Three weeks after we first called attention to the dying of parent leaves in the low-CO2 tanks and the accelerated growth of new-vine sprouts in the CO2-enriched biospheres, both trends continue.  In Tanks 1 and 2, six of the original seven parent leaves in each tank are dead, while in Tanks 3-6 only two of them, on average, have died.  In the case of new-vine sprouts, on the other hand, three have emerged above the gravel in Tank 1, four in Tank 2, five in each of Tanks 3-5, and seven (all of them) in Tank 6.

Figures 1-3 again report the results of new-vine sprout and primary and secondary root growth to date.  In viewing these graphs, one may perhaps wonder why, after rising dramatically from 108 to 125 to 250 ppm CO2, primary root length per plant rises no further and actually tends to drop a bit in progressing to biospheric airspace CO2 concentrations of 594, 882 and 1116 ppm.  One reason we have mentioned in the past is simply plant variability.  More likely, however, is the fact that root length does not tell the whole story.  Root thickness must also be considered.  In viewing Figures 4 and 5, for example, it can be seen that the original primary root of the left front plant from Tank 6 is somewhat thicker than the primary roots of the left front plant of Tank 3.  When we finally harvest the plants at the end of the experiment, our dry weight or biomass measurements will account for these differences … we think.  Experiments often humble one, however, when the real world hands down a verdict that is different from what you were sure it would be.  In viewing the totality of Figures 4 and 5, however, it is clear that even if primary root biomass levels off between Tanks 3 and 6, new vine biomass is much greater in the higher-CO2 tank, at least for these two specific plants.  So like opera and baseball, the experiment isn't over 'til its over!