The growing period of the deep-rooted, winter-deciduous Capparis spinosa (caper) coincides with the dry season, in the Mediterranean Basin. Roots of wild shrubs of C. spinosa penetrated cracks of a pumice substrate and lengthened in the subterranean environment of the ancient catacombs of Milos Island (Greece); therein, they reached depths of up to 20 m and exploited water present in deep soil layers. Elevated water potential (Ψ) was measured in root segments (Ψr = −0.35 ± 0.06 MPa), a few centimetres from the root apices of C. spinosa found in the catacombs during the dry season. Also, estimates of foliar predawn water potential and gas exchange components, as well as of nocturnal floral water potential of C. spinosa grown on slopes above the subterranean monument were high and reflected the efficiency of roots in retaining acquisition of water from deep soil layers, during the dry season.

A model of floral reflectance of petals with conically-shaped epidermal cells is presented for Nerium oleander and Oxalis pes-caprae. The model was achieved by combined microscopic-scale structures and optical properties of petals; the model theory was based on concepts of physical laws, analytic geometry, vector analysis and micro-optics. The model is shown to fit experimental data of floral reflectance. Conically shaped, adaxial, epidermal cells of petals have focal regions, where incident light rays are focused on the centre of cells. Within tissues light is selectively channelled into sites containing light absorbing pigments. Particular attention was given to consequences of focusing of light within conical, epidermal cells of petals with respect to blossoming regulated by photoperiod, which acts to insure that flower opening occurs during suitable, environmental conditions.