Ishii, K., Hosoi, Y. and Maruyama, E. 2008. The effects of carbon dioxide on rooting of woody plants. Propagation of Ornamental Plants 8: 144-147.
What was done
The authors investigated the effects of enriching the air with CO2 to just under 1000 ppm on the rooting of branch cuttings of two flower cherries (Prunus incisa and Prunus jamasakura), one endangered five-needle pine (Pinus armandi var. amamiana), seven nematode-resistant clones of Pinus densiflora and three nematode-resistant clones of Pinus thunbergli, as well as Pistacia chinensis.
What was learned
Ishii et al. report that "after two months of cutting, flower cherries were all dead in the normal CO2 condition." However, they found that "surviving rate in the CO2-enriched atmosphere was 92% and 75% for Prunus incisa and Prunus jamasakura, respectively," while "rooting rate was 8% and 33% with each species, respectively," but, again, "only with CO2 enrichment." In similar fashion, they note that "after six months of cutting in Pinus armandii var. amamiana with CO2 enrichment, rooting was observed in three out of eighteen branches of I-19 adult tree and in one out of twelve branches of I-12 adult tree while no rooting appeared without CO2 enrichment." And they report that "four out of twenty-one branches of Pistacia chinensis were rooted under carbon dioxide enriched condition after four months cultivation while no rooting was observed in the control." Only in the case of the nematode resistant pines were there "no clear effects of CO2 enrichment on the survival of cuttings."
What it means
The three researchers conclude their report by speculating that elevated atmospheric CO2 was effective for the survival and rooting of the majority of the cutting branches "because of its promoting photosynthetic activity in plants and possible synthesis of root promoting factors." Whatever the reason, their observations certainly suggest that atmospheric CO2 enrichment might well figure prominently in propagating commercially-important woody plants in the not-too-distant future.