Methodology and Terminology for the Measurement of Light in Weed Studies—A Review

Abstract

Definitions and properties of light, the effects of light on plant growth and physiological processes, and methodology and terminology for the measurement and reporting of light are reviewed. Alternatives to photometric methods now generally used in studies of the effects of light on plants in weed research are proposed. For studies of leaf energy budgets and plant water relations, the irradiance may be appropriately measured with radiometric methods and the data reported as W [watts] m-2. For studies of photosynthesis, the photosynthetic photon flux density may be measured and the data reported as μE [einsteins] m-2s-1or μmol [μmoles of photons] m-2s-1. Different types of instruments are described and sources for these instruments are provided.