A Study on the Effect of Time in Plants

We are engaged in a continuing study concerning the effect of time on plants. The approach is to apply a common statistic, within-group variation in morphological integration, to plants of different age or subjected to different treatments in a search for common underlying patterns. Within-group variation in morphological integration is an estimate of the relationship among variables. Previous studies have shown that it increases with time, both in ontogeny and phylogeny, and also it is higher in grape leaves that develop in a higher energy environment. The clovers studied here add a period of time longer than ontogeny and shorter than phylogeny and thus expand the comparison of different aged plants. As with the effect of ontogeny or phylogeny, clovers collected from the oldest pasture (45 years old) had the highest within-group variation in morphological integration. This time-related change in within-group variation in integration is similar to that seen in grape leaves that grew in higher energy environments over a single growing season. Thus, it is tempting to consider these similar responses to time and energy as an argument for thermodynamics being the underlying cause of time-related changes in plants.