Why Do the Cells of Plant Roots Generally Lack Chloroplast?

Chloroplast Function

• Chloroplasts are tiny organs living inside most plant cells. Within these organelles are multiple folds, similar to a human's small intestine. These folds hold chlorophyll, the green pigment that gives plants their signature appearance. As sunlight strikes the plant, chloroplasts harness its energy, absorb carbon dioxide from the atmosphere and, in conjunction with water from which oxygen is released, create sugars for the plant's growth and reproduction.

Darkness and Plant Development

• Roots remain in darkness for their entire life cycle. If your plant produced chloroplasts for the roots, they would provide no energy production. All plants conserve energy so that they can use all of their resources for vegetative and reproductive growth. By concentrating their chloroplasts on the aboveground section, plants maximize their photosynthesizing abilities for successful competition with surrounding species. For example, a plant's vigorous aboveground growth provides easy access to sunlight energy instead of its being crowded out by competing plants -- taller species may shade the struggling plant when it needs full sunlight.

Root Structure

• Roots have a completely different growth objective: They spread out to physically support the towering plants as they find nutrients and moisture for sustenance. Roots use tiny extensions, called root hairs, to move nutrient and water molecules between the soil and plant. Because roots must use all of their surface area for absorption, chloroplast production is not possible. Typical root growth often dives as deep as 3 feet for maximum absorption possibilities -- plants cannot waste energy on other cellular formations, or they might not survive in competitive locations.

Roots as Nutrient Storage

• The lack of underground chloroplasts allows the roots to act as storage facilities for the proteins, carbohydrates and sugars produced aboveground. Sugars produced in the leaf chloroplasts move down the stem and into the roots for storage; plants do not use all of their photosynthesizing energy immediately at the leaf level. Cloudy or stressful conditions for plants encourage them to use the stored energy to avoid wilting and permanent damage until more photosynthesizing is possible.