SEED CHARACTERIZATION FOR PROPAGATION AND CONSERVATION OF OXERA PULCHELLA SUBSP GRANDIFLORA (DUBARD) DE KOK, A NEW CALEDONIAN ORNAMENTAL ENDEMIC

摘要

The Royal Creeper, Oxera pulchella subsp. grandiflora (Dubard) de Kok (Lamiaceae) is a New Caledonian threatened endemic taxon with high ornamental potential. Propagation by cuttings has till now been the main propagation method for ornamental uses. A characterization of the seed biology is required in order to promote a better development of O. pulchella subsp. grandifiora ornamental potential, through maintaining its genetic diversity and its conservation. A seed analysis was conducted to define seed structure, germination conditions, dormancy, and desiccation tolerance. Seeds were shown to be of exalbuminous type with a permeable endocarp. Seeds displayed a non-deep physiological dormancy. When desiccated by equilibration in nine atmospheres with controlled relative humidity, seeds desiccated to lower water content (2.8 +/- 0.5% of fresh weight) displayed a germination rate of 63 +/- 13% compared to non-desiccated control, indicating that Oxera pulchella subsp. grandiflora seeds were desiccation-tolerant. Protocols combining seed desiccation and low temperatures storage revealed that seeds desiccated in an atmosphere with a relative humidity of 45% and conserved at 4 degrees C were viable after one-year period storage, with a germination rate of 50%. Our study shows that a characterization of physiological traits of seeds, such as germination, dormancy and desiccation tolerance, may lead to favoring the seed as a means of propagation for ornamental uses and conservation.