ABSTRACT
Plant geography is determined by the response of plant species to different energy regimes. The climate of the earth occurs in distinct blocks which can also be distinguished according to their vegetation. In the warm and wet tropics plants dissipate heat by evaporating water. The leaves in a tropical rain forest are flat, numerous, and stacked layer on layer to diffuse incident light. The presence and abundance of individual species will depend on ambient conditions which will vary along environmental gradients. Plant meristems produce new shoots and are particularly vulnerable to damage by frost. Grassland regions occupy a broad band between forests and deserts. Unlike most trees, which require higher levels of rainfall, the characteristics of grasses enable them to survive periodic drought and also adapt them to the stresses of fire and grazing. Acacia is characteristic of the African savannah, providing shade, food for browsing animals and supporting many invertebrate species.
