By using holographic microscopy researchers expand plant classification criteria
An applied optics procedure carried out by the UNal Department of Physics contributes to extend plant classification criteria using pollen.Bogotá D. C., 09 de marzo de 2015 — Agencia de Noticias UN-
With a pollen grain researchers can measure the refractive index of a taxonomic family. Photo: UNal Archives
A grain sample is sustained by an optic fiber and rotated to gather key refractive indexes. Photos: Catalina Torres/Unimedios.
“The purpose of the project was to develop a tool to characterize pollen grains, which offer another property to classify these families,” said Professor Freddy Monroy, who along with researchers Édgar Mauricio Torres and Miguel Ángel Orejuela used digital holographic microscopy; which consists of obtaining holograms which have high and low contrast attaining information of amplitude as well as the wave phase in an optical assembly.
This project helps palynologists to determine data such as a refractive index with the purpose of extending the compendium of information gathered on taxonomic families.
Palynology is a branch of botany which studies pollen and spores. It is based on their external morphology, mainly on their size to help classify them as families, genera and species.
An important aspect of their work is calculating the refractive index which measures the degree of light that passes through an object, in this particular case a grain of pollen. Another aspect researched is a topographic rebuilding of the sample, including surface and size.
Taxonomic families have a refractive index, although the optical procedure with digital holographic microscopy shows its variation is not very large.
Indices are classified in ranges, For instance the range of water is 1.33; vacuum has an index of 1; and the strongest is diamond which reaches 2.42. The pollen grains studied are between 1.33 and 1.56, approximately. This information extends family classification by using palynology.
To study pollen researchers used a Mach–Zehnder interferometer and sustaining the grain on an optic fiber located on an axis which rotates 1.8 degrees, coupled with a computer step-controlled motor. In this manner they take tomographies with a low density laser beam,” said Science-Physics master’s candidate Édgar Torres.
In the process they hope to obtain a phase in order to become cognizant of the refractive index in each step the sample is rotated which has an outer layer known as exine, which has a different index from pollen which is also taken into consideration.
Up to now UNal Physics undergraduate Miguel Ángel Orjuela says they have worked with pollen from four species of the Poacea family.(Por: Fin/DSGM/SYC