Luke Aeilts
Project Description
"Pollen Development in Ruppia"
The aquatic plant Ruppia maritima is found in shallow lakes and along coastlines throughout the world. Ruppia is a member of the early-divergent monocot group Alismatales and is, therefore, a species of interest in the study of angiosperm evolution. Despite this, little is known about Ruppia pollen. The objective of this study was to conduct a comprehensive analysis of Ruppia pollen at all stages of development, including the sporogenous tissue, microspore mother cell, tetrad, free microspore, and mature stages, using light, scanning electron, and transmission electron microscopy. Pollen characters, including tetrad shape, pattern of pollen wall formation, and pollen wall ultrastructure will be discussed. Ruppia pollen grains develop in great numbers within the locule. Tetragonal and decussate tetrad arrangements, which are indicative of successive microsporogenesis, are present. In early tetrads, globular sporopollenin elements form at the plasma membrane and are the first element of the wall to develop. We hypothesize that these form the bases for reticular columns. Ruppia pollen grains exhibit a heteropolar exine that is reticulate near the center of the proximal wall and atectate at the ends and along the distal surface. All regions of the wall exhibit a thin, contiguous foot layer, a lamellate endexine, and a fibrous intine layer. In addition, a layer of tapetal exudate surrounds the exine. An amoeboid tapetum permeates throughout the locular space. Ruppia exhibits a rare epihydrophilous pollination method, in which pollen grains float in “pollen rafts” on the water surface in order to pollinate flowers. Several observed morphological adaptations have evolved in Ruppia to heighten the efficacy of this pollination strategy. These include a reduced, reticulate exine, a thick layer of tapetal exudate, and an oblate, boomerang-like pollen shape that allows for grain cohesion.
The aquatic plant Ruppia maritima is found in shallow lakes and along coastlines throughout the world. Ruppia is a member of the early-divergent monocot group Alismatales and is, therefore, a species of interest in the study of angiosperm evolution. Despite this, little is known about Ruppia pollen. The objective of this study was to conduct a comprehensive analysis of Ruppia pollen at all stages of development, including the sporogenous tissue, microspore mother cell, tetrad, free microspore, and mature stages, using light, scanning electron, and transmission electron microscopy. Pollen characters, including tetrad shape, pattern of pollen wall formation, and pollen wall ultrastructure will be discussed. Ruppia pollen grains develop in great numbers within the locule. Tetragonal and decussate tetrad arrangements, which are indicative of successive microsporogenesis, are present. In early tetrads, globular sporopollenin elements form at the plasma membrane and are the first element of the wall to develop. We hypothesize that these form the bases for reticular columns. Ruppia pollen grains exhibit a heteropolar exine that is reticulate near the center of the proximal wall and atectate at the ends and along the distal surface. All regions of the wall exhibit a thin, contiguous foot layer, a lamellate endexine, and a fibrous intine layer. In addition, a layer of tapetal exudate surrounds the exine. An amoeboid tapetum permeates throughout the locular space. Ruppia exhibits a rare epihydrophilous pollination method, in which pollen grains float in “pollen rafts” on the water surface in order to pollinate flowers. Several observed morphological adaptations have evolved in Ruppia to heighten the efficacy of this pollination strategy. These include a reduced, reticulate exine, a thick layer of tapetal exudate, and an oblate, boomerang-like pollen shape that allows for grain cohesion.
Presentations
2013
Creighton University Ferlic Scholar Symposium
2014
Botany 2014 (abstract)
Nebraska Academy of Science
Creighton Biology Department Research Colloquium
Creighton University Ferlic Scholar Symposium
2014
Botany 2014 (abstract)
Nebraska Academy of Science
Creighton Biology Department Research Colloquium
Publications
Taylor M.L., *K.A. Altrichter, *L.B. Aeilts. 2018. Pollen ontogeny in Ruppia (Alismatidae). International Journal of Plant Sciences. 179: 217 – 230.