Developmental Anatomy of Adventitious Shoot Formation on Snapdragon (Antirrhinum majus L.) Hypocotyls In Vitro

Abstract

Developmental anatomy of adventitious shoot formation in vitro from snapdragon (Antirrhinum majus L.) hypocotyls was investigated using two inbred lines, the most (R) and least (NR) regenerative lines selected from screening (Schroeder and Stimart, 1999). Time course analysis indicated cell division in the most regenerative line occurred first in one or a small number of epidermal cells with periclinal and anticlinal divisions within 2 days of placing hypocotyls on induction medium. Subsequently, cortical then vascular cells were recruited beneath the dividing epidermal cells. Once shoots formed, their vascular system was continuous with the original hypocotyl explant. The least regenerative line had no cell division directed towards organogenesis through 6 days. Shoot formation on snapdragon hypocotyls was adventitious in origin, by direct organogenesis and genotype dependent.