The Effect of Apple Seed Stratification with Growth Regulators on Breaking the Dormancy of Seeds, the Growth of Seedlings and Chlorophyll Fluorescence

The aim of the study was to shorten the period of breaking dormancy in apple seeds and to improve the growth of the seedlings of ‘Gold Milenium’, ‘Ligol’ and ‘Szampion’. The whole seeds were removed from fruits directly after the harvest and were subjected to stratification (3 °C for 90 days in darkness) in distilled water or an aqueous solutions of 500 mM salicylic acid (SA), 10⁻³ M jasmonic acid (JA), gibberellin A₃ (GA₃) and 6-benzylaminopurine (BAP) at 250 mg·dm⁻³ and 100 mg·dm⁻³, respectively. Growth regulators were applied separately or in a mixture containing SA, JA, GA₃ and BAP. The germinability and seed germination rate, seedlings growth, chlorophyll content index and the maximum quantum efficiency of Photosystem II (Fv/Fm) were investigated. The obtained results revealed that stratification in water positively affected the dormancy removal in ‘Gold Milenium’, ‘Ligol’ and ‘Szampion’ seeds. Application of SA, GA₃, BAP, JA during seed stratification additionally stimulated the seeds’ germination rate as well as the growth of seedlings, index of chlorophyll content and maximum PSII efficiency (Fv/Fm). The most pronounced results were obtained after the seed stratification in GA₃ alone or in a mixture containing SA, GA₃, BAP and JA. Due to such a treatment, the germination of ‘Ligol’ seeds increased by 40% and they germinated faster in comparison to the control seeds. Such treatments also promoted the growth of seedlings, chlorophyll content and maximum quantum efficiency of Photosystem II (Fv/Fm). The present study indicates that the application of GA₃ or the mixture of SA, GA₃, BAP and JA during the stratification of seeds is an effective method to increase and accelerate the germination of seeds and juvenile seedlings’ growth in order to shorten the apple breeding cycle. Further studies are needed to optimize the appropriate concentration of growth regulators applied simultaneously during seeds stratification.