Morphophysiological dormancy, germination, and cryopreservation in Aristolochia contorta seeds

Abstract

Background and aims – Aristolochia contorta is a valuable medicinal plant, a relict of the Tertiary flora. Little is known about the germination biology of Aristolochia. The specific objectives of the present study were to (1) determine the type of dormancy in seeds of A. contorta, (2) describe the embryo development, and (3) explore the influence of deep freezing of the seeds in liquid nitrogen on their germinability.Methods – Seeds were germinated in Petri dishes in sand previously sterilised at high temperature; germination experiments were carried out at 27±2°C under natural light. All measurements of seeds and embryos were done using light microscopy (LM). For cryopreservation, fresh seeds were placed in aluminium foil bags, immersed into liquid nitrogen (-196°С), and stored for twelve months.Key results – The seeds of Aristolochia contorta have non-deep simple morphophysiological dormancy. A variety of embryo forms were revealed for Aristolochia species for the first time. Two cases of polyembryony were noted in A. contorta. The seeds of A. contorta are resistant to cryopreservation in liquid nitrogen.Conclusions – High variability in dormancy depth and the extended germination period of A. contorta seeds can be considered as adaptive strategies for survival in unfavourable conditions and renewal of germination under optimal conditions. Cryopreservation helped maintain the viability of A. contorta seeds but did not lead to the breaking of the dormancy; hence, for successful germination, it is necessary to use methods of breaking dormancy after freezing.