Answer:
1. About 10^-6
2. The growth of roots is regulated by auxin concentration, with concentrations greater than resulting in smaller roots. Concentrations lower than 10^-8.5 encourage roots to develop more as concentrations increase, up to a concentration of 10^-8.5.
3. Auxin, I would apply at a concentration of around 10^-8.5 to generate the biggest carrot roots.
Step-by-step explanation:
Auxins are growth hormones that are found in root tips and shoots, causing the roots to grow bigger as concentrations rise and causing the carrots to grow larger.