PRELIMINARY CONTEST 2024
Ejisuman SHS: 32 points
Archbishop Porter Girls’ SHS: 45 points
Wenchi Methodist SHS: 26 points
Mfantsiman Girls’ SHS: 44 points
West Africa SHS: 42 points
Zion College: 40 points
ROUND 1
PREAMBLE
Distinguish between collateral and bicollateral vascular bundles with respect to the following.
1. Number of strips of phloem.
ANSWER: Collateral: One strip of phloem located on the outer side of the xylem. Bicollateral: Two strips of phloem—one on the outer side and one on the inner side of the xylem.
2. Number of cambiums.
ANSWER: Collateral: One cambium strip located between the xylem and the phloem. Bicollateral: Two cambium strips—one between the outer phloem and the xylem, and another between the xylem and the inner phloem.
3. Being closed or open.
ANSWER: Collateral vascular bundles can be either open or closed. Open bundles have a cambium between the xylem and phloem and are found in dicot stems, allowing for secondary growth. Closed bundles lack a cambium and are found in monocot stems, meaning they cannot undergo secondary growth. Bicollateral vascular bundles are always open (they have two cambiums and are capable of secondary growth).
PRACTICE QUESTIONS
1. What is a conjoint vascular bundle?
ANSWER: A bundle in which the xylem and phloem lie together on the same radius.
2. In a collateral bundle of a dicot stem, which side of the xylem is the phloem on?
ANSWER: The outer side, with the xylem toward the pith.
3. What is a radial vascular bundle?
ANSWER: A bundle in which xylem and phloem lie on separate radii, as in roots.
4. Name a plant group with concentric vascular bundles.
ANSWER: Ferns.
5. Give an example of a plant with bicollateral bundles.
ANSWER: Cucurbita (pumpkin or cucumber).
6. How are the vascular bundles arranged in a monocot stem?
ANSWER: They are scattered.
7. How are the vascular bundles arranged in a dicot stem?
ANSWER: In a ring.
8. What is the function of the vascular cambium?
ANSWER: It produces secondary xylem and secondary phloem.
9. What is secondary growth?
ANSWER: An increase in the thickness of the stem or root by activity of the cambium.
10. What is the direction of the protoxylem in a stem?
ANSWER: Toward the pith (endarch).
11. What is the bundle sheath?
ANSWER: A layer of cells surrounding a vascular bundle.
12. Which type of bundle allows secondary growth, open or closed?
ANSWER: Open.