Phyllotaxy of maize
--Bird, RMcK

In yet another way maize is different from the usual plant -- the phyllotaxy of the alicoles of its ears does not follow the Fibonacci series. The leaves of most higher plants fall into 2, 3, 5, 8, 13, 21, etc. ranks along the stem where there is one leaf per node or 4, 6, 8, + ranks for opposite or whorled phyllotaxies. Maize ears, however, have ranks (stachys) of every number from 3 to 16 or more, switching, as rank numbers increase, between whorled, even-numbers of ranks and spiral, odd-numbers of ranks with single alicoles per node.

By clearing the glumes from sweet-corn cobs after dinner, marking the spikelet pairs and trying different spiral patterns, I found one rule governed all: alicoles two ranks apart are linked in a spiral or a whorl. Thus, on a cob with seven ranks (14 kernel rows), one follows the rule in a spiral going twice around the cob passing through seven contiguous nodes to reach the next alicole in the same rank, a "2/7" phyllotaxy. On a cob with eight ranks, one finds alicoles two ranks apart are linked in a whorl of four, and the next whorl of four is offset by one rank. I have never seen a 3/8 phyllotaxy in maize.

Of course, this is not the full story. While cobs with even numbers of ranks have ranks which parallel the axis, those with odd numbers have slightly spiraled ranks meaning that a phyllotaxy such as 2/7 really needs to be defined by a number like 21/77. But that's another study, as is the morphogenetic basis of this phenomenon. 


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