Histological changes during the adventitious shoot formation in seedling explants of pepper (Capsicum annuum L.) cultured in vitro

Abstract

Adventitious shoots differentiated directly from explant tissue without intermediate callus on all types of examined explants (shoot tip, cotyledonary node, cotyledon and hypocotyl) of Capsicum annuum L. cv. Bryza. First cell divisions took place as early as after 3 days of explant culture within epidermal and subepidermal layers of explants, and in the case of cotyledon also within mesophyll cells located near epidermis. Mitotic activity in these layers led to the formation of meristemoids (meristematic centres). In all types of studied explants, meristematic centres appeared approximately at the same time (after about 7 days of culture). In the second week bud primordia began to differentiate from meristematic centres. Subsequently some of shoot primordia developed into leaves and leaf-like structures (mainly on cotyledon explants), and also into adventitious buds with well developed apical meristem and leaf primordia.