Turkish Journal of Botany




The influence of aging processes on respiration and the ratio of respiratory pathways in the leaves of Rhodiola rosea L. and Ajuga reptans L. under natural conditions was investigated. Young leaves had a higher respiration rate and higher activity of the alternative respiratory pathway than did mature leaves. The capacity of the alternative respiratory pathway did not show significant differences between the young and mature leaves of R. rosea and increased in the mature leaves of A. reptans (from 60% up to 88%). This fact may be explained by the higher requirements of growing tissues for metabolites. In this case, the alternative pathway could be responsible for the continuous activity of the citric acid cycle and glycolysis, and, therefore, deliver additional metabolites. The decline in activity of the alternative pathway with aging could be explained by the lower demand of the older leaves in metabolites. The high capacity of the alternative respiratory pathway in the mature leaves may be considered evidence of a high respiratory potential. We believe that this phenomenon may be explained by the fact that leaves are frequently confronted with numerous stress events during their life and, as a consequence, increase the respiratory capacity as a tool of stress resistance.


alternative respiratory pathway, respiration, alternative oxidase, leaves, age, Rhodiola rosea, Ajuga reptans

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