Why do seedlings kept in the dark produce tall, weak shoots and tiny yellow leaves?

Seedlings kept in the dark experience a condition known as etiolation, which causes them to grow tall and weak as they stretch toward any available light source. In the absence of sunlight, these plants do not have the necessary light for photosynthesis, which is the process that allows them to convert light energy into chemical energy. Without this crucial energy source, they cannot produce the chlorophyll needed for healthy green leaves, resulting in the tiny yellow leaves observed. The tall, spindly growth is a survival response; the plant is attempting to reach light to begin photosynthesis. However, this rapid upward growth compromises its structural strength, making the shoots weak and likely to fall over. This phenomenon is a direct result of the plant's effort to find light, but without the energy and nutrients from sunlight, the seedlings cannot thrive.