Measurement of plant architecture in seven aquatic plants

We quantified architectural characteristics of seven aquatic macrophytes by measuring spatial complexity and shading properties. The plants were: Egeria densa, Hydrilla verticillata, Myriophyllum spicatum Potamogeton nodosus, Potamogeton pectinatus, Vallisineria americana, and Zosterella 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 plant species. Spatial complexity was calculated by adding the ratio between interstices frequency and size from both vertical and horizontal axes. Mean density and size of plant interstices differed significantly among plant species (x(2) = 123, df = 6, P < 0.01) and were greatest along horizontal axes. Plant complexity was lowest in M. spicatum and highest in P. pectinatus. Shading properties were significantly different among plants (x(2) = 40, df = 5, P < 0.01), and significant inter- and intra-plant strata differences were noted.