MEASUREMENT OF PLANT ARCHITECTURE IN 7 AQUATIC PLANTS

We quantified architectural characteristics of seven aquatic macrophyt es by measuring spatial complexity and shading properties. The plants were: Egeria densa, Hydrilla verticillata, Myriophyllum spicatum Potam ogeton nodosus, Potamogeton pectinatus, Vallisineria americana, and Zo sterella dubia). Two replicates of each plant were cultured in aquaria in concrete raceways. Light transparency and vertical and horizontal interstices measurements were taken at three strata level in each plan t species. Spatial complexity was calculated by adding the ratio betwe en interstices frequency and size from both vertical and horizontal ax es. Mean density and size of plant interstices differed significantly among plant species (x(2) = 123, df = 6, P < 0.01) and were greatest a long horizontal axes. Plant complexity was lowest in M. spicatum and h ighest in P. pectinatus. Shading properties were significantly differe nt among plants (x(2) = 40, df = 5, P < 0.01), and significant inter- and intra-plant strata differences were noted.