Anisophylly of Lateral Shoots

The inequality shown by anisophyllous leaves in plants withdecussate phyllotaxis can be measured as the difference in sizebetween the two leaves at a node, expressed as a percentageof their mean size. This is referred to as the degree of anisophylly. In Acer anisophylly of two types with different causation occurs.

1. 1. Primary anisophylly which is shown only by first year shootsdeveloped from axillary buds and which is due to the inequalityof the leaf primordia. Primary anisophylly is thus determinedby events occurring during the formation of the bud and is irreversible.
2. 2. Secondary amsophylly which is shown chiefly by the second(and subsequent) year's extension growth of lateral shoots frombuds which are isophyllous and which is due to the positionin which the shoot develops. This type of anisophylly is reversibleif the position of the developing shoot be changed.

Effects of secondary anisophylly may be superimposed on thoseof primary anisophylly. The recognition of these two causally distinct types of anisophyllyoccurring in one plant does much to resolve the apparently conflictinginformation available relating to lateral anisophylly.