Plants, unlike mammals, continuously undergo a process of organogenesis, or the creation of different organs. Whereas mammals are born with a preformed set of organs, plants must constantly grow and develop in order to adapt to their environment. The development of the aboveground organs of the plant depends on the cells in the shoot apical meristem (SAM), the budding area of the plant where new plant tissue growth begins.

Within this hotbed of growth and change are SAM stem cells, the cells that will eventually develop to form the diverse range of tissues that create the plant. Plant scientists want to figure out how the characteristics of SAM stem cells influence the future fate of the plant. Samuel Leiboff, a fifth-year graduate student in Michael J. Scanlon’s Lab, Integrated Plant Science, aims to answer some of the fundamental questions.

As an undergraduate at the University of California, Berkeley, Leiboff worked with Arabidopsis, a well-known plant model organism. He realized, however, that he was more interested in studying plants that are more “impactful” with real world agricultural applications. While searching for graduate school, Leiboff explains that he was drawn to Cornell because of the breadth of plant science knowledge found here, stating, “There are people [at Cornell] who are experts on every plant science subject.”

At Cornell, Leiboff works primarily with different strains of naturally occurring maize. He explains that maize is a good grain to work with because it’s been extensively studied, and its genome is well mapped. His project involves approximately 400 varieties of corn from places as far as Tanzania and Thailand.

Improving the Techniques for Seeing Plant Stem Cells

Leiboff has been working to improve the techniques that let plant scientists see these microscopic plant stem cells. Instead of using traditional methods, which call for the labor-intensive process of creating and preparing microscope slides, Leiboff uses a quicker and more efficient process that employs an oil extracted from wintergreen plants to “clear” the tissue of the plant, exposing the stem cells buried underneath. By using this technique, researchers can look directly at the cells of interest.

Leiboff has also been working with a method that involves setting up specific workstations where researchers use x-rays to create three-dimensional models of a plant’s tissues. This technique allows researchers to rotate images and visualize unusual perspectives. Both methods allow plant scientists to quickly and efficiently visualize large amounts of tissue.

SAM stem cells and the Fate of the Plant

Using his improved techniques, Leiboff takes images of stem cells and analyzes them for further information. He pays special attention to the size of the stem cells and uses parabolic models to determine the shape of the meristem. By using mathematics and some computational methods, Leiboff is able to determine characteristics about the SAM that would not be possible with only a 2D view.

“The more we understand about the way plants can change, the more we’ll understand about what we can do in different situations and environments.”

The goal of Leiboff’s project is to study the relationships between the morphological differences present in the stem cells and the overall development of the plant. So far, he has found correlations between stem cell morphology and flowering time and between stem width and the number of leaves that the plant develops. Bit by bit, Leiboff is figuring out more about what factors influence these tiny cells to form the complex shapes and structures of the plant.

In addition to his work with imaging, Leiboff wants to determine the evolutionary history of shoot apical meristems from a variety of plant lineages. He is examining the shape of SAMs from plants of the same species and plants from different evolutionary lines. Leiboff found that certain shoot meristem shapes belong to certain evolutionary lines.

An Essential Biology Question

While Leiboff sees his research as primarily addressing an “essential biology question” about how plants develop, he also emphasizes the broader impact of his work. Although few farmers may be interested in using stem cells to predict the time of corn flowering, all of this information contributes to our understanding of how plants develop and form. As Leiboff states, “Our ability to use plants depends on the shapes and sizes they can take…the more we understand about the way plants can change, the more we’ll understand about what we can do in different situations and environments.” In the future, Leiboff’s work may contribute to how we choose to grow plants for adapting to the environment and society’s changing needs.

So far, Leiboff says that he’s greatly enjoyed his graduate experience at Cornell. While living in Ithaca, he has developed an interest in rock climbing and frequently travels to climb new places with friends.