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ULTRASTRUCTURE OF STEWARTIOTHECA (MEDULLOSACEAE) PREPOLLEN
Author(s) -
Millay M. A.,
Rothwell G. W.,
Eggert D. A.
Publication year - 1980
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1980.tb07645.x
Subject(s) - ultrastructure , biology , homogeneous , scanning electron microscope , anatomy , botany , composite material , materials science , physics , thermodynamics
Ultrastructure of prepollen from the medullosan seed fern Stewartiotheca warrenae Eggert and Rothwell has been studied with the scanning electron microscope. Nitrocellulose (“liquid” type) peel preparations of pollen organ sections were placed on millipore filters and the grain fragments were extracted by rinsing the peels with acetone. Prepollen is of the Monoletes ‐type and is elliptical in polar view, averaging 264 μm long and 183 μm wide. Individual grains possess two deep, crescent‐shaped grooves on the distal surface and a monolete suture with a median deflection proximally. The exine is constructed of a thick (1–2 μm), homogeneous nexine layer overlain by a sexine that is characterized by interconnecting spheroidal chambers. Chamber diameter decreases only slightly from the exterior of the sexine, inward, but the frequency and degree of interconnection among the chambers increases noticeably toward the interior of the wall layer. With regard to this latter feature the prepollen of Stewartiotheca appears intermediate between the organizations known for other Monoletes grains. The grains of Stewartiotheca compare most closely with those of Dolerotheca and Sullitheca .