بررسی امکان نگهداری بذر تعدادی از گونه های جنگلی در شرایط فراسرد

Cryopreservation or storage at -196 C is a new and most important method of preserving plant species for a long period. Using cryopreservation, most of the seeds, vegetative organs, cells and pollens can be preserved for a long time. Cryogenic conditions stop much of the metabolic processes of the cells and, period of preservation dramatically increases. Seeds of the following forest and woody species were collected from different habitats: Acacia nilotica, Acacia tortilis, Acer monspesulanum, Biota orientalis, Castanea sativa, Eucalyptus microtheca, Olea europea, Pistacia vera, Pistacia atlantica, Pistacia khinjuk, Populus euphratica, Robinia pseudoacacia, Sophora mollis, Taxus baccata, Ulmus glabra, Ulmus carpinifolia and Ziziphus spina christi. Three pretreatments including Vitrification (PVS2), Desiccation and 30% Glycerol were applied before transferring the seeds into liquid nitrogen. Depends on plant species, the seeds were stored in liquid nitrogen for 1 week, 1month, 1year or 26 month. Following removal from liquid nitrogen, the seeds subjected to heat shock (42 C) and germinated under laboratory conditions. Different attributes including seed germination percentage, root and shoot lengths, germination speed, root/shoot length ratio and seed vigor index (VI) were recorded and statistically analyzed. Second sample of the same seeds were sown in pots and grown under greenhouse conditions. Seeds of three species including: Castanea sativa, Olea europea and Taxus baccata, did not show positive results. In this regard, seeds of the Castanea sativa did not tolerate cryopreservation (-196 C) and perished after removal from liquid nitrogen. Olea europea seeds did not germinate and, Taxus baccata seeds had a poor germination. In the rest of species, high seed germination percentage and other attributes, either in laboratory or greenhouse conditions revealed the cryotolerance of the seeds. In greenhouse experiments, plants developed from cryogenic seeds grew normally and did not show any abnormality compared to those of the control plants. In general, the results of the present study indicated that the cryopreservation (-196 C) technology can be used for long-term preservation of most of the forest species' seeds. However for cryopreservation of recalcitrant and non-germinating seeds, alternative approaches such as apical and axillary buds, cells, meristems, embryo axes etc., should be applied. Keywords: Cropreservation, PVS2, Plant Germ Plasm, Seed Cryopreservation, Desiccation, 30% Glycerol, Vitrification, Forest Plant Seeds, Recalcitrant Seed. Acacia nilotica, Acacia tortilis, Acer monspesulanum, Biota orientalis, Castanea sativa, Eucalyptus microtheca, Olea europea, Pistacia vera, Pistacia atlantica, Pistacia khinjuk, Populus euphratica, Robinia pseudoacacia, Sophora mollis, Taxus baccata, Ulmus glabra, Ulmus carpinifolia and Ziziphus spina christi.