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Carbon Dioxide Enrichment Propagates Success in Protea cynaroides

Paper Reviewed
Wu, H.C. and Lin, C.C. 2013. Carbon dioxide enrichment during photoautotrophic micropropagation of Protea cynaroides L. plantlets improves in vitro growth, net photosynthetic rate, and acclimatization. HortScience 48: 1293-1297.

Protea cynaroides, or King Protea, is a well-known woody shrub in the international floriculture industry, primarily prized for its attractive flower head that consists of hundreds of flowers. However, according to Wu and Lin (2013), of all the plants in the Proyeaceae family, "those belonging to the Protea genus are the most difficult to propagate in vitro (Olate et al., 2010; Rugge, 1995)." As a result, efforts have been expended to overcome this difficulty. Yet despite various advancements, they note that "shoot growth and leaf development of P. cynaroides explants in vitro remain very slow and inconsistent," adding that "attempts to promote vegetative and root growth during ex vitro acclimatization have achieved limited success."

Hoping to capitalize on some of the positive growth advantages associated with atmospheric carbon dioxide enrichment, Wu and Lin set out investigate the effects of elevated CO2 on the growth and development of P. cynaroides. Their experimental setup included growing P. cynaroides plantlets under four different CO2 concentrations -- ambient air (control), 1,000, 5,000, and 10,000 ppm CO2 for a period of either 45 days (in vitro) or 60 days (ex vitro) -- after which they measured various growth and developmental parameters of the plants.

Results of the in vitro portion of their analysis indicate that elevated CO2 produced a "higher number of leaves, larger leaf areas, longer shoots with higher shoot weight, and had greater photosynthetic ability," leading the two scientists to describe these plantlets as being of a "higher quality" than those cultured without CO2 enrichment. With respect to the ex vitro portion of their study, the Taiwanese researchers first note that the quality of plantlets produced in vitro is one of the key factors affecting their development and survival during the acclimatization, or ex vitro, period. And in this regard, they report that (1) the plantlets enriched with CO2 "survived better during acclimatization with improved root and leaf growth," such that (2) they experienced a survival percentage "at least four times higher than the control plantlets," plus (3) a nearly-doubled rooting percentage, and that (4) they formed at least twice as many new leaves. As a result, Wu and Lin conclude that "the high survival percentage and improvement in the overall growth of P. cynaroides during acclimatization was a direct result of CO2 enrichment and the promotion of photoautrotrophic growth in vitro."

Olate, E., Escobar, L.H., Sepulveda, C., Rios, C. and Errandonea. P. 2010. Advances and strategies for micropropagation of Proteaceae species. Acta Horticulturae 869: 157-164.

Rugge, B.A. 1995. Micropropagation of Protea repens. Acta Horticulturae 387: 121-127.

Posted 29 December 2014