Figure 1.

Anatomical structures of barley awns. (A), The awn is a characteristic floret organ and an extension of the lemma of spikelets in barley. Shown is a twisted awn of the barley ari-a mutant grown in the green house of the University of Idaho, photo taken by B.H. (B,C), A transverse section of a typical barley awn. The chlorenchyma cells (ch) are green under transmission light microscopy due to the presence of chlorophylls (B) but are red under a fluorescent microscope because of the autofluorescence of chlorophylls (C). (D,E), Transverse and longitudinal awn sections of barley cultivar Bowman under a light microscope after staining with Safranin O, a red dye for nuclei and cell walls. On a longitudinal awn section, the chlorenchyma cells are organized as two long strands that are placed among the three vascular bundles (vb). The chlorenchyma cells are active in photosynthesis and provide a major contribution of carbon sources for grain filling. p, parenchyma cells; sc, sclerenchyma cells. Bars, 100 μm. Images of (B,C) are taken from [11] and (D,E) from [12], with permissions from publishers.