Full sunlight is the best lighting condition for bean plant growth. The energy drawn from the sun maximizes the plant's fruit yield. Plants grown in full sunlight produce more beans.
Under shady conditions, bean plants develop larger leaves and taller stems. The plant needs a larger leaf surface area and a taller stem to increase the amount of light it can capture for photosynthesis. The energy expended making bigger leaves and longer stems reduces the amount of beans the plant produces.
Bean plants grow indoors where there is plenty of natural light. The conditions are similar to shaded outdoor areas and have similar effects on the plant growth. Less light also causes the plant to be less green than one grown outdoors in full sun.