The Effect of Photoperiod Duration Upon the Respiratory Activity of the Roots of Wheat Seedlings

Abstract

The root respiration rate of wheat seedlings was continuously measured (in terms of CO2 output) in a controlled environment. The effects of varying photoperiods of high intensity light, incident on the leaves, upon the rate of root respiration were studied. It was demonstrated that increases in root respiration rate occurred in response to the light treatments. The fluctuations in root respiration rate, induced by the photoperiods used, had a pattern over the 24-hr cycle, which included two peaks-when the photoperiod was of 6 or 12 hr duration. These henomena are discussed in relation to the hypothesis that root respiration rate fluctuates in response to a varying flow of assimilates from the leaves to the roots. No evidence was obtained of an endogenous (or circadian) rhythm of root respiration rate.