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Effects of Elevated Atmospheric CO2 on Micro-Propagated Grapevines Transferred from In Vitro to Ex Vitro Conditions
Reference
Carvalho, L.C., Esquivel, M.G., Martins, I., Ricardo, C.P. and Amancio, S.  2005.  Monitoring the stability of Rubisco in micropropagated grapevine (Vitis vinifera L.) by two-dimensional electrophoresis.  Journal of Plant Physiology 162: 365-374.

Background
Plants cultured in vitro typically suffer from a number of physiological and biochemical impairments, such that upon transfer to ex vitro conditions they often experience severe oxidative stress.  Hence, the authors conducted a study to see to what extent this stress might be alleviated by a nominal doubling of the air's CO2 content.  More specifically, they evaluated the damage done to the large subunit of Rubisco in grapevine (Vitis vinifera L.) plantlets while exposed to in vitro conditions and the degree to which that damage was ameliorated by atmospheric CO2 enrichment during subsequent exposure to ex vitro conditions.

What was done
In vitro plantlet cultures were maintained in a growth chamber at a photon flux density (PFD) of 45 Ámol m-2 s-1, after which they were transferred to ex vitro conditions having a PFD of either 150 (low light) or 300 (high light) Ámol m-2 s-1 and an atmospheric CO2 concentration of either 350 (low CO2) or 700 (high CO2) ppm.  Concurrently, a number of physiological and biochemical measurements were made on the plantlets at seven-day intervals over a period of 28 days.

What was learned
Rubisco degradation products were observed in the leaves of plantlets in both in vitro and ex vitro conditions.  However, as the authors report, "under low CO2 they were maintained for almost all of the 28 days of the acclimatization period, while becoming scarcely detected after 14 days under high CO2 and after 7 days when high CO2 was associated with high light."  In addition, they note that "patterns of soluble sugars in acclimatizing leaves under high light and high CO2 also gave an indication of a faster acquisition of autotrophic characteristics."

What it means
Carvalho et al.'s results demonstrate the beneficial impact of high CO2 concentrations in reducing the oxidative stress induced by the transfer of in vitro-produced plantlets to ex vitro conditions, as they state that "a net benefit from high CO2 treatments was clearly visible, contributing to an increased stability of Rubisco," and that "the disappearance of Rubisco large subunit degradation products in persistent leaves subjected to the ex vitro treatments may be considered an indicator of recovery from stress."

Reviewed 3 August 2005