Adventitious buds ofdryopteris sparsa complex (dryopteridaceae): Developmental anatomy and systematic implication

Adventitious buds of theDryopteris sparsa complex were examined anatomically and taxonomically. While no buds are found inD. hayatae andD. sparsa, they occur inD. sabaei, D. yakusilvicola, and in putative hybrids of which one parent seems to beD. sabaei. The buds function as a means of vegetative reproduction in the species and hybrids. The buds arise as a pair on stipes of abortive leaves without lamina. InD. sabaei the youngest bud primordium observed consists of a small group of surface and subsurface meristematic cells surrounded by differentiated tissue cells, and the meristematic cells appear to be quiescent. As the bud primordia develop, the inner and then outer parenchymatous cells below the meristematic cells divide each into several small cells, among which the procambial strands are later differentiated to connect the bud primordium to the vascular strand of the leaf. The meristematic cells also undergo cell divisions, and the bud primordium becomes larger. A shoot organization of the bud primordium is later established. The bud-bearing, uniquely abortive leaves and delayed development of the buds support the taxonomic relationship of agamosporousD. yakusilvicola having been derived from hybridization betweenD. sabaei andD. sparsa.