Dormancy-breaking and germination requirements for seeds of the threatened Austral papaya (Carica chilensis)

Abstract

Seed dormancy is one of the most important adaptive mechanisms in plants, which optimizes germination, seedling emergence, and establishment so that these processes occur when environmental conditions are favorable for plant survival and growth. Endemic to rocky environments of the southern Atacama Desert, the Austral papaya (Carica chilensis) is the papaya species with the southernmost distribution of the Caricaceae and the species growing in the most extreme environmental conditions. This threatened plant has minimal natural regeneration, attributed to low germination rates, but no information regarding seed dormancy release exists. Here we investigated the dormancy-breaking requirements and germination of C. chilensis by assessing the combined effects of desiccation with nine pre-sowing treatments. We hypothesized that, as in other members of the family, C. chilensis seeds would possess physiological dormancy. Our results confirmed this hypothesis and revealed that ultra-drying (< 3% moisture content) and treating seeds with sulfuric acid, gibberellic acid, or potassium nitrate are the most effective methods for germinating C. chilensis. These treatments are thus recommended to propagate this threatened papaya species.