Estimation of Leaf and Stem Growth of Unbranched Senecio keniodendron Trees

Abstract

Summary An attempt was made to estimate leaf growth rates of the afroalpine giant rosette plant Senecio keniodendron Fries et Fries growing at an altitude of about 4,100 m on the northwestern slope of Mt. Kenya (Kenya, East Afriea). After establishing the orthostiehes the shapes of the younger leaves were marked on the older ones at various times, namely on 28th February (dry season), 25th March (transition between dry and wet season) and 8th April (rainy season). Based on a proportionate growth of the petiole and the lamina — at least during the observation period — the true growth rates could be calculated from the intervals between the marks. Leaf growth curves showed constant growth rates from the unfolding stage until the leaf reaches its final length. From 5 specimens the numbers of leaves reaching the adult stage during the observation period as well as the dry weight were determined. An annual leaf formation of about 50 and an annual leaf biomass production of 166 g per m 2 of green leaf area were estimated. This is about half of the productivity of a 50—120 years old beech tree growing in middle Europe. From the annual leaf production and the number of marcescent and dead leaves forming the insulating mantle around the stem an annual length growth rate of 3 cm was estimated for the latter.