Plants are multicellular organisms that grow by cell division and cellular growth. These cellular processes occur at micron-scale, and they are subject to the mechanical constraints and physical laws. We study how internal and external forces act at macroscopic and microscopic levels to influence the development of a plant from embryo to adult, and to regulate the reproductive process. To do so we combine molecular biology, cell biology and high end imaging with micro-manipulation and mechanical modeling.
Below you find an overview of the general research themes and the experimental tools used in the lab. Details about recent projects can be found here.
Modeling Cell Mechanics
Plant Cell Morphogenesis
The delivery of the sperm cells in the flowering plants occurs through a tubular protrusion formed by the pollen grain - the pollen tube. It is an extremely rapidly growing cell that invades the flower pistil and fertilizes a receptive ovule resulting in embryo and seed formation. We study how the pollen tube finds its path through the complex maze of flower tissues and how it copes with obstalces in its way.
Plant cells and tissues are mechanical structures whose behavior is largely dominated by the cell wall and the internal turgor pressure. We use mathematical and computational modeling to simulate how plant cells grow, how they behave under an internal or external mechanical load, or in the context of a multicellular tissue. The modeling approaches require an understanding of the mechanical behavior of the cells.
Each tissue in a living organism has a characteristic functionality conferred by the metabolic and structural properties of its cells. Plant cells display a kaleidoscope of different shapes that are formed from geometrically very simple stem cells. We study how cellular shapes are generated and how the shape influences the functionality of each cell and tissue.
Plant Cell Wall
One of the fundamental structures distinguishing plant cells from animal cells is the cell wall, a polysaccharide-rich envelope that gives plant cells shape and rigidity. How this structure is assembled and how its mechanical properties determine the cell's behavior is a focal point of our research.
Determining the mechanical properties and behavior of single cells requires mechanical testing at the micron-scale. Using micro-manipulation through micro-indentation or micro-fluidics technology we probe the behavior of individual cells with the intent to quantify their properties.
The pollen grain is the carrier of the sperm cells in the flowering plants. To deliver its cargo, it produces a long protuberance that is able to respond to guidance cues and invade the flower tissues. To sustain its rapid growth, the main metabolic activity of the pollen tube is cell wall assembly. The pollen thus provides an excellent model system to investigate this process.
Live Cell Imaging
Cellular ultrastructure can only be studied with high resolution imaging methods. We use scanning and transmission electron microscopy to investigate the ultrastructure of the plant cell wall, and the cellular organelles to understand how the cell orchestrates the processes involved in cellular growth and morphogenesis.
Cellular functions such as cell division and growth involve shuttling components between different cellular compartments and between the inside and outside of the cell. This motion is choreographed by the cytoskeleton, a dynamic array of structural and motor proteins that is able to move cargo within the cytoplasmic space.
Observing cellular processes in motion requires live cell imaging techniques. We fluorescently label cellular structures to monitor their dynamics and to study how cellular behavior changes when the cell responds to a trigger or performs functions specific to its type.
The images shown on this and the other pages of this web site were taken by Geitmann Lab members Firas Bou Daher, Youssef Chebli, Amir Jafari Bidhendi, Amir Sanati Nezhad, Colas Topszynski. All images are copyright protected and their use requires permission. To inquire about permission, please contact Dr. Geitmann.