Fenestraria rhopalophylla subsp. aurantiaca leaves

The club-shaped leaves of Fenestraria rhopalophylla subsp. aurantiaca show only their flat to slightly bulging, rounded tops above the sand in a compact cluster, or sometimes short cylindrical upper sections, depending on the vagaries of the wind over the sand.

The specific name, rhopalophylla, is derived from the Greek words rhopalon meaning a club that is thicker at one end and phullon meaning leaf, referring to the leaf-shape. The biggest part of the 2 cm long leaf bodies are below ground. The visible leaf parts have a waxy covering with smooth sides and clear, transparent windows on top.

The window plant name, also reflected in the generic Latin name, Fenestraria, refers to these leaf-top windows. In most plant leaves photosynthesis is associated with water loss through the leaf stomata or tiny pores, enhanced by the heat accompanying sunlight.

Window plants of desert conditions minimise moisture loss while still photosynthesising, for which sunlight (from outside) and chlorophyll (inside the leaves) are required. The structure ensuring this in a window plant consists of small, exposed leaf areas as in the photo, plus the substructure below where the chlorophyll can be reached.

Sunlight travels through both the transparent leaf epidermis up top and the water-storing, light conducting tissue of the thick leaf body below, reaching the photosynthetic tissue embedded in the underground wall of the leaf. The photosynthetic surface below is therefore large, while the transpiring surface above is small.

This means that plant food can be manufactured underground in adequate quantities, while exposure to moisture loss remains minimal.

Simultaneously protected and enabled in one of nature’s ingenious designs, the miracle of large golden flowers is celebrated annually in desert conditions, quietly but colourfully (Grenier, 2019; Frandsen, 2017; Williamson, 2010; Smith, et al, 1998).