Light transmission in window-leaved plants
Window-leaved plants are succulent plants which possess areas of clear epidermis on their leaves. The underlying water storage tissue is transparent to allow light penetration to the internal chlorenchyma. The most highly evolved window-leaved plants with the most transparent tissue grow completely underground in desert regions. Only the rounded leaf tips are level with the soil surface and directly exposed to incident light. Light transmission curves were measured using live windows of five species of plants from three families (Liliaceae, Piperaceae, Mesembryanthemaceae). These results suggest that subterranean window leaves may be limited to a relatively short effective maximum length because of light absorption by the tissues involved. Scanning electron micrographs (SEM) of these plants show considerable differences in surface structure which may help to modulate incident light. Comparisons with related Mesembryanthemaceae illustrate that a complex series of adaptations have been developed to allow un...