The goal of the Pickard laboratory is to work out how plants sense mechanical stimuli and how mechanoresponses help the plant. Toward this end, the lab has developed specific inhibitors for two responses (gravitropism and thigmotropism), described mechano-sensory Ca2+ channels sensitive to these inhibitors, and discovered a plasmalemmal reticulum that links cytoplasmic structures to the cell wall. The reticulum, pictured to the right, controls cellular rise of Ca2+. Treatment with the inhibitors confirms that the rise is mediated by the mechanosensory channels.

These findings open up many questions. For example, the rise of cell Ca2+ is highly patterned and clearly depends on elaborate transmission mechanisms. What are they? Large cytoplasmic rises lead to large nuclear rises. Do these promote protein synthesis? In particular, the mechanosensory channel activity is enhanced by chilling, known to activate synthesis of cold-regulated proteins. Is such regulation mediated by channel activity? The existence of the plasmalemmal reticulum suggests that the classic model for guidance of cellulose deposition by microtubules is far too simple. Does the reticulum have a dynamic geometry which could help control deposition? The most interesting reticulum and channel responses may be those too small to trigger elevation of Ca2+ throughout the cell. Do these contribute to local control in processes such as growth and gravity sensing?

If Ca2+ channels play a role in gravity sensing, at what level in the reaction web? This lab has shown that sensing consists of two primary processes, one facilitative and one vectorial. Combining these provides the plant flexibility in determining whether its organs will grow vertically of at some oblique angle. Overlay of a third process permits horizontal growth. Dissection of these component processes clears the way for analysis of contributing reactions.

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Fluorochrome-tagged antibodies applied to a protoplast and visualized by computational optical sectioning microscopy point up the plasmalemmal reticulum.