Direct somatic embryogenesis in dependent on the topophysical position of the explant in cactus Copiapoa tenuissima Ritt. forma monstruosa
Keywords:Cacti, somatic embryo, topophysis.
Cactus Copiapoa tenuissima Ritt. f. monstruosa is a C. tenuissima Ritt. spontaneous mutant. This form has nearly black epidermis and it has no thorns in areoles, and it is very rare and attractive for collectors. Micropropagation is an attractive method for conservation and propagation of rare species of plants. Somatic embryogenesis is most efficient from all methods of multiplication. There was investigated the induction of direct somatic embryogenesis of C. tenuissima Ritt. f. monstruosa depending on the topophysical explant position on the donor plants. The explants were cultured on the modified medium with 2 mg?dm-3 auxin 2.4-D (2.4-dichlorophenoxyacetic acid) or MS medium without growth regulators (as control). The cultures were kept in a growth room at 24 ? 2°C and exposed to 16 h photoperiod. Daylight was by maintained using Philips TLD54/36 W lamps with the photon flux density of 38.1 ?mol?m-2?s-1. The induction of somatic embryogenesis in the cacti C. tenuissima Ritt f. monstruosa was obtained only when the media were supplemented with auxin 2.4-D. However, most explants regenerated somatic embryos derived from the distal and central zone of main shoots of donor plants and from young axillary shoots (to 0.26 per one inoculated explant); yet from the proximal part of the main shoot of cacti, the number of explants which regenerated somatic embryos was low (0.02 per inoculated explant) and did not differ from the control.