A NOMARSKI INTERFERENCE STUDY OF MEGASPOROGENESIS AND MEGAGAMETOGENESIS IN SMELOWSKIA CALYCINA (CRUCIFERAE) |
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Authors: | Craig W Greene |
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Institution: | Gray Herbarium, Harvard University, Cambridge, MA, 02138 |
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Abstract: | Ovule development, megasporogenesis and megagametogenesis in an aneuploid population of the arctic-alpine crucifer, Smelowskia calycina, were examined to test for the possibility of apomictic seed production. Whole mounts of ovules cleared in Herr's “4½” clearing fluid were examined using Nomarski differential interference microscopy. The campylotropous ovule was bitegmic, with a micropyle formed by both integuments. The single archesporial cell of a crassinucellar nucellus functioned directly as a megasporocyte, dividing to form a linear tetrad of megaspores. The chalazal megaspore divided to form an 8-nucleate, 7-celled gametophyte of the Polygonum type, having hooked synergids with a well-developed filiform apparatus and polar nuclei that fused prior to fertilization. In the absence of any anomalous development indicative of agamospermy, seed production was assumed to be sexual. |
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