Some Effects of Temperature and Substrate Content upon Respiration and the Carbon Balance of Field Beans (Vicia faba L.)

Abstract

The effects of substrate content and temperature upon the production of carbon dioxide in the dark were investigated in Vicia faba and Sorghum vulgare, using the time courses for carbon dioxide release. No endogenous rhythms were found. With V. faba at high substrate contents, a steady rate of respiration was measured at low temperatures, suggesting that the rate of respiration is limited by a third factor such as enzyme activity. This steady rate eventually decreased rapidly. There was a first order rate of decrease with time at higher temperatures. Low substrate contents gave a complex decay. The rate of decrease of the rate of respiration was affected by the initial state of the plants over the same range of rates. Reasons for this are discussed. The temperature sensitivity of respiration was investigated. The respiration of plants with high substrate contents had a lower temperature sensitivity than those with low substrate contents. This was further investigated by measuring the stoichiometry of carbon dioxide production in the dark from total soluble carbohydrate (as hexose equivalent). It is likely that incomplete hexose respiration, which occurs at high substrate contents, is less temperature sensitive than complete hexose respiration or the respiration of some other substrate.