Germination of a Green Bean Seed

Germination Requirements

• The bean seed requires a period of dormancy before germination. A seed taken from a fresh bean pod must be dried out before planting. Watering the planted seed leaches away abscisic acid, a germination inhibitor that prevents the seed from growing in advance of its correct photoperiod. Without the inhibitor, a seed may be tricked into growth during an autumn or winter warm spell and fail to survive. Adequate temperature, water, oxygen and light make seed germination possible.

Germination Begins

• A bean seed will germinate without soil if you place it on a bed of absorbent cotton and place it in a container on a sunny windowsill. This is a good way of observing the process of germination to see what normally occurs underground. The primary root grows through the seed coat first. The hypocotyl emerges next and pushes above the soil in the shape of an arch. The double cotyledons protect the plumule and first leaves from damage as they break through.

The Role of Light

• Red light, absorbed by phytochrome and blue light, absorbed by cryptochrome, trigger the straightening of the hypocotyl arch so that it reaches upward toward the sun. The cotyledons spread apart to reveal the plant's first two primary leaves. The cotyledons feed the developing plant until enough leaves have grown to begin food production through photosynthesis. The cotyledons also turn green as chlorophyll within them help the leaves to make more food. Eventually, the cotyledons drop off, leaving the leaves to continue food production on their own.

Germination Indoors and Outdoors

• Indoor germination requires that you soak the bean seeds to soften the seed coats and leach out existing germination inhibitor before placing the seeds in a container lined with a bed of absorbent cotton. Water the seeds once a day for a week and watch the transformation from dormant seeds to young plants. Outdoor germination is possible with adequate sunlight and once the danger of frost passes. Plant your seeds at a depth of 1 inch to aid the emergence of the hypocotyl arch.