Anatomy of Flowering Plants

Anatomy is the study of the internal structure of organisms. In plants, cells are organised into tissues, and tissues into organs. This chapter describes meristematic tissues: apical, intercalary and lateral meristems, which keep dividing. It also describes permanent tissues, simple and complex. Simple tissues are parenchyma, collenchyma and sclerenchyma. The complex tissues are xylem, made of tracheids, vessels, xylem fibres and xylem parenchyma, and phloem, made of sieve tube elements, companion cells, phloem parenchyma and phloem fibres. You will learn how protoxylem and metaxylem are arranged differently in stems (endarch) and roots (exarch). The chapter then explains the three tissue systems: epidermal (with cuticle, stomata, trichomes and root hairs), ground, and vascular, with radial and conjoint, open and closed vascular bundles. You will compare the internal structure of dicot and monocot roots, stems and leaves. Examples include the Casparian strips of the root endodermis, the ring of open bundles in a sunflower stem, the scattered closed bundles of a maize stem, the palisade and spongy mesophyll of a dorsiventral leaf, and the bulliform cells of an isobilateral grass leaf.

Detailed Worksheet: Anatomy of Flowering Plants Section A - Definitions (10 marks) 1. What is a meristem? Distinguish between apical and intercalary meristems. (2 marks) 2. Distinguish between collenchyma and sclerenchyma. (2 marks) 3. What are Casparian strips? Where are they found? (2 marks) 4. Define endarch and exarch xylem with one example each. (2 marks) 5. What are bulliform cells? What is their function? (2 marks) Section B - Calculations and Applications (15 marks) 6. In a leaf peel, a student counted 30 stomata and 170 epidermal cells in one field of view. Calculate the stomatal index using the formula stomatal index = S / (S + E) x 100. What would a higher stomatal index on the lower surface indicate? (3 marks) 7. A field of view under a microscope has an area of 0.2 square mm and shows 50 stomata. Calculate the stomatal density per square mm. If the leaf area is 40 square cm, estimate the total number of stomata (1 square cm = 100 square mm). (3 marks) 8. A cross-section of a root shows 4 xylem and 4 phloem bundles, while another shows 12 xylem and 12 phloem bundles with a large pith. Identify each root as dicot or monocot. Name the arrangement (tetrarch or polyarch) and the type of vascular bundle. (3 marks) 9. A sieve tube element is 150 micrometres long and a vessel member 300 micrometres long. How many of each would form a 1.5 mm column? Why do vessels lack end walls while sieve tubes have sieve plates? (3 marks) 10. A transverse section of a stem shows: sclerenchymatous hypodermis, numerous scattered vascular bundles each surrounded by a sclerenchymatous bundle sheath, water-containing cavities and no distinct pith. Identify the stem and give three reasons. (3 marks) Section C - Diagrams (10 marks) 11. Draw a labelled diagram of the transverse section of a dicot root. (4 marks) 12. Draw a labelled diagram of the transverse section of a dicot leaf showing palisade and spongy mesophyll. (3 marks) 13. Draw labelled diagrams of stomata with bean-shaped and dumb-bell-shaped guard cells. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. Compare the internal structure of dicot and monocot stems. Explain how these differences relate to the possibility of secondary growth. (5 marks) 15. Explain the structure and functions of xylem and phloem. How do the phloem of angiosperms and gymnosperms differ? (5 marks) 16. You are given a transverse section of a young stem and a young root. Explain how you would identify each, using the arrangement of the vascular bundles, the position of protoxylem and the nature of the endodermis. (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Draw diagrams neatly with labels. Show the formula and steps for calculations.