The effect of gut passage by waterbirds on the seed coat and pericarp of diaspores lacking “external flesh”: Evidence for widespread adaptation to endozoochory in angiosperms
Fig 3
Scanning electron microscopy of seed coat or pericarp in control and passed diaspores.
A–H. Allium angulosum. A–D. Control seeds. A. General morphology. B. Surface of reticulate exotesta; arrows indicate the “zipper-like” epicuticular wax deposits between polygonal exotesta cells. C. Cross-section showing the seed coat and endosperm; note the thick cell walls of endosperm. D. Detail of seed coat showing the layers of exotesta and wax stacks. E–H. Passed seeds. E. Seed coat was entirely removed from portions of the seeds. F. In areas where seed coat persisted, wax stacks between exotesta cells were eroded (arrows). G. Cross-section through area of seed where seed coat was entirely removed and endosperm was left at the exterior of seed. H. Surface of endosperm with remnants of tegmen cell walls. I–M. Bolboschoenus planiculmis. I–M. Control achenes. I. General morphology. J. Surface of exocarp. K. Anatomy of pericarp; note the radially elongated cells of the exocarp, which likely also functions as an aerenchyma. L–M. Passed achenes. L. Morphology; arrow indicates damage to pericarp. M. Structure of pericarp in damaged area; note the remnants of exocarp cells. N–R. Cyperus flavescens. N–P. Control achenes. N. General morphology. O. Surface of exocarp. P. Cross-section through pericarp. Q. Passed achene. R. Cross-section through pericarp of passed achene (arrow indicates area with exocarp damage). S–V. Echinochloa crus-galli. S–T Control spikelet. S. Cross-section showing spikelet layers and lemma/palea surrounding the caryopsis. T. Structure of sterile lemma. U–V. Passed spikelet. U. Cross-section through passed spikelet; note that although the upper glume and sterile lemma were removed, the caryopsis remained intact within the fertile lemma and palea. V. Cross-section through fertile lemma and caryopsis of passed spikelet. Em = embryo; En = endosperm; End = endocarp; Ep = epidermis; Exc = exocarp; Ex = exotesta; Hil = hilum area; L1 = sterile (awned) lemma; L2 = fertile lemma; Mh = macrohair; Mz = mesocarp; Ms = mesophyll; Pal = palea; P = pericarp; Ug = upper glume; V = vascular bundle; W = epicuticular wax. Scale bars = 30 μm except A, E, N, Q, S, U = 0.5 mm; I, L = 1 mm.