Energy partitioning in terrestrial orchids—a model for assessing their performance

A model of the within-season growth of terrestrial orchids is presented. The model predicts the size of the tubers of Dactylorhiza majalis and Dactylorhiza fuchsii. Therefore, destructive methods can be avoided when sampling these rare orchids. The correlation coefficient and the slope of the relation between two consecutive measurements of leaf area early in the season are good indicators of plant performance. The average tuber size is indicated by the correlation coefficient and the maximum photosynthetic activity of the plants by the maximum slope of this relation. Data are presented on the seasonal growth of leaves and inflorescence of D. majalis. This was obtained by monitoring the above ground growth of a large number of individual plants. The model predictions are compared with empirical data from the literature and new data.