Margaret Sedgley

Arabinogalactan-proteins are localized extracellularly in the transmitting tissue of Nicotiana alata link and otto, an ornamental tobacco

Abstract The localization of a class of proteoglycans, the arabinogalactan-proteins (AGPs), within mature styles of N. alata has been examined using three probes: (1) β-glycosyl Yariv reagent, a red dye which is used as a cytochemical stain for light microscopy, (2) monoclonal antibodies to terminal α- L -arabinofuranosyl residues which bind to the terminal α- L -arabinofuranosyl residues of AGPs, (3) monoclonal antibodies to terminal β- D - galactopyranosyl residues which bind to style glycoconjugates including the AGPs. The monoclonal antibodies were used in both immunofluorescence and gold immunocytochemical studies. Staining with all probes indicates that the AGPs are present mainly in the extracellular matrix of the transmitting tissue.

Storage of avocado pollen

SummaryAvocado pollen was stored at a range of temperatures and relative humidities (RH) for up to one year and the pollen was tested for viability in vivo.Pollen stored for one month was capable of germination on the stigma and penetrating the ovule when stored at 4°C with <1,23,55 and 75% r.h. and at -196°C with 0% r.h. Most pollen samples stored at 25 and -15°C at a range of r.h. would germinate on the stigma but none would penetrate the ovule.After one year of storage, pollen at 4°C and <1 and 23% r.h. would germinate on the stigma but would not penetrate the ovule. There was no germination of pollen stored at 4°C and 55 and 75% r.h. Only pollen stored at -196°C and 0% r.h. would penetrate the ovule, but thawing and refreezing once during the year destroyed the viability.

Structure and histochemistry of the extrafloral nectary ofAcacia terminalis (Salisb.) MacBride (Leguminosae, Mimosoideae)

SummaryThe extrafloral nectary ofAcacia terminalis is of the flat type and is located on the adaxial surface of the petiole of the bipinnate leaf. The secretory area is restricted to the base of the trough and no gaps or pores were detected by staining with vital dyes. Between the vascular bundles beneath the nectary and the surface cuticle there were three cell types. The cells of the flanking zone adjacent to the vascular bundles did not appear to be producing secretion whereas the cells of the glandular and secretory zones were secreting. The cells of the glandular zone were elongated whereas those of the surface secretory zone were spherical. Both had endoplasmic reticulum and Golgi bodies with secretory vesicles which were observed in close association with the plasmalemma. Secretion accumulated in the intercellular spaces of the glandular zone cells and forced the cells of the secretory zone apart. Symplastic contact was maintained in all cell types by plasmodesmata which were often associated with endoplasmic reticulum. Secretion accumulated beneath the cuticle which was distended but remained intact on the surface of the secretion.

Foreign Pollination of the Stigma of Watermelon (Citrullus lanatus [Thunb.] Matsum and Nakai)

The effect of foreign pollen on the stigma of watermelon (Citrullus lanatus [Thunb] Matsum and Nakai) was studied by light and electron microscopy. Pollen of 14 of 15 tested species germinated on the stigma, and pollen tubes of eight species penetrated the style. Only watermelon pollen tubes reached the ovary. Pollen of all species stimulated stigma secretion, irrespective of germination capacity. Secretion was also stimulated by dead watermelon pollen, live yeast cells, and fixed red blood cells, but not by glass fragments. Prior foreign pollination did not affect germination or pollen-tube growth of subsequently applied watermelon pollen which produced fruit set. Foreign pollination did not result in fruit set, but stimulated the same sequence of papilla-cell senescence as watermelon pollen. We concluded that the processes of stigma secretion and papilla-cell death in response to pollination do not control the growth of foreign pollen on the watermelon stigma.

STRUCTURE AND SECRETION OF THE EXTRAFLORAL NECTARIES OF AUSTRALIAN ACACIAS

ABSTRACT The extrafloral nectaries of A. pycnantha and A. myrtifolia are quite different morphologically but very similar ultrastructurally. The porate nectary of A. pycnantha has a deep goblet-shaped depression in transverse section with the secretory region at the base of the depression. The non-porate nectary of A. myrtifolia is a flattened gland with the secretory region in the centre of the nectary disc. In both species there are three cell types between the network of vascular bundles at the base of the nectary and the surface. The flanking zone consisted of thin-walled cells which merge into the glandular zone of thick-walled secretory cells. Carbohydrate, protein and lipid secretion products are visible in the intercellular spaces between the glandular cells and those of the surface secretory zone, which are loosely arranged. These nectar components appear to be transported outside the cell by both eccrine and granulocrine processes. The cuticle, very thin in the secretory zone, is distended by th...

Developmental Anatomy of the Avocado Stigma Papilla Cells and Their Secretion

The development of the avocado stigma was observed by light and electron microscopy from ca. 3 wk prior to anthesis to flower opening. The stigma papilla cells grew from 50 to 250 μm long. At the earliest stages the cells had many features of the mature cells, including extensive smooth endoplasmic reticulum and dictyosomes. Plastid clusters appeared at 3 days and wall thickenings containing lipid at 2 days prior to anthesis. Some secretion containing carbohydrate and protein was present at all stages, but secretion of most of the carbohydrate and all of the lipid occurred during the 2 days prior to anthesis. The lipid bodies appeared to become surrounded by carbohydrate, as stained by the thiosemicarbazide-silver proteinate method, prior to passing through the wall thickenings by eccrine secretion. This method also stained the secretion, cell wall, dictyosomes, and plastids. Serial sectioning showed that most of the plastid clusters were arranged with the large starch-containing heads on the periphery and the long tails pointing toward the center. Many plastids were large and complex, but the clusters were composed mainly of discrete organelles. We suggest that the plastids have a role in the lipid secretion of the papilla cells, which passes through the wall, along with some carbohydrate, by eccrine secretion via specialized areas of thickened cell wall.