Abstract
In leaves of Alocasia odora, a shade species, respiration rates were lower than those of sun species. These low rates are important for the carbon balance under low-light environments. In vivo activities of alternative oxidase (AOX) were also lower. AOX is not coupled to ATP production. Since the respiratory rates are already low, the low activity of AOX in A. odora leaves could optimise energy production. We analysed what biochemical mechanisms caused low AOX activity in A. odora leaves. A. odora leaves had a large quantity of AOX and most of the AOX protein in A. odora leaves was in the inactive oxidised dimer form under a low light environment. Under photo-oxidative conditions, AOX was found to be in the active reduced dimer form. We hypothesise that AOX prevents over-reduction of the respiratory chain under such an environment.
