Persistent Rhythms of O2-Consumption in Potatoes, Carrots and the Seaweed, Fucus.

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Abstract
The 02 consumption of each of these plants was determined hourly over continuous periods of at least 29 days. Each was found to possess a specific mean daily pattern when any possible mean lunar-day cycle was randomized; the three plants showed more similar mean lunar-day cycles when the daily cycle was randomized. The minimum rate in the lunar cycle occurred 1-3 hours before zenith, with a lesser minimum comparably before nadir. All three plants showed a maximum rate about 3-5 A.M.; the carrot showed a broad minimum about noon and a second maximum in the early evening, while Fucus showed a broad maximum about noon and minima about 7 A.M. and 8 P.M. The potato showed a steady drop in rate through the day with a lesser maximum in each of the remaining 3-quarters of the day. All plants showed a systematic fluctuation in the form of the daily cycle through a synodic month. The 5-6-7 P.M. rates showed an approximate inverse relationship with barometric pressure through the periods of observation and the hourly rates showed significant correlations with the concurrent rates and directions of hourly pressure change. The nature of a possible external stimulus, and also, the significance of the cycles for the plants are discussed.

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