). In the first experiment, in both species, no germination was observed in seeds subjected to only 1 or 2 months of WS and up to 2 months CS alone resulted in very low seed germination. In C. betulus, the combination of WS and CS improved seed germination. Seeds given a period of 1 or 2 months of WS prior to CS, germinated to higher (P < 0.05) percentages than those subjected to only CS. In contrast, in C. orientalis seeds an increase of WS period from 1 to 2 months, prior to CS treatment (2, 3 or 4 months), significantly decreased (P < 0.05) germination percentages. Results of the second experiment showed that GA₃ application, prior to CS, was more effective in improving germination in C. betulus than C. orientalis. In C. betulus, GA₃ application entirely replaced the requirement for WS and shortened the required CS period, resulting in satisfactory germination percentages. In C. orientalis, the GA₃ treatment significantly improved germination of seeds cold stratified for 2 or 3 months, but germination percentages were significantly less (P < 0.05) than those of seeds subjected to only 4 months CS. In both species, the treatments that gave germination percentages ≥70% (in both experiments) exhibited a reduction of mean germination time (MGT) with an increase in CS period.