Ethanol – germination regulator of the Siberian mountain ash (Sorbus sibirica) seeds

Intact rowan seeds are characterized by deep physiological dormancy due to the physiological mechanism of germination inhibition, which is regulated by the balance of phytohormones. The depth of dormancy depends on individual characteristics, pollinator plant, storage conditions and other factors. Long cold stratification at low positive temperatures is necessary to overcome dormancy. Combination of such stratification with treatment with exogenous phytoregulators (kinetin, gibberellic acid) allows reducing the duration of pre-sowing treatment, but does not eliminate the diversity of seeds by this indicator. When experimenting with seeds in the laboratory, in addition to stimulating germination, methods of retarding germination must be employed to fine-tune it. It was revealed that ethyl alcohol is an effective regulator of Siberian mountain ash (Sorbus sibirica Hedl.) seed germination. Ethanol is a natural metabolite of plants and is involved in the regulation of ethylene signaling pathways, and can compete for hydrogen bonding sites on the surface of lipids and proteins. Fully matured seeds collected in October, stored at room temperature for 150 days, were used for the experiment. The seeds were stratified at 1-4 °C in Petri dishes. The effect of ethanol at concentrations of 1–10% in 1% increments was investigated. A pronounced inhibitory effect of ethyl alcohol on the germination of Siberian mountain ash seeds at concentrations above 2% was revealed. When the seeds were cold stratified (3 ºC) on a substrate containing 5% ethanol, complete inhibition of germination was observed after 150 days of stratification compared to the control, where about 50% of the seeds germinated; about 20% of the seeds germinated at a concentration of 2%. The seeds remained viable and after increasing the duration of stratification to 200 days on substrate containing 5% alcohol germination was 21%, and it was 43% compared to the control where 65% of the seeds germinated containing 2%. Seed treatment with ethanol can be used as an alternative economical technique to regulate germination of Siberian mountain ash seeds.