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Abstract Detail

Development and Structure

Rice, Ryan-Scott [1], Falconer, Denver [1], Vera Velez, Roy [1], Belliveau, Nicholas [1], Cota-Sanchez, Hugo [1].

An examination of the macro- and micro-morphology and function of staminodes in the Plains Prickly Pear Opuntia polyacantha (Cactaceae).

Staminodes exhibit a wide range of forms and occur in about one-third of angiosperm families. Traditional definitions classify them as infertile stamens, but in the heart of the Canadian Prairies, this is not the case in the Plains Prickly Pear, Opuntia polyacantha. The northernmost range of the species reaches southern Saskatchewan, Canada, where it's found in sandy hills of the mixed moist grasslands. The Saskatchewan population of O. polyacantha exhibits two types of flowers. One kind displays the distinctive graded perianth whorls of the Cactaceae (regular flower), but a second variant (staminodial flower) bears staminodes where a filament and/or anther is fused with another floral part, e.g., tepal or another stamen, often with distinctive elaborations seemingly derived from androecial and/or perianth parts. The goals of this study were to 1) characterize the macro- and micromorphology of staminodes, 2) compare pollen attributes (size, shape, and viability) in regular stamens and staminodes, and 3) discuss the putative function of staminodes. We hypothesized that staminodes contribute to an increase in flower size and play a role in pollination rather than being dysfunctional. To test this idea, optical microscopy and SEM imaging were used to examine the characteristics and ultrastructure of staminodes and pollen morphology and viability from regular anthers and staminodes. Comparative data between regular and staminodial flowers showed that flower size and overall perianth structure is influenced by the addition of staminodes leading to increases in floral width. Microscopic observations revealed a wide assortment in staminode size and shape, including spatulate, flabellate, bi- and trifurcate, and conjoined with tepals. These organs derive from fertile stamens along the androecial margins via a series of transformations involving gradual widening and amalgamation with stamens and/or tepals. Unlike the typical dysfunctional angiosperm staminodes, pollen viability counts showed that O. polyacantha staminodes produce fertile pollen similar in shape and size to regular stamens. A high proportion of viable pollen grains in staminodes contradicts the conventional idea that these appendages are sterile. Hence, we propose broadening the meaning of the term staminode as a potential fertile appendage. The presence of staminodes bolsters an increase in floral size and diameter compared to non-staminodial flowers. Thus, larger flower span serving as landing platforms combined with added viable pollen from staminodes promote visual attraction and reproductive assurance. The diversity in shape, size, and pollen viability in staminodes of this species possibly results from different levels of development and natural selection.

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1 - University Of Saskatchewan, Department Of Biology, 112 Science Place, Saskatoon, SK, S7N 5E2, Canada

floral traits

Presentation Type: Poster
Session: P1, Development and Structure Posters
Location: Virtual/Virtual
Date: Monday, July 19th, 2021
Time: 5:00 PM(EDT)
Number: P1DS006
Abstract ID:430
Candidate for Awards:None


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