Answer: The herbicide (weed killer) takes away a plant's ability to get carbon dioxide. This causes the plant to not be able to produce glucose a source of energy for the plants. Even if there are plenty of water, sunlight, and chloroplasts, the photosynthesis process won't be complete without carbon dioxide. Once in the soil, herbicides can suffer alteration in their structure and composition, due to the action of physical, chemical, and biological processes. This action on the herbicides is the one that will determine their activity and persistence in the soil. Plants damaged by soil sterilant herbicides are the least likely to recover. Plants that show signs of growing out of the problem will likely recover. Plants that appear to lose vigor may not. The survival of damaged plants can be increased by reducing other stresses.