Ontogeny of Asymmetry and Compensational Growth in Elm Ulmus glabra Leaves under Different Environmental Conditions

Levels of fluctuating asymmetry (random variation in size among sides) may be partly determined by compensational growth, and the efficiency of such compensation may be affected by stress. Here we provide the first test of this hypothesis by studying the effect of saline stress on the ontogeny of size and symmetry of leaf width in broad‐leaved elms Ulmus glabra. Leaves that developed on saline‐treated trees became more asymmetric with time but not significantly smaller than leaves on control trees. This saline effect resulted from an increase in the variance in ontogenetic trajectories. Serial autocorrelation in asymmetry between subsequent days was significantly more negative (i.e., indicating stronger compensational growth) in control than in saline‐treated trees. Leaves from saline‐treated trees took longer to develop than leaves on control trees. These findings indicate that ontogeny is disrupted by saline treatment, preventing or reducing compensational growth to constrain leaf asymmetry within the same boundary as in control trees.