Plant Individuality: A Physiological Approach

While plants provide some of the most interesting cases for individuality-related problems in philosophy of biology (e.g., Clarke 2012; Gerber 2018), no work has examined plant individuality through specifically focusing on physiological processes, a lacuna this paper aims to fill. We think that different domains of biology suggest different approaches, and our specific focus on physiological processes, such as plant hormone systems and source-sink balance regulations, will help to identify coordinated systems at different scales. Identifying physiological individuals is crucial for a wide range of research in plant biology, including research on plant nutrition, transport and accumulation of nutrients in edible parts, and plant responses to various stress conditions such as plant diseases and changing abiotic conditions. Although plants do produce systemic responses to local stimuli (e.g., a sudden wound on one leaf can result in a whole-plant response), considering them as individuals is (often) problematic. They are highly modular organisms, and they can grow vegetatively, constituting clones of what seem, superficially, to be individual organisms. Moreover, as with animals, there are problems raised by their symbiotic relations to micro-organisms, most notably the mycorrhiza, through which they may be connected to other plants. We argue that coordinated plant systems can be distinguished at multiple scales from a physiological perspective. While none of these is a unit that must be necessarily called “the individual,” they offer integrated approaches for various research problems in plant science.