Which of the following waste products in plants is excreted through the stomata and lenticles?

Analyze the question: It asks which plant waste product leaves the plant through stomata and lenticels (the small pores on leaves and woody stems).

Explain the concept: Plants excrete waste in different ways, depending on the substance:

• Gaseous wastes (carbon dioxide, oxygen, water vapour) leave by diffusion through stomata (leaves and young stems) and lenticels (woody stems and roots).
• Solid or liquid wastes such as tannins, alkaloids, resins, latex and anthocyanins are not released through pores. They are stored in vacuoles, bark, leaves, or fruits, and are removed when the leaves or bark are shed, or they are secreted as gums and resins.

Step-by-step solution:

1. Stomata and lenticels are pores for gas exchange, so only gases can pass through them.
2. Option A, carbon dioxide, is a gas. It is a waste product of respiration and diffuses out through these pores.
3. Option B, alkaloids (e.g. quinine, morphine), are stored in plant tissues, not released through pores.
4. Option C, tannins, are deposited in bark and leaves and are removed when these parts are shed.
5. Option D, anthocyanins, are pigments stored in the cell vacuoles of petals, fruits and leaves, and they are not excreted through pores.

Correct answer: A. carbon dioxide

Exam tip: Remember "Stomata and lenticels = gases". If an option is a gas (CO₂, O₂, water vapour), it is the likely answer. Alkaloids, tannins, resins and latex are stored or shed, not breathed out.