EFFECTS OF HIGH TEMPERATURE AND WATER STRESS ON DORMANCY AND GERMINATION OF SORBUS SIBIRICA SEEDS

Abstract

A research was carried out into the peculiarities of dormancy and germination of Sorbus sibirica seeds with short-term interruption of cold stratification (1–3oC) by temperature and water stress (rapid drying at 25oC). To induce germination, a laboratory method for stratifying freshly isolated intact (unsaturated) seeds at 1–3oC was used. The homogeneity of the seed sample was monitored by SDS-PAGE and ISSRPCR. The seeds were stratified at 1–3oC for 45, 59, 73 and 87 days, and the stratification was interrupted by rapid drying at 25oC for 1, 3, 7 and 14 days. After drying the experiment was continued in two versions: the seeds were soaked in cold (1–3oC) water or phytohormones (48 hours in gibberellic acid (GK3) solution of 100 mg/l, then 48 hours in kinetin (K) solution of 500 mg/l). Then the seeds in all variants were re-stratified at 1–3oC for 60 days, and germinated at 25oC for 72 hours, the percentage of germination and the lengths of the roots being estimated. It was established that interruption of cold stratification by rapid drying, irrespective of the method of subsequent processing (phytohormones or water), had a strong stimulating effect on germination in Sorbus sibirica seeds. In most variants more than 90% of the seeds germinated. Earlier experiments with continuous cold stratification of intact Sorbus sibirica seeds showed that 17–19% of seeds germinated within 105 days. Changed duration of stratification before drying did not affect the percentage of germination: it remained highest in all variants. The longer stratification lasted, the greater the length of the roots was. Significant deviations in forming seedlings were observed in seeds treated with phytohormones: the roots did not practically develop; their length after 72 hours of germination was 10–20 times lesser than that in seeds treated with water. Cotyledons, on the contrary, increased significantly, and were pale green. Two-stage cold stratification with intermediate temperature and water stress makes it possible to achieve more than 90% germination of seeds without phytohormones.