Seed crop and seed weight of the dominant deciduous tree species in African miombo woodland, Brachystegia spiciformis, varied between years. Seeds possessed no dormancy and germinated completely after imbibition. First phase of seedling growth (2 weeks) is completely based on energy and nutrients allocated in the large cotyledons. The scarcity of stomata on cotyledons did not allow an important net photosynthesis of these plant parts. Low seed weight gave slow-growing seedlings. Optimum temperature for photosynthesis was at 30°C; photosynthesis at higher temperature interfered with the closing movements of the leaflets. At the time of abscission of the cotyledons (38-75 days after germination) nearly 80% of nitrogen and potassium, 65% of magnesium, and 50% of phosphorus and copper had been exported from the cotyledons to the seedling. Late abscission of the cotyledons was negatively correlated with growth performance, being a good and early selection criterion for forestry.
Journal articles from the Grassland Society of Southern Africa (GSSA) African Journal of Range and Forage Science as well as related articles and reports from throughout the southern African region.