Strengthening systems in the leaf

Strengthening systems in the leaf

Mature leaves may contain additional marginal strands of sclerenchyma, and some fibre strands or girders may be associated with the vascular bun-dles (Fig. 6.20; Aegilops crassa, Phalaris canariensis and Agave franzosinii). Collenchyma is frequently present in the raised ribs above and below the midrib bundle, and is also occasionally found in similar positions in relation to the large and intermediate vascular bundles in monocotyledons as illus-trated in Fig. 6.20(d), where ad- and abaxial hypodermal sclerenchymatous girders subtend this large bundle. Figure 6.20(e) shows an intermediate vascular bundle, in which the adaxial hypodermal sclerenchymatous gird-ers extend, and are associated with prickle hairs on the upper and lower leaf surfaces. It is important to note that the hypodermal strands or girders found in leaves of the Poaceae and Cyperaceae, for example, may become sclerified in mature leaves.