Abstract
Colleters are secretory structure present on many families including
Rubiaceae. Particular characteristics have been described about
colleters secretory cells, however senescence process are still under
debate. Tocoyena bullata (Vell.) Mart. (Rubiaceae) shoot apex were
collected at Jardim Botanico do Rio de Janeiro, RJ/Brazil. Stipules were
separated and fragments were fixed in 2.5% glutaraldehyde and 4.0%
formaldehyde in 0.05m sodium cacodylate buffer, pH 7.2, post fixed in
1.0% osmium tetroxide in the same buffer, dehydrated in acetone,
critical-point-drying, sputtered coated and observed. For light
microscopy fragments were fixed and dehydrated, infiltrated with
historesin and stained with 1% toluidine blue. For transmission
electron microscopy, the samples were infiltrated with Epoxi resin.
Colleters are present on stipule adaxial surface. On the beginning of
development, these structures are recognized as small projections. Later
on, colleters differentiated and secrete by cuticle rupture. The
colleters senescence occurs in a concomitant and indissoluble way of
programmed cell death. Ultrastructural analyses during the process
strongly suggest the senescence is based on a non-autolitic programmed
cell death. T. bullata colleters, present at stipule abaxial surface are
cylindrical secretory structures. Colleters secretory cells originated
as stipule projections; differentiate; secrete and senesce by programmed
cell death. The secretion and the cell dead occurs in a concomitantly
and indissoluble way.
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