African Wildlife & Environment Issue 83

FAUNA, FLORA & WILDLIFE

coming up the xylem from the roots - AND THIS ALL ON THE SAME TREE. At the time, in my garden, I noticed a Clivia inflorescence-stem that clearly demonstrated, visibly, how nutrients can be partitioned to the developing fruit – clearly by some hormonal feed-back loop (but then I am not a plant physiologist).

secondary leaves than on primary leaves. JUST for info the axillary leaf (middle one) also has a more grooved petiole and even rachis; with only a small petiolar ENF and possibly vestigial ones on the rachis between the pinna pairs – that are NOT exactly opposite either! All this shows that when one starts to go into minute detail there is too much information (I think) for most readers. In my view the separation and identification of PRIMARY and SECONDARY leaves is hugely important, not just to aid in identification but also ecologically! More of that later when I outline the nutritional difference between them as well as biomass per node differences… But first I want to outline what I have gleaned from my travels, focussing on how A. karroo grows, enabling it to thrive under a range of different environmental circumstances. Because from this knowledge I believed I could learn more about how A. karroo has evolved to survive, specifically in the semi-arid Karoo Bushveld. My journey to understand the growth and survival strategies started serendipitously when I was in the gym some years ago, looking out at a grove of planted A. karroo trees from the first floor window. The biggest tree, right next to the building, caught my eye as I noticed that the two major branches, about 1.5 m from the ground, were not the same diameter – one was almost double the size of the other (~200 mm versus ~120 mm). From past experience I had observed that when saplings branch into two that the branches start off at more or less the same diameter, but as they grow one often dominates the other. Looking down on this tree over the months, I noticed that the canopy from the BIG branch produced many more inflorescences and therefore pods than the ‘RUNT’ branch-canopy – and that was understandable, considering the size dichotomy. But what intrigued me more was that the ‘runt’ part of the canopy had many more, and bigger, spines, AND that the new shoots were much shorter than on the big branch. Clearly the big branch was getting much more than a fair share of water and nutrients

Photograph of my Clivia showing the end of the inflorescence stalk with the old flower pedicels, two of which developed fruits Note the fruit on the left was starting to abort, while the one on the right is clearly healthy. Note too that the healthy one was still being fed; evidence from the right-hand side of the main inflorescence axis being a healthy green while on the left the same stem it is yellowing and even dying on the extreme left. This to me is clear visual evidence showing that the plant is partitioning resources to the side that is still going to produce a ripe fruit with viable seeds. I submit that my ‘gym’ A. karroo , with the dichotomous branches of different sizes, was doing much the same thing. To me this indicates that if a part of an A. karroo tree, or possibly a whole tree, is nutrient starved it grows less and produces more spines.

28 | African Wildlife & Environment | Issue 83 (2023)