intdots.gif (546 bytes)
white1.GIF (834 bytes)

Topical Tropical Fruit

By Robert C. Balling Jr., Ph.D.
Arizona State University

As you finish up the last of those holiday fruit baskets, take a moment to consider the healthful culinary splendor an enhanced carbon dioxide (CO2) world promises us.

Of course, we celebrated the mango's future just a few issues ago. Now, a review of numerous studies reports that a near-doubling of CO2 increased the dry weight of mango trees' old and new leaves and branches and roots. The dry weight of the total fruit increased by 18 percent—almost entirely in its flesh.

The article, by the University of Florida's Bruce Schaffer and several colleagues in Australia, explored the possibilities of several other fruits under elevated CO2 conditions, among them:

Avocado. Avocado plants increase their net CO2 assimilation significantly as the CO2 increases. The elevated CO2 increased the dry weight of leaves, new branches, trunks, and roots of the avocado plants.

Banana. Like the avocado plants, banana trees went bananas for elevated CO2 levels. Net CO2 assimilation in banana trees increased with higher concentrations of CO2, and following six months of CO2 enrichment (1,000 ppm vs. 350 ppm), the dry weight of the leaves increased by 131 percent, the root dry weight increased by 191 percent, and the total dry weight of the entire banana trees increased by 139 percent. The elevated CO2 more than doubled the size of the banana trees.

Macadamia. These Hawaiian delicacies went nuts for CO2 as it jumped from 350 ppm to 600 ppm, increasing the dry weight of new leaves, trunks, and roots.  Six months of elevated CO2 increased the dry weight of the husk, the shell, the kernel, and the total nut. The nuts were 25 percent bigger thanks to only six months of elevated CO2.

For subtropical and tropical fruit crops, Schaffer says:

Increased atmospheric CO2 concentrations [in amounts that] far exceed the anticipated rate of increase for the next 50 years appear to enhance carbon assimilation of subtropical and tropical fruit crops, provided there are no sink restrictions. Therefore, these species should benefit from predicted increases in atmospheric CO2 concentrations.

Which means more food for a hungry world, Schaffer explains:

Productivity of subtropical and tropical fruit crops should increase as a result of increased global CO2 concentrations.

CO2's largesse extends to all manner of flora:

Thus, a global increase in atmospheric CO2 concentrations should increase productivity of branched, woody, subtropical, and tropical species.

Exotic flavor, important vitamins, antioxidant protection—with atmospheric CO2 levels are on the rise, this new millennium may well be an era of eating better and being healthier!

Reference:

Schaffer, B., et al., 1999, Atmospheric CO2 enrichment, root restriction, photosynthesis, and dry-matter partitioning in subtropical and tropical fruit crops. Horticultural Science, 34, 1033–1037.