OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

How do plant hormones from agar jelly enter the plant?

1. Evaporation

2. Diffusion

3. Osmosis

4. Active transport

The correct answer is: Diffusion

Plant hormones from agar jelly enter the plant primarily through the process of diffusion. Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration. In this case, when agar jelly containing plant hormones comes into contact with plant tissue, the hormones move through the plant cell membranes into the cells where they are needed, as they naturally spread from areas of higher concentration in the agar to lower concentration within the plant cells. This process is passive and does not require energy, which distinguishes it from active transport, which involves the movement of substances against their concentration gradient with the use of energy. Osmosis, while a critical process in plants for water movement, specifically refers to the diffusion of water across a semi-permeable membrane, rather than the movement of hormones. Evaporation is unrelated to the uptake of substances into plants, as it involves the transition of water from liquid to vapor, not the uptake of hormones. Thus, diffusion accurately describes how the plant hormones from agar jelly enter the plant.