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GrainGenes Reference Report: ASA-38-432

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Reference	ASA-38-432
Title	The course of the pollen tube in cultivated barley
Journal	Agronomy Journal
Year	1946
Volume	38
Pages	432-440
Author	Pope M
Abstract	The style of the barley pistil is composed of a parenchymatous ground tissue, the cells of which are elongated, and is traversed by a lateral procambial strand extending into it from the ovary wall and an S-shaped band of conducting tissue arising at the cone-shaped projection of the outer integument The stigma hairs are apparently of epidermal origin The cytoplasm of the pollen grain is usually richly laden with small starch grains which, unless changed by enzymatic action during the growth of the tube, serve to identify and locate the tube traces when the sections are treated with weak iodine solution The direction of early growth of pollen tubes seem to be determined mechanically by the initial direction of growth and the path of least resistance No evidence of digestion of cells for nutrition or to facilitate passage of the tube was seen The course of the pollen tube is as follows: Germination of the pollen grain occurs on the stigma hair and the tube enters the central lumen through the angle between the papilla and the base of the cell just above The tube, pointed downward, traverses the hair down into the style Enlargements of the tube may occur while it pushes its way between the cells of the style and those of the ovary wall. The tube resumes its normal diameter as soon as a path through an obstruction has been made. As it enters the ovary, the pollen tube passes along the S-shaped band of conducting tissue to the cone-shaped projection of the outer integument on the upper end of the ovule, thence between the inner epidermis of the ovary wall and theo uter integument, over the abchalazal surface of the ovule, through the micropyle. It. then pierces the wall of the nucellus and discharges the male nuclei into the embryo sac.
Keyword	germination gynoecium hordeum vulgare pollen-tubes

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