Anatomical Adaptations of Boerhavia L. and Commicarpus Standl. (Nyctaginaceae) for Survival in Arid Environments of Namibia

Abstract

Members of the Nyctaginaceae Jussieu. are distributed throughout southern Africa. Eight species of the family occur naturally in arid parts of Namibia. These species have acquired the ability to survive and reproduce in these dry conditions. They are xerophytes, which have been described as drought evaders, avoiders, and drought-tolerant. In the Nyctaginaceae, Boerhavia deserticola, B. hereroensis, Commicarpus helenae and C. squarrosus are thought to be drought avoiders. In this study we investigated their stem, leaf and anthocarp anatomy for adaptations to arid environments. The results indicated that the four species are avoiders, with modifications of the trichomes, secretions, crystals, secondary growth, Kranz mesophyll, water storage cells, tannins, mucilage, inner and outer stomatal ledges, large-diameter xylem vessels, and the presence of sclerenchyma in their stems, leaves and anthocarps. These adaptations enable the plants to tolerate arid conditions, conserve water and maintain a high photosynthetic rate, and aid seed dispersal.K Ke ey y w wo or rd ds s: : Adaptations, arid environment, avoiders, Boerhavia, Commicarpus, Namibia, xerophytes.

One-Seeded Fruits in the Core Caryophyllales: Their Origin and Structural Diversity

“…In both families the complicated pericarp histology has evolved in the upper part of the fruit, while its structure in the lower half comprises homocellular thin-walled cells. The function of the crystalliferous layer is not clear, but it may impede the transmission of sunlight to the underlying tissue [ 125 ].…”

Radial arrangement of apical adhesive sites promotes contact self-alignment of fruits in Commicarpus plants (Nyctaginaceae)

“…1a ). The shape of the anthocarp and the arrangement of glands are species specific for Commicarpus 7 , 8 . The shape of the anthocarps varies in different species from cylindrical, fusiform, clavate to elliptic clavate.…”

Structural features of species of Asteraceae that arouse discussions about adaptation to seasonally dry environments of the Neotropics

“…Stomatal ridges and epicuticular striae and waxes are important to the successful distribution of these species in seasonally dry environments because they increase water flow to the epidermal surface and hinder water and solute diffusion through the cuticle (Struwig et al 2011;Evert 2013). The amphistomatic character of leaves of P. purpurascens differs from that described for other species occurring in seasonally dry environments and, allied with the aerenchyma in xylopodia, may reflect the main structural adaptations of this species to the seasonally dry Chaco environment, which is subjected to both stress from water deficit and excess in the dry and rainy seasons of the Pantanal, respectively.…”