Dear Editor:

TOP Dear Editor:

The recent article "Why Leaves Turn Red in Autumn. The Role of Anthocyanins in Senescing Leaves of Red-Osier Dogwood" (Feild TS, Lee DW, Holbrook NM [2001] Plant Physiol 127: 566-574) provokes me to write in protest, yet again, about the illogical and teleological propensities that continue to infect our science. The proper answer to the question posed is simply that some leaves turn red because in the course of their development, red pigments are produced as chlorophyll is declining. But this is not what the authors mean by the question. They wish to have an answer that provides a "reason" for the reddening and assume, at the outset, that the outcome must be some benefit to the plant. In essence, they propose that, fully aware of the effects of accessory photosystem II photon efficiency, the exposed leaves of the plant deliberately produce red pigments in order to reduce light absorption by the chloroplasts. This, in turn, by tortuous speculation, is supposed to result in greater recovery of N from the senescing leaves (although no such evidence is provided).

However, I am not so much concerned here with the experimental results or the conclusions. Rather, I wish to challenge again the anthropomorphic proposition that implies in one way or another, and however delicately or indirectly, that plants have the ability to plan their structure and even destiny. This is the teleological trap that I have discussed previously (Beevers H [1993] Annu Rev Plant Physiol 41: 1-12) and which others allude to much earlier. The continued references to all manners of "strategies" in plantsstrategies of phloem loading, of pollination, of defense against disease, and even the absurdity of evolutionary strategiesall imply that deliberate choices designed for a successful outcome have been made by plants.

It is of course perfectly reasonable to inquire whether the reddening of particular leaves confers on them any functional advantage over others not so endowed, but to suggest, for a moment, that the leaves redden to protect themselves from a potential danger is, I submit, indefensible.