Developmental and Structural Section
Healy, Rosaria , Horner, Harry T. , Palmer, Reid G. .
Nectary development in perennial Glycine tomentella and annual cultivars of G. max: a comparative study.
Glycine tomentella, a wild perennial soybean that is suspected to outcross readily, and G. max annual cultivars that typically have less than 1% outcrossing, were investigated for characters that differ between the species. In particular, the nectaries of these species were examined and compared with each other at the following stages: 2 days before anthesis; 1 day before anthesis; anthesis before the petals open; anthesis after the petals open; 2 days after anthesis; and 3 days after anthesis. The perennial soybean flowered in racemes, with up to 4 flowers opening apically on a raceme on a given day. Flowers remained open for up to 3 days. The annual soybeans flowered at the node of a branch, with up to 2 flowers open at a node on a given day. Flowers remained open for up to 2 days before withering. Nectary development in the perennial was similar to that of the annuals except for the final stage. In both annual and perennial species, starch is present in all cells of the nectary, but is particularly concentrated in the cells to the outside of the phloem fingers. The starch is noticeably less just prior to flower opening, and almost gone after flower opening. In the annuals, the special parenchyma and epidermal cells, excluding guard cells, lose their cellular contents, and the nectary collapses. The processes of starch degradation and nectary collapse occur within the same 24-hour period. In the perennial, a zone of special parenchyma cells surrounding the phloem parenchyma becomes completely vacuolated, and collapses. However, the epidermal and special parenchyma cells, in a zone 3-10 cells deep, remain cytoplasmic even after the flower has withered, so that the nectary persists. Implications of these observed differences as they may pertain to outcrossing will be discussed.
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1 - Iowa State University, Department Genetics, Development & Cell Biology, Bessey Microscopy Facility, 3A Bessey Hall, Ames, Iowa, 50011-1020, USA
2 - Iowa State University, USDA ARS CICGR and Agronomy, Ames, Iowa, 50011, USA
floral nectary, Glycine, starch degradation.
Presentation Type: Oral Paper
Date: Monday, August 15th, 2005
Time: 2:15 PM