Effects of gibberellic acid, kinetin and cold stratification on seed germination of Pyrus pyraster Burgsd. and Malus dasyphylla Borkh. species

Germination tests were carried out to determine the best treatment to be used in order to overcome dormancy and maximize the germination of P. pyraster and M. dasyphylla seeds. In both species, the effects of gibberellic acid (GA3), kinetin (6-Furfurylaminopurine), cold stratification, a combination of GA3 with cold stratification and a combination of kinetin with cold stratification on seeds germination were investigated. Seeds of both species were treated with solutions of GA3 or kinetin for 30 hours and were, subsequently, cold stratified at 3 - 5ºC for 0, 1, 2 and 3 months. The concentrations of GA3 and kinetin solutions were 500, 1000 and 2000ppm. In addition, seeds from each species, which were not treated with GA3 or kinetin (control), were subjected only to cold stratification for 0, 1, 2 and 3 months. Non-stratified P. pyraster seeds, despite having been treated with GA3 or kinetin solutions, exhibited very low germination percentages. In P. pyraster, germination percentages of control seeds subjected to cold stratification for 2 and 3 months were higher (p<0.05) than those of control seeds subjected to cold stratification only for 1 month. In each period of cold stratification, there were no significant differences (p>0.05) in germination percentages between control seeds and seeds treated with GA3 and kinetin solutions. In M. dasyphylla, GA3 or kinetin application did not improve the germination of non-stratified or onemonth stratified seeds. In control seeds and seeds treated with GA3 or kinetin, an increase in the period of cold stratification, increased germination percentages significantly (p<0.05). In each period of cold stratification, there were no significant differences (p>0.05) in germination percentages between control seeds and seeds treated with GA3 and kinetin solutions except for one case. After 2 months of cold stratification, the germination percentage of control seeds was higher (p<0.05) than the germination percentages of the seeds which had been treated with 500 and 2000ppm kinetin. In both species, low values of mean germination time were observed. The results demonstrated that the optimum germination percentages of P. pyraster and M. dasyphylla seeds (control) were obtained after a 2- or 3-month and a 3-month cold stratification period, respectively. In both species, the application of GA3 or kinetin did not replace or shorten the required cold stratification period.