Towards the end of his life, Charles Darwin, “assisted by” his son, Francis, wrote several books on plants including “The Power of Movement in Plants” published in 1880. The father and son team performed many experiments on plants, and observed that they exhibit a range of sophisticated behaviors but at a much slower pace than animals – a controversial conclusion at the time but one that is now largely accepted. For example, stem cells at the very tip of the root tip (pictured here in the lower center of the image) employ a combination of developmental processes including cell cycle control, cell division, cell polarity and cell elongation in order to form roots capable of an array of complex behaviors including gravitropism, hydrotropism, hormone signaling and communication with other plants.
How do scientists collect images of living root tips that grow downwards in response to gravity, and most microscopes require the specimen to be in a horizontal position? One novel solution is to turn the microscope on its side, and use a vertical specimen stage so that the young plants can grow normally upright in the microscope. In addition, they have developed a unique method of illuminating the plants for experimental manipulations and a computer-based tracking system that enables them to study the fine details of root growth over very long time periods. In this study, Arabidopsis thaliana plants were genetically labelled with a plasma membrane marker (in green) and a nuclear marker (in purple), and their root tips were imaged using time-lapse in a vertically mounted confocal microscope. The growing root tips were tracked using the custom-built “TipTracker” MATLAB® program that allows the microscope to follow the growing root tip.
Daniel von Wangenheim, Robert Hauschild, Matyáš Fendrych, Vanessa Barone, Eva Benkova and Jirí Friml, Daniel von Wangenheim, Ph.D., Developmental and Cell Biology of Plants, Institute of Science and Technology, Austria