Texas FFA Nursery Landscape Practice Exam

What does the term "callus" refer to in horticulture?

1. The tissue on the collar of a limb

2. A disease of plant leaves and limbs

3. The first tissue to develop on a cutting just before the roots form

4. Deformed growth on plant limbs

The correct answer is: The first tissue to develop on a cutting just before the roots form

In horticulture, the term "callus" specifically refers to the tissue that forms at the site of a cutting just before roots begin to develop. This process is crucial in plant propagation, particularly in asexual methods such as cuttings. When a plant cutting is made, the damaged tissue at the cut site responds by producing callus tissue, which is essentially a protective layer that helps to seal the wound and prevent desiccation. The development of callus is a key precursor to root formation, as it creates the conditions necessary for the cutting to establish roots and grow into a new plant. This understanding of callus formation is vital for successful propagation techniques. If callus does not form properly, the cutting may fail to root, leading to a lack of new plant growth. The other options presented, while relating to plant anatomy and diseases, do not accurately capture the definition or role of callus in the context of horticulture.