Direct somatic embryogenesis on Coffea arabica L. explants previously subjected to water restriction

Somatic embryogenesis can occur either directly or indirectly. However, Coffea arabica genotypes respond inefficiently to direct somatic embryogenesis. In this way, explants of this species form small embryogenic structures (pre-embryogenic masses) and a few somatic embryos. Studies have shown that the intensity of the osmotic potential can either favor or hinder the somatic embryogenesis response in different species. Plant tissue subjected to water restriction presents a reduction in osmotic potential. Therefore, this study aimed to evaluate the direct somatic embryogenesis response of leaf explants from four genotypes of C. arabica, which were previously subjected to 0, 1, 2, 3, 4 and 8 days of water restriction. At time 0, the explants had an average humidity of 70 %, which decreased to approximately 40 % after 8 days of water restriction. Somatic embryo formation occurred in explants subjected to up to 3 days of water restriction and there was no response in those with 4 and 8 days without hydration. Explants with low intensity osmotic potential of up to -0.8 MPa formed somatic embryos, whereas this response was reduced or inhibited in those with a more negative osmotic potential. However, explants with an osmotic potential equal to or less than -1.6 MPa formed larger embryogenic structures, which is desirable as they also give rise to somatic embryos. Thus, the direct somatic embryogenesis response of C. arabica is influenced by the intensity of the osmotic potential in the explant tissue.