Herbicides like 2,4-D and 2,4,5-T stimulate cell division. How might this fact explain why these chemicals are effective as herbicides?
This is because Herbicides like 2,4-D and 2,4,5-T are known as plant growth regulators or auxin herbicides. Auxin control cell growth by division or elongation therefore plants need auxin for adequate growth and development.
If in excess the growth will be over stimulated and if auxins are less then there will be no growth.
2,4-D and 2,4,5 kills broadleaf weeds as it is absorbed through the leaves and translocated through the plant meristems they make the cell divide and grow continuously leading to unsustainable growth causing stem curl-over and withering eventually leading to death of the plant.