Agar is a hydrophilic colloid, it is like a medium, but the gap is much smaller than a normal medium, it is transported like activated charcoal. It transports like activated charcoal, only the object of absorption and the external environmental conditions are different. But it has better fixation. Fixed as much growth hormone is how much, the concentration is constant, the original concentration of suitable for growth is transferred to the agar, and finally back to the plant, so there is no effect, but this is only limited to the same species of plants.