In this paper we investigate the solutions of the equation in the title, where φ is the Euler function. We first show that it suffices to find the solutions of the above equation when m = 4 and x and y are coprime positive integers. For this last equation, we show that aside from a few small solutions, all the others are in a one-to-one correspondence with the Fermat primes.
CO2 and O2 exchange rates, chlorophyll fluorescence and P700 oxidation (absorption at 830 nm) were recorded in Helianthus amuus L. leaves grown in soil in a growth cabinet. Phase-portraits of CO2 exchange rate plotted against three other parameters were ušed to interpret control of electron transport during photosynthesis oscillations, initiated by transfer from air to the saturating CO2. Plots of the CO2 exchange rate vs. P700 revealed that the P700 part which remained oxidized was almost proportional to CO2 exchange rate during both the ascending and descending phase of oscillations.