Summary
In the young ovule of Welwitschia mirabilis the nucellar apex is dome shaped and starch begins to accumulate near the female gametophyte. With the degeneration of the cells of the nucellar apex, a pollen chamber is formed, which contains the micropylar fluid. Starch storage increases considerably in the upper part of the nucellus. Pollen drop emission is not a rhythmic process, and pollination does not produce the rapid withdrawal of droplets. The micropylar drop consists almost entirely of sugars, uronic acids and a very small amount of free amino acids and enzymes. The mechanism of micropylar drop secretion and its probable role in the process of pollination is discussed.
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Carafa, A.M., Carratu', G. & Pizzolongo, P. Anatomical observations on the nucellar apex of Wellwitschia mirabilis and the chemical composition of the micropylar drop. Sexual Plant Reprod 5, 275–279 (1992). https://doi.org/10.1007/BF00197378
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DOI: https://doi.org/10.1007/BF00197378