This jade plant has been grown with enough light and the right amount of water. How could you manipulate the plant into producing hormones to grow a more bushy plant?

By removing the apices of the plant

Explanation:

A plant can be manipulated into becoming more bushy by removing the apices of its shoots.

A plant hormone called auxin which promotes cell elongation and plays a huge role in the maintenance of apical dominance is usually produced at the tips (apices) of stems. When the tips are removed, auxin production is disrupted, and lateral buds that have been initially suppressed by the auxin production begin to flourish, leading to the plant becoming more bushy.

Hence, to trick the jade plant to become more bushy, just remove apices of the shoots the plant.

the answer is:

carbon dioxide