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UDP‐glucose pyrophosphorylase (EC 2.7.7.9) has been highly purified from the plant fraction of soybean (Glycine max L. Merr. cv Williams) nodules. The purified enzyme gave a single polypeptide band following sodium docecyl sulphate polyacryla‐mide gel electrophoresis, but was resolved into three bands of activity in non‐denaturing gels. The enzyme appeared to be a monomer of molecular weight between 30 and 40 kDa. UDP‐glucose pyrophosphorylase had optimum activity at pH 8.5 and displayed typical hyperbolic kinetics. The enzyme had a requirement for divalent metal ions, and was highly specific for the substrates pyrophosphate and UDP‐glucose in the pyrophosphorolysis direction, and glucose‐1‐phosphate and UTP in the direction of UDP‐glucose synthesis. The Km values were 0.19 mM and 0.07 mM for pyrophosphate and UDP‐glucose, respectively, and 0.23 mM and 0.11 mM for glucose‐1‐phosphate and UTP. The maximum velocity in the pyrophosphorolysis direction was almost double that for the reverse reaction. UDP‐glucose pyrophosphorylase did not appear to be subject to a high degree of fine control, and activity in vivo may be regulated mainly by the availability of the substrates.

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Microsporogenesis, embryogeny and endosperm development of Lomandra longifolia Labill. are described in detail. The formation of the anther wall is the basic type composed of four cell layers, namely an epidermis, an endothecium, one middle layer and a tapetum. The tapetum layer has glandular, uninucleate cells. Successive cytokinesis follows meiosis, subsequently forming a tetrahedral tetrad of microspores. The ovule in each carpel is hemitropous, crassinucellate and bitegmic, with the micropyle formed by the inner integument. The archesporial cell divides periclinally to form the primary parietal and primary sporogenous cells. The sporogenous cell functions as the megaspore mother cell, whereas the parietal cell divides to give rise to two parietal layers. The mature megagametophyte, which has enlarged synergids and antipodals, is of the Polygonum type, with the normal complement of seven cells and eight nuclei. Nucellar tissue in the mature ovule consists of enlarged dermal cells and irregular subdermal cells surrounding a central strand of markedly smaller cells. Endosperm development is of the nuclear type. Embryo development is of the Graminad type, characterised by oblique zygotic and early pro-embryonic divisions.

The micromorphology and histology of the development of male and female flowers of the dioecious Australian endemic species Lomandra longifolia Labill. was studied by means of scanning electron microscopy and light microscopy of entire and sectioned material. Although mature flowers are functionally unisexual, in the early stages of development pistillate and staminate flowers are identical and apparently bisexual. In a sequential fashion, six perianth parts are initiated within two alternating whorls, the sepals first and the petals second; six stamens are initiated in two alternating whorls of three stamens each, the first opposite the sepals and the second opposite the petals; and last, a central gynoecium is initiated. Following initiation, the two flower types diverge developmentally when the stamens become bilobed. In male flowers, cytological analysis of the slowly growing abortive pistil shows that megasporogenesis does not occur. Pistil abortion happens before meiosis whereas the stamens continue to develop until maturity and dehiscence. In female flowers, stamen arrest occurs before the onset of meiosis in microspore mother cells, after which the pistil continues its development through megasporogenesis and megagametogenesis. In all, 14 stages of floral development of both male and female flowers have been designated. Stages 1–6 of the two flower types were common to both sexes.