As a change of pace, we are this week presenting full views of the front of each tank.  Tank 2, shown in Figure 1, has the lowest experiment-to-date mean airspace CO2 concentration (105 ppm); and it can readily be seen that its plants have fared worse than those of all the other biospheres.  All of its original parent leaves are dead; and although four new-vine sprouts have emerged above the surface of the tank's gravel, about 20% of two of them have also died.

The plants of Tank 1 at 125 ppm CO2 (see Figure 2) have fared a little better, but not by much.  One and a third of this biosphere's original plant leaves are still alive (the two front leaves), and none of its three emergent new-vine sprouts has exhibited any signs of dying.  In addition, the left front plant has a slightly more extensive root system than both of the two front plants of Tank 2. Tank 3 at 256 ppm CO2 (see Figure 3) shows a vast improvement over both Tanks 1 and 2.  Only 1.7 of the original seven parent leaves have died; and of the five emergent new-vine sprouts, none shows any signs of dying.  Primary roots are also larger and more numerous; and good secondary root systems - which were totally lacking in Tanks 1 and 2 -- are beginning to develop. Tank 4 at 582 ppm CO2 (see Figure 4) appears not much different from Tank 3 at this juncture of the study.  It has slightly less total root length, but two of its primary roots look a little thicker than those of Tank 3.  In addition, there appears to be slightly more new-vine length in Tank 4; and although there are three more dead parent leaves than in Tank 3, Tank 4 has one more emergent new-vine sprout.  No matter how we squirm on this one, however, we cannot yet claim that the extra 326 ppm CO2 that Tank 4 contains above that of Tank 3 has done it much good yet.  But remember, the experiment's still far from over; and much of its results remain hidden in the gravel behind the black felt.  In fact, it is conceivable that some of the front plants of the tanks may have been able to send a root or two through the black felt material, which could also confound our results at this stage. Plant growth in Tank 5 at 873 ppm CO2 (see Figure 5) also is not too impressive at this point of the experiment.  New-vine length, in fact, is way down from that in both Tanks 3 and 4, although that of the five plants in the gravel behind the black felt may actually be slightly greater.  Secondary root growth, on the other hand, is clearly superior, being approximately twice as great in Tank 5 as it is in Tanks 3 and 4.  Tank 6 at 1107 ppm CO2 (see Figure 6) finally comes in with a better report than all of the other tanks, although not by a whole lot.  Only 1.2 of its original seven parent leaves are dead, all seven of its new-vine sprouts have emerged above the surface of the gravel, and none of them shows any signs of deteriorating.  Although its primary root length per plant is on a par with that of Tanks 3-5, some of its primary roots are thicker; and its secondary root length is much greater than that of Tanks 3 and 4. Last of all, its new-vine length per plant is slightly larger than that of all other tanks.