Figure 2.

Morphological characteristics of cactus stem and trichomes. (A) Cross-sectional image of a cactus consisting of spines, trichomes, and mucilage. (B) Fluorescent images of the cactus stem (i) unstained and (ii) stained with Nile red, a hydrophobic fluorescence probe. The fluorescent parts, such as cactus spines, trichome cluster, and surface of the stem, have hydrophobicity. (C) (i) SEM image of spines and trichome cluster. (ii) The tip part of a trichome has a conical shape with an apex angle of 17°. (iii) Magnified image of the region marked by red dotted square in (ii). Hundreds of nanogroves exist on the surface. (iv) The base part of the trichome also has (v) hundreds of nanogroves. However, its roughness is less than that of the tip part. (vi) Bottom view of the trichome cluster. All trichomes are adhered toward the center of the trichome cluster. Scale bars, 250 μm (A) and 200 μm (B).