A Study of the Total Ultraviolet Exposure to All the Leaves for Small Plant Growth

A dosimetric spectrum evaluator was employed to evaluate the total biologically effective UV (UVBEplant) on the surface of all the leaves of small plants. It was applied to evaluate the UVBEplant to soybean leaves (Glycine max [L.] Merr.), cultivar Essex. The plants received three levels of UVBEplant averaged over all the leaves (0, 8.1 and 15.8 J cm) from emergence to the V7 growth stage. As canopy closure occurred with plant growth, the ratio of the average of the UVBEplant to all leaves compared to that on the uppermost set of leaves changed from 0.85 to 0.50 to 0.29 for the V2, V4 and V7 stages respectively. Measurement of the UVBEplant at the top of the canopy would introduce errors of 18%, 100% and 245% at the V2, V4 and V7 stages respectively compared to the actual exposure to the plant leaves. The evaluation of leaf UVBEplant allows formulation of models defining plant response such as suppression of plant height and leaf area in terms of the UV exposure to all the leaves along with the effects on the fresh and dry weights of the leaves, stems and roots.