DEEP DRYING OF SEEDS IN RELATIONSHIP TO T HEIR PRESERVABILITY

Decrease of moisture content is an important tool for prolongation of preservability of seeds of genetic resources. In gene banks this measu re is combined with keeping the seeds at low temperature (+5 to -20 de grees C). Appropriate application of deep drying of seeds of some plan t species should allow long-term storage of seed samples without neces sary temperature regulation. Technically, the decrease of seed moistur e below 5% is attainable only by gradual sublimation of water in vacuu m. Our experiments were aimed at testing of seeds of the plant species and to choose those without biological change in drying below 5% mois ture and in them to set the influence of deep drying on seed germinati on capacity. To determine most suitable time for deep drying the follo wing times of sublimation (in hours) were used: 1, 3, 10, 14 and 18. T he time of 14 hours was found to be an optimum for achieving deep dryi ng by sublimation. The sublimation method of drying applied for 14 hou rs was then used for testing of seeds of 56 crops (botanical special o f cultural plants or their forms) of 19 families. Deep drying below 5% moisture was attained in 84% of crops. The moisture did not decrease below 5% limit only in cereal and legume seeds. The level of moisture after 14 hour deep drying achieved the following rates: 13 crops were dried to moisture ranging from 2 to 3%, 23 crops were dried to moistur e of 3 to 4%, 11 crops were dried to moisture of 4 to 5%, 3 crops drie d to moisture of 5 to 6%, 4 crops dried to moisture of 6 to 7%, 2 crop s dried to moisture of 7 and more %. The effect of deep drying on germ ination capacity was set out for 10 crops. The decrease in germination capacity ranged only from 0 to 4%. Except wheat when 4% decrease in g ermination capacity occurred, the decrease in germination capacity due to deep drying did not exceed 2%. Wheat as a representative of cereal s in all probability is not suitable for applicatiom of deep drying, a s for attaining moisture below 5%, as for more marked decrease in germ ination capacity due to deep drying. Deep drying improved preservabili ty of seed germination capacity in all crops under study compared with the partially dried seeds. Compared with the drying to 6 to 8%, germi nation capacity of rape and carrot dried down to by 2 to 5%, was highe r approximately by 10%. In association with storage temperature the fu ll harmony of deep drying with the standard one occurs only at tempera ture of -18 degrees C, at higher temperatures (+4 degrees C, +18 degre es C and +40 degrees C) positive influence of deep drying on maintaini ng higher germination capacity increases with increasing temperature. The positive impact of deep drying was most manifested at temperature of +40 degrees C and partially also at +18 degrees C. The difference b etween temperatures -18 degrees C and +4 degrees C due to deep drying was not recorded. The survey of genera in which after 14 hours of dryi ng the moisture value of seeds below 5% was achieved: Agrimonia, Alliu m, Anethum, Beta, Borago, Brassica, Calendula, Carum, Capsicum, Cichor ium, Coriandrum, Cucumis, Cucurbita, Daucus, Fagopyrum, Festuca, Helia nthus, Hypericum, Hyssopus, Inula, Lactuca, Lepidium, Lolium, Lycopers icon, Malva, Marrubium, Mellissa, Ocmium, Ononis, Origanum, Panicum, P apaver, Raphanus, Ruta, Salvia, Satureja, Silybum, Solanum, Spinacia, Tetragonia, Trifolium, Trigonella, Trisetum, Vallerianella.