Leaf size regularities in Festuca pratensis from the systemic viewpoint

Abstract

The influence of internal systemic factors on the size of fully grown leaves was investigated in the Poaceae plant Festuca pratensis. Using the systemic approach, the length of leaves of different ordinal numbers along a shoot and the length of leaves of the same ordinal number on different shoots were measured, analysing groups of shoots categorized as subsystems by the authors. It was found that the length of leaves regularly increased with an increase in the ordinal number of leaves along the shoot. The explanation could be systemic trophic relationships: the number of donor leaves increases, which expresses the shoot size factor, i.e. more assimilates are received by younger leaves, thus a vegetative developmental programme has been implemented. Another tendency was discovered as well: the length of the same numbered leaves also regularly increased with an increase in the shoot ordinal number. This increase is manifested in apical subsystems, while leaf length distribution in the basal subsystem is irregular. The explanation could be systemic informational relationships causing a spatial effect, i.e. apical dominance, as the energetically more important apical parts send a signal to suppress the growth of basal parts and ensure the flow of resources to the apical region. This set of internal systemic patterns is relevant for further research on environmental factors (nutrition, temperature, moisture, etc.), and controlled experiments could benefit by sampling leaves of the same internal systemic influence and by rejecting cases of irregular distribution.