Kenneth L. Koonce

Solar energy conversion efficiency and growth aspects of the duckweed, Spirodela punctata (G. F. W. Mey.) Thompson

Abstract Duckweed, Spirodela punctata (G.F.W. Mey) Thompson, was grown on cattle manure dilutions in small outdoor tanks, under different environmental conditions, during the autumn of 1979 and the spring of 1980. Daily growth rates and solar energy conversion (photosynthetic) efficiencies of duckweed were similar for plants grown on manure dilutions of 2.5, 5.0 and 10.0 gl −1 . There were no significant differences in the daily growth rate or efficiency of photosynthesis for growth periods of 1–4 days. The maximum mean growth rate and solar energy conversion efficiency observed were 12.7 g m −2 day −1 and 4.2% of the photosynthetically active radiation (PAR). The highest values obtained for a single sample were 19 g m −2 day −1 and 4.9%. In terms of dry organic matter production, duckweed was observed to grow as much, or more, during the night as during the day. The source of energy for night growth was not determined. Percent moisture of the duckweed was less at high air temperatures than at low temperatures. Insolation was not significantly related to percent moisture. Percent ash remained relatively constant for all levels of temperature and insolation.

Estimation of components of variance for partially cross-classified data in a factorial arrangement of treatments

A procedure is presented for obtaining estimates of components of variance for the main effects and interaction in a two-way factorial arrangement of treatments with only partially cross-classified data (sometimes referred to as unbalanced data in a two-way crossed classification model with interaction). The procedure entails the use of two hierarchical analyses of variance in which each main effect is first treated as classes and then as subclasses. The estimation of the variance component for each main effect results from the solution of two simultaneous equations with values used obtained directly from the hierarchical analyses. The interaction component of variance can be obtained from the variance components for main effects. An example is presented for the purpose of illustrating the procedure. Interpretation of the interaction variance component estimated by the method is limited due to the absence of some of the subclasses.