Acta Horticulturae

The retarding effect of CO2 on senescence processes in leaves was studied by applying 10% CO2 to chervil bunches in a flow-through system. Since the senescence retarding effect of CO2 could be attributed to its action as a competitive ethylene inhibitor, the effect of CO2 on chervil leaf senescence in the presence (2000 μl/l) or absence of another ethylene action inhibitor, 2,5-norbornadiene (NBD), was studied. Results show that senescence processes (chlorophyll loss and lipid oxidation) were more effectively retarded in CO2- or CO2 + NBD-treated leaves, as compared with NBD-treated leaves. These results indicate that the senescence-retarding activity of CO2 cannot be solely attributed to its action as an anti-ethylene agent. Since high levels of CO2 would presumably affect internal pH, with the active species of CO2 hydration being HCO3- or H+, a possible mechanism for the ethylene-independent action of CO2 in delaying senescence through shifting of cellular pH, is suggested. CO2 treatment resulted in increase of the cell sap pH of chervil leaves by one pH unit during senescence. This increased pH was mainly due to retention of the original levels of polyamines in CO2- or CO2 + NBD-treated chervil bunches in the course of senescence. During this period, the level of polyamines decreased by 50% in control or NBD-treated leaves. It seems therefore that in addition to its anti-ethylene action, the senescence-retarding effect of CO2 operates through maintenance of the original levels of polyamines, which acted as senescence retardants in chervil leaves. This retention of polyamines, which are known as nitrogenous bases, may exhibit a possible mechanism for regulating the cytoplasmic pH as a response to the transitional cellular acidification by high CO2.

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Mode of action of CO2 in delaying senescence of chervil leaves
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Mode of action of CO2 in delaying senescence of chervil leaves

The retarding effect of CO2 on senescence processes in leaves was studied by applying 10% CO2 to chervil bunches in a flow-through system. Since the senescence retarding effect of CO2 could be attributed to its action as a competitive ethylene inhibitor, the effect of CO2 on chervil leaf senescence in the presence (2000 μl/l) or absence of another ethylene action inhibitor, 2,5-norbornadiene (NBD), was studied. Results show that senescence processes (chlorophyll loss and lipid oxidation) were more effectively retarded in CO2- or CO2 + NBD-treated leaves, as compared with NBD-treated leaves. These results indicate that the senescence-retarding activity of CO2 cannot be solely attributed to its action as an anti-ethylene agent. Since high levels of CO2 would presumably affect internal pH, with the active species of CO2 hydration being HCO3- or H+, a possible mechanism for the ethylene-independent action of CO2 in delaying senescence through shifting of cellular pH, is suggested. CO2 treatment resulted in increase of the cell sap pH of chervil leaves by one pH unit during senescence. This increased pH was mainly due to retention of the original levels of polyamines in CO2- or CO2 + NBD-treated chervil bunches in the course of senescence. During this period, the level of polyamines decreased by 50% in control or NBD-treated leaves. It seems therefore that in addition to its anti-ethylene action, the senescence-retarding effect of CO2 operates through maintenance of the original levels of polyamines, which acted as senescence retardants in chervil leaves. This retention of polyamines, which are known as nitrogenous bases, may exhibit a possible mechanism for regulating the cytoplasmic pH as a response to the transitional cellular acidification by high CO2.

Scientific Publication