Phyllotactic Patterns in Some Members of the Vitaceae

Abstract

Changing phyllotactic patterns are found in some members of the Vitaceae such as Vitis riparia and Vitis cv Vivant. In addition to two opposite cotyledons, germinating seedlings of V. riparia and cv Vivant display two other phyllotactic patterns: (1) immediately following the emergence of the cotyledons, leaves are initated individually in a spiral pattern, usually 2/5, (2) upon the initiation of the first tendril the phyllotactic pattern changes to alternate and opposite leaves (distichous) with leaf-opposed tendrils at two consecutive nodes out of three. This study documents the different phyllotactic patterns occurring in these seedlings, concentrating on the transition between spiral and distichous leaf arrangements. The mean divergence angle observed at the primordial level in young seedlings of V. riparia and cv Vivant with spiral phyllotaxy was different from the reported divergence angle of 144⚬ (2/5) observed between mature leaves. The measurement of divergence angles can therefore differ greatly at different levels of observation (primordial vs. mature structure). The transition between spiral and distichous leaf arrangement is abrupt, the first tendril being initiated opposite a leaf. Later in development, the tendrils are shifted to one side of the axis giving the shoot a dorsiventral symmetry. The distichous "mature" dorsiventrally symmetrical pattern in seedlings of V. riparia and cv Vivant was compared to other members of the Vitaceae, which did not show this striking dorsiventrality.