Biology of afroalpine Dendrosenecio ( Asteraceae )

摘要: The genusDendrosenecio (“giant groundsels”), encompassing three species and 12 subspecies, is endemic to the high mountains of East Central Africa where it constitutes most conspicuous components afroalpine vegetation. Two lifeforms, arborescent prostrate rhizomatous, are regarded as results evolution from forest-living woody or herbaceous ancestors. Due uninterrupted growth period in tropics, there no anatomical morphological features which allow conventional age determination. However, stem elongation rates have been determined (3–5.5 cm per year) indicate an about 250 years for tallest Dendrosenecios may reach a height 10 m. 30 120 large leaves clustered enormous terminal rosette, justifying term “giant rosette” plants. A leaf bud, consisting many developing rosette contains, found center. During nocturnal frost adult form so-called night-bud by nyctinastic upwards bending thus protect bud freezing insulation. surrounded mantle persistent dead leaves; this ameliorates microclimate pith-cells greatly contribute water transport into leaves. Below zone putrefaction found, decay apparently provides nutrients directly growing stem. population dynamics arborescentD. keniodendron characterized simultaneous inflorescence development at irregular intervals up more than twenty years. sporadic flowering seedling survival rate less 1%, oscillations size be expected.