Submitted to: Botanical Society of America Abstracts
Publication Type: Abstract only
Publication Acceptance Date: 8/7/2003
Publication Date: 8/7/2003
Citation: HORNER, H.T., HEALY, R., CERVANTES-MARTINEZ, T., PALMER, R.G. THE SOYBEAN FLORAL NECTARY: AN INTERESTING SECRETORY GLAND WITH UNIQUE FEATURES. BOTANICAL SOCIETY OF AMERICA ABSTRACTS. 2003. p. 24. Abstract No. 91. Interpretive Summary:
Technical Abstract: The soybean floral nectary is a small, circular mound around the base of the central gynoecium. It forms just prior to flower opening and degenerates in about 24 hours, just after the flower opens. The epidermis of the nectary contains many prominent guard cells with open pores, whereas the interior of the nectary consists of special parenchyma cells and fingers of phloem, the latter made up of sieve elements and companion cells. Once formed, each special parenchyma cell vacuole enlarges and fills with unidentified substances interspersed with ribosome-like particles. The cytoplasm is enriched with ribosomes, ER, Golgi bodies, mitochondria, and undifferentiated plastids with little or no starch but containing phytoferritin. Three unusual cytoplasmic structures appear prior to break down of these cells: bundles of tubules tightly associated with the vacuole membrane; cytoplasmic bridges extending into the vacuole; and straight tubes free in the cytoplasm and sometimes traversing plasmodesmata. The tubes contain ribosome-like particles. The special parenchyma cell cytoplasm and vacuole contents eventually mix, and each cell collapses, which in turn leads to nectary collapse. Small bead-like bodies of unknown composition occur in guard cell pores and on the nectary surface at this time. This holocrine-type of secretion suggests programmed cell death, not reported in any other legume nectary. In addition, the surface of the gynoecium displays three types of trichomes, one being glandular. The latter appears active during nectary secretion and may contribute substances, in addition to the sugars and other substances in the nectar secreted by the nectary.