Anatomical adaptations in the leaves of selected fynbos species

Abstract

Fynbos plants experience very harsh conditions during the hot and dry summer months and their leaves are adapted to reduce the loss of water due to transpiration. The leaves of 46 selected fynbos species of 24 families were examined to determine which anatomical adaptations contribute to the reduced rate of transpiration and subsequent reduced water loss. Without exception, all species examined show leaf adaptations typical of xerophytic species. Four typical leaf types are recognized and proposed as models of leaf adaptation: 1. Myrsine type — dorsiventral or isobilateral leaves; more palisade parenchyma present than spongy parenchyma; tissues contain large amounts of phenolic substances. 2. Metalasia type — small dorsiventral leaves with involute margins and a single groove in the adaxial surface; mesophyll is usually inverted. 3. Retzia type — dorsiventral or isobilateral leaves with revolute margins and one or two grooves in the abaxial surface; spongy parenchyma is the main component of the mesophyll. 4. Spatalla type — small centric or near-centric leaves; little or no spongy parenchyma tissue.