Abstract Detail

Reproductive Processes

Taylor, Mackenzie [1], Aeilts, Luke [2], Altrichter, Kristine  [3], Dang, Christie [4], Giffei, Bridget [5], Wilden, Ana [6].

Pollen development across the pollen lifecycle in Ruppia maritima (Alismatidae): Insight into the consequences of the ecological transition to hydrophily.

Transitions to water-pollination (hydrophily) have been repeatedly accompanied by modifications in pollen development. However, comprehensive investigations of pollen development in hydrophilous plants, particularly that which occurs after pollination, are limited. The objective of this study was to characterize pollen structure and development across the entire pollen lifecycle, from microsporogenesis to fertilization, in the hydrophilous angiosperm Ruppia maritima. Field collections and experimental pollinations were conducted, followed by analysis with combined light, scanning electron, and transmission electron microscopy. Anthers and developing pollen grains at the sporogenous, microspore mother cell, tetrad, ‘free’ microspore, and mature grain stage were documented, as was pollen germination and pollen tube development in the carpel.
Divergence in exine development between the proximal and distal walls occurs during the free-microspore stage, resulting in heteropolar pollen grains with a reduced exine on much of the distal surface. On the proximal surface, muri that comprise the reticulum consist of a solid band of sporopollenin, with no infratectal columellae. A distinct foot layer surrounds the entire microspore. Tapetal cells invade the anther locule before meiosis and this timing supports the close relationship of Ruppiaceae and Cymodoceaea. On stigmas, the majority of pollen grains germinated within 15 minutes. Pollen tubes first entered the ovule 45 minutes after pollination and by 60 minutes after pollination most ovules had been entered.
Modifications to the pollen developmental program in Ruppia give rise to traits that are hypothesized to be adaptive for water pollination. Pollen development in Ruppia will be compared to what is known from other hydrophilous species, as well as closely-related wind and animal-pollinated species and the role of pollen ontogeny in ecological transitions will be discussed.

1 - Creighton University, Department Of Biology, 2500 California Plaza, Omaha, NE, 68178, USA
2 - Creighton University, School of Medicine, 2500 California Plaza, Omaha, NE, 68178, USA
3 - North Dakota State University, School of Natural Resources, Fargo, ND, 58108, USA
4 - Creighton University, School of Dentistry, 2500 California Plaza, Omaha, NE, 68178, USA
5 - University of California, Davis, Department of Plant Sciences, One Shields Ave., Davis, CA, 95616, USA
6 - University of Minnesota, School of Public Health, 420 Delaware Street SE, Minneapolis, MN, 55455, USA

Keywords:
Alismatales
Ruppiaceae
exine
hydrophily
pollen development
pollen germination
pollen tube growth.

Presentation Type: Oral Paper
Session: 29, Reproductive Processes II
Location: 111/Mayo Civic Center
Date: Tuesday, July 24th, 2018
Time: 2:15 PM
Number: 29004
Abstract ID:252
Candidate for Awards:None