ABSTRACT
Light quantity, light quality, and temperature are variables that follow reasonably predictable annual patterns which can provide "signals" to the growing plant to modify source-sink relationships. Growing plants sense various components of their constantly changing environment and adapt by regulating source-sink relationships to favor survival as they proceed through their life cycles from seed germination to production of the next generation of seed. Overcast weather results in a decreased quantity of light and can influence plant development. Corn seedlings were started and grown for several weeks in plant spacing and row orientation studies in which light spectra were recorded and plants were measured for leaf length and width, leaf area, stem length, and biomass allocated to leaves, stems, and roots. The sun and shade leaves in each of these examples developed in and adapted to differences in both light quality and light quantity.
