Effects of atmospheric CO2 enrichment on the growth and development of Hymenocallis littoralis (Amaryllidaceae) and the concentrations of several antineoplastic and antiviral constituents of its bulbs.

Two 2-yr crops of tropical spider lily (Hymenocallis littoralis) plants were grown in field soil in clear-plastic-wall open-top enclosures in the Sonoran Desert environment of central Arizona. Half of the plants were exposed to ambient air of 400 ppm atmospheric CO(2) concentration and half of them were exposed to air of 700 ppm CO(2). This 75% increase in the air's CO(2) content resulted in a 48% increase in aboveground plant biomass and a 56% increase in belowground (bulb) biomass. It also increased the concentrations of five bulb constituents that have been demonstrated to possess anticancer and antiviral activities. Mean percentage increases in these concentrations were 6% for a two-constituent (1:1) mixture of 7-deoxynarciclasine and 7-deoxy-trans-dihydronarciclasine, 8% for pancratistatin, 8% for trans-dihydronarciclasine, and 28% for narciclasine, for a mean active ingredient percentage concentration increase of 12%. Combined with the 56% increase in bulb biomass, these percentage concentration increases resulted in a mean active ingredient increase of 75% for the 75% increase in the air's CO(2) concentration used in our experiments.