Rates of apparent photosynthesis in leaf discs of some tropical woody plants

Rates of apparent photosynthesis were measured manometrically for Terminalia ivorensis A. Chev., Ceiba pentandra (L) Gaertn., Musanga cecropioides R. Br., Chlorophora excelsa (Welw.) Benth and Theobroma cacao L., using leaf discs of 1-2 year-old seedlings at varying levels of irradiance and 27 centigrade grade. At the highest level of irradiance, 300-400 Wm-2, maximum rates measured for single determinations were 29.4, 28.6, 22.6, 21.0 and 12.6 mgCO2dm-2h-1 respectively for the above species, approximately in the same order as previously found for their maximum net assimilation rates. The values are lower than corresponding rates measured for herbaceous plants in the same investigation: Helianthus annuus (41.8), Amaranthus edulis (32.6) and Vigna unguiculata (32.0). The data confirm the view that the lower rates of growth of woody plants when compared with herbaceous plants, are due to low photosynthetic rates in the former