Variation in baobab seedling morphology and its implications for selecting superior planting material

Abstract

With the aim of helping to select superior planting material for drought characteristics, baobab seedlings from two countries, one in western and one in south-eastern Africa, were grown in a greenhouse and their growth and morphology were studied. Seedlings were grown for 18 weeks and several morphological characteristics (length, diameter and dry weights of different plant parts, number of leaves, stomatal density, among others) were recorded at different harvesting times. Biomass allocation changed with time: seedlings invested more in fine roots and leaves in the beginning of their growth while later they invested more in the development of the taproot. In general, at any harvest time, seedlings from Malawi were larger; but seedlings from Mali had higher relative growth rates and a faster ontogeny. Seedlings from Mali had shorter hypocotyls, their stems were thicker, they had fewer leaves, lower leaf area ratios and, in general, they had a higher stomatal density than those from Malawi. Significant differences between provenances within one country could also be observed. In general, seedlings from drier provenances were smaller overall, they had fewer leaves, higher taproot water content and stomatal density, characteristics often related to drought adaptation. Seedlings from drier provenances also invested more in their taproot, a key organ for baobab seedling survival. Although our seedlings were only grown under optimal conditions in a greenhouse, results from this study indicate that there is a great variation in baobab seedling growth, biomass allocation to plant parts and morphology, which gives opportunities to select high quality planting material.