Sunday, June 20, 2021

Amorphophallus leaf mystery explained

Descriptions of Amorphophallus have always emphasized that the leaves emerge from its corm one at a time, with a leafless resting period between leaves. This description is technically incorrect because it goes against the fundamental theory in plant morphology that leaves are lateral organs that arise from the side of a shoot. A shoot grows out of a bud and consists of a central stem bearing leaves on its sides (i.e. laterally) and terminating in an apical bud. Leaves cannot come straight out of a corm without being part of a shoot. The mystery was resolved in the Secret Garden of 1 Utama when new leaves were seen to be actually part of a shoot system in which two or more bracts precede the leaf. My interpretation is that a bud develops on the top of the corm, which develops into a highly condensed shoot that bears one or two sessile bracts (reduced leaves without stalks) followed by one giant leaf . As the leaf develops the bracts break up and wither away while the apical bud becomes permanently dormant. The shoot is then left with one giant leaf.

The photograph shows a cluster of  four shoots, arising from one large corm. In three of the shoots the  bracts have disappeared. One shoot is new, with its leaf just becoming visible above a bract that will soon wither away. I expect that eventually the corm will produce only one shoot at a time, each shoot represented by a single leaf. The ground cover in the picture is Arachis pintoi.


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