Now that springtime is upon us in New Zealand, many plants are starting to flower, producing pollen. Many of us have a negative association with pollen due to its role in causing allergies [PDF, 172KB]. But not all pollen causes allergies, and pollen is of course extremely important to the biology and ecology of flowering plants.
Some important research areas in palynology (the study of pollen) include analysing fossil pollen to infer past climate and vegetation (palaeoecology), studying the pollen found on a crime scene as a tool in court cases (forensic palynology), and determining how a plant reproduces and what pollinates it (pollination and reproductive biology).
In addition to being scientifically useful, I find the SEM images of forget-me-not pollen to be stunningly beautiful! Have a look at the photos yourself on Te Papa’s Collections Online, and let me know if you agree.
Just as different plants have different types of leaves, flowers, roots, and fruits that we can use to identify them, so too does pollen differ among plants. So studying pollen grains can be very useful in taxonomy and evolutionary studies of families, genera, and species of plants.
Previous studies had shown that in forget-me-nots (Myosotis, Boraginaceae) pollen was quite variable morphologically, and could be used to distinguish species from different hemispheres. Furthermore, the New Zealand species in particular could be categorised into at least 4 different pollen types, which means it might be possible to use pollen to distinguish species or groups of species from one another.
Intrigued by these preliminary studies, I decided to study the pollen of a group of New Zealand forget-me-not species (including one new species that was highlighted in my blog post about Te Papa’s exhibition, You Called Me What?!) using scanning electron microscopy (SEM).
Based on my study, now published in New Zealand Journal of Botany, pollen characteristics do appear to be taxonomically useful in New Zealand Myosotis.
The pollen grains were small (under 20 μm, which is just a bit wider than most bacteria or red blood cells, but narrower than the width of a human hair), granulate and largely spheroidal. The pollen is classed as heterocolpate because each grain has 8, 10 or 12 total openings (apertures) of two different kinds (colpori and pseudocolpi). The number of apertures, shape and presence of a polar cap were all important distinguishing features in forget-me-not pollen.
Needless to say, I learned a whole new vocabulary [PDF, 2.8MB] when working on this project!
Special thanks to Niki Murray at the Manawatu Microscropy and Imaging Centre for preparing and imaging the pollen.
Research Scientist, Botany