Living plant systems: how robust are they in the absence of gravity?

Reflections on 'plant neurobiology'

Plant neurobiology, a new and developing area in the plant sciences, is a meeting place for scientists concerned with exploring how plants perceive signs within their environment and convert them into internal electro-chemical ('plant neurobiological') signals. These signals, in turn, permit rapid modifications of physiology and development that help plants adjust to changes in their environment. The use of the epithet 'neurobiology' in the context of plant life has, however, led to misunderstanding about the aims, content, and scope of this topic. This difficulty is possibly due to the terminology used, since this is often unfamiliar in the context of plants. In the present article, the scope of plant neurobiology is explored and some of analogical and metaphorical aspects of the subject are discussed. One approach to reconciling possible problems of using the term 'plant neurobiology' and, at the same time, of analysing information transfer in plants and the developmental processes which are regulated thereby, is through Living Systems Theory (LST). This theory specifically directs attention to the means by which information is gathered and processed, and then dispersed throughout the hierarchy of organisational levels of the plant body. Attempts to identify the plant 'neural' structures point to the involvement of the vascular tissue - xylem and phloem - in conveying electrical impulses generated in zones of special sensitivity to receptive locations throughout the plant in response to mild stress. Vascular tissue therefore corresponds, at the level of organismic organisation, with the informational 'channel and net' subsystem of LST.