Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 94 (5), 733-40

The Structure of Colleters in Several Species of Simira (Rubiaceae)

Affiliations

The Structure of Colleters in Several Species of Simira (Rubiaceae)

Denise Espellet Klein et al. Ann Bot.

Abstract

Background and aims: Colleters are secretory structures consisting of a parenchymatic middle axis surrounded by a layer of palisade-like epidermal cells. Colleters occur in a large number of rubiaceous species. Their function is to protect the developing shoot apex. They are also taxonomically useful in the Rubiaceae. This study characterized the structure of the colleters of Simira glaziovii, S. pikia and S. rubra and the biochemistry of secretions in S. glaziovii.

Methods: Stipules of the shoot apices of the three species studied were collected at Barragem de Saracuruna, in Rio de Janeiro state, Brazil. The samples were fixed according to the usual methods for light and electron microscopy. Secretion stipules of S. glaziovii were washed with 0.1 m Tris-HCl plus 0.1 %Triton X-100 to extract proteins and carbohydrates.

Key results: Colleters in these species are located at the base of the stipule. Each species shows a different pattern of distribution. They form as emergentia from the stipules. Simira glaziovii was different from the other two species because it exhibited vascular traces. The epidermal cells of colleters have dense cytoplasm, nuclei, small vacuoles, endoplasmic reticulum, Golgi apparatus, mitochondria and extraplasmic spaces if they are secretory. The outer cell wall of the mature colleters differs from the outer cell wall of stipule cells and immature colleters. Both carbohydrates and proteins were found in secretions from the stipules of S. glaziovii.

Conclusions: Few ultrastructural differences were noted among the three species. These secretory structures not only protect the shoot apex, but also have taxonomic importance below the genus level.

Figures

F<sc>ig</sc>. 1.
Fig. 1.
Stipules detached from the shoot apex and observed with the aid of a stereomicroscope. (A and B) Colleters of Simira glaziovii at (A) initial stage and (B) fully developed. Note the triangular organization at the base of stipule (arrows in A). (C) Colleters of S. pikia and (D) colleters of S. rubra. Scale bars: A, C and D = 125 µm; B = 1·0 mm. Asterisks, colleters; s, secretion; st, stipule; stars, immature colleters.
F<sc>ig</sc>. 2.
Fig. 2.
Scanning electron microscopy. (A and B) An overview of the colleters of Simira glaziovii at (A) entirely developed and (B) initial stage; (C) an overview of the colleters of S. rubra; (D) cross-section of a colleter of S. glaziovii; and (E) longitudinal section of a colleter of S. pikia. Scale bars: A and B = 100 µm; C = 250 µm; D and E = 25 µm. Asterisks, colleter; stars, immature colleters; ec, epidermal cells; p, parenchyma; s, secretion; st, stipule.
F<sc>ig</sc>. 3.
Fig. 3.
Light microscopy. (A and B) Cross-sections of the colleters of Simira glaziovii at (A) initial stage and (B) fully developed; (C) cross-section of the colleters of S. pikia; and (D) longitudinal section of a colleter of S. rubra. Scale bars: A, B and D = 50 µm; C = 60 µm. Stars, immature colleters; arrow, constriction; ec, epidermal cells; p, parenchyma; s, secretion; st, stipule; vc, vascular trace.
F<sc>ig</sc>. 4.
Fig. 4.
Transmission electron microscopy. (A–C) Secretory cells of Simira glaziovii in (A) immature stage, (B) intermediate stage and (C) mature stage of development; (D and E) secretory cells and (G) Golgi apparatus of S. pikia; (F) outer cell wall and organelles of the secretory cell of S. rubra; and (H) bacteria adjacent to the outer cell wall of the colleter of S. glaziovii. Scale bars: A = 1·0 µm; B and C = 2·5 µm; D = 1·7 µm; E = 1·1 µm; F = 0·4 µm; G and H = 0·25 µm. Asterisks, extraplasmic space; er, endoplasmic reticulum; g, Golgi stacks; gv, Golgi vesicles; m, mitochondria; open stars, microorganisms; n, nucleus; curved arrows, plastid; square parenchymatic cell; v, vacuole; arrows, cuticle proper; triangle, cuticular membrane; open triangle, polysaccharide layer; open square, fibrilar structures; stars, debris.
F<sc>ig</sc>. 5.
Fig. 5.
SDS–polyacrylamide gel electrophoresis of proteins from Simira glaziovii secretion. A, Ammonium sulfate fraction; B, ammonium sulfate fraction treated with β-mercaptoethanol; M, markers (kDa).

Similar articles

See all similar articles

Cited by 5 articles

Publication types

MeSH terms

Feedback