Regenerative studies on the detached leaves of Echeveria elegans. Patterns of regeneration of leaves in sterile culture

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Entire detached leaves (L30 and older) and leaf-halves of Echeveria elegans Bgr. were cultured aseptically on an agar medium to study their regenerative capacity. The entire leaves with their bases intact produced shoots and roots regardless of whether they were placed erect, inverted, or flat on the medium. Similar leaves with their bases severed and placed erect produced roots from their cut ends. The proximal leaf-halves showed a regeneration pattern similar to the entire leaves depending on, of course, whether the leaf bases were cut or not. The regeneration in the distal halves was identical to the proximal halves whose bases had been removed. In the inverted position, a few distal halves and proximal halves with their bases removed produced shoots and roots. In all leaf types, inverted, erect, or flat, the regeneration occurred at the proximal end and in some exceptional cases, roots were formed at the distal cut end too. In general, the regeneration potential appeared to be much greater in the proximal parts than in the distal parts of detached leaves and the anatomy in the former was more favorable for regeneration than in the latter. Cutting the leaf base altered the regeneration pattern in the detached leaf but it did not have any effect on the capacity for regeneration to produce differentiated organs. The leaf fragments showed strict polarity in shoot formation which occurred only in the proximal region. The roots, on the other hand, appeared at proximal and distal ends.