An Investigation of Shoot Interactions in Mercurialis Perennis L., A Rhizomatous Perennial Herb

Abstract

The development of shoots in populations of the perennial woodland herb M. perennis L. was investigated and the results compared with those obtained from other studies of plant populations. Whereas the numbers in populations of discrete individuals decay exponentially, the shoot populations of M. perennis decay in linear fashion. Although significantly fewer small shoots than large shoots survive late into the growing season, there is also high mortality among the largest shoots in the population. Although the relationship between mean shoot weight and density conforms to the competition-density equation (as do the relationships between mean weight of parts of shoots and density), the shoots do not conform to the -1.5 power equation through time. This is a result of low mortality of shoots during the light phase when growth is rapid, and little change in shoot weight during the shade phase, when mortality is higher. A model graph is presented to illustrate the relationship between mean shoot weight and density through time. Available evidence indicates that the power equation does not fit the development of parts of a rhizomatous perennial herb. Weight skewness does not progressively increase through the growing season and there is no indication that the level of skewness is related to shoot density. Log-normality is not approached and many skewness values decline after development of the tree leaf canopy.