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Elevated CO2 and the In Vitro Propagation of Walnut Microshoots

Paper Reviewed
Vahdati, K., Asayesh, Z.M., Aliniaeifard, S. and Leslie, C. 2017. Improvement of ex vitro desiccation through elevation of CO2 concentration in the atmosphere of culture vessels during in vitro growth. HortScience 52: 1006-1012.

Growth conditions during conventional in vitro plant propagation often affect survival rates following transfer to ex vitro environments. Photosynthesis of in vitro plantlets, for example, can often be restricted due to low CO2 concentrations in the headspace of the culture containers. Additionally, low CO2 concentrations and high relative humidity tend to promote an enduring open stomatal state, inhibiting water retention in plantlet leaves after transfer to an ex vitro state. However, given the known impacts of high CO2 concentrations on stomatal morphology and its associated benefits on plant water use efficiency, Vahdati et al. (2017) set out to see if they could improve the survivability of ex vitro walnut microshoots by increasing the CO2 concentration of the air surrounding plantlets during in vitro propagation.

The experiment was conducted by growing Persian walnut (Juglans regia, cv. Chandler) microshoots in vitro under low and high CO2 concentrations in a controlled environment for 30 days. At the end of this period, the plants were removed from their cultures and a number of measurements (stomatal features, transpiration rate, relative water content, etc) were made during ex vitro desiccation.

In discussing their findings, Vahdati et al. report that "exposure to increased CO2 concentration resulted in [the] generation of more small-sized and fewer large-sized stomata," which alterations caused a decrease in plant transpiration rates. Consequently, walnut microshoots in the elevated CO2 environment experienced "improved control of water loss during [ex vitro] desiccation." Vahdati et al. also report that there were "no negative effects [of high CO2] on plantlet vegetative characteristics. And in light of these combined findings, they conclude that "increasing CO2 concentration during in vitro culture of walnuts can be a useful tool to reduce ex vitro water loss in a species that is particularly sensitive to desiccation during ex vitro acclimation."

Posted 8 February 2018