Lesson 37: Plant Structure & Function (PART 2)

1. Lesson 37: Plant Structure & Function (PART 2) Refer to chapters 23 & 24 in your textbook

2. Learning Goals: • I can label and describe the anatomy of a leaf. • I can explain how a leaf’s structure maximizes photosynthesis. • I can label and describe the anatomy of a flower. • I can differentiate between male & female parts of a flower. • I can explain how fruits are formed.

3. Anatomy of a Leaf • To collect sunlight, most leaves have a thin, flattened part • called a blade. The flat shape of a leaf blade maximizes the • amount of light it can absorb. • The blade is attached to the stem by a thin stalk called a • petiole.

4. Anatomy of a Leaf • The top and bottom surfaces of a leaf are covered by the • dermal tissue- epidermis. • The epidermis of nearly all leaves is covered by a waxy • cuticle, a waterproof barrier that protects the leaf and limits • water loss through evaporation.

5. Anatomy of a Leaf Vascular tissues xylem and phloem are gathered together into bundles called leaf veins that run from the stem throughout the leaf.

6. Anatomy of a Leaf • Beneath the upper epidermis is a layer of cells called the • mesophyll or “middle layer.” • Two Types of Mesophyll: • Palisade mesophyll, containing closely packed cells that • absorb light that enters the leaf • Spongy mesophyll, which is below the palisade, and has many • air spaces between its cells

7. Anatomy of a Leaf The air spaces in the spongy mesophyll connect with the outside world through stomata, small openings in the epidermis that allow carbon dioxide, water, and oxygen to diffuse into and out of the leaf.

8. Anatomy of a Leaf Guard cells are highly specialized cells that surround the stomata and control their opening and closing. Guard cells regulate the movement of gases into and out of leaf tissues.

9. Anatomy of a Flower Flowers are reproductive organs that are composed of four different kinds of specialized leaves: sepals, petals, stamens, and carpels.

10. Anatomy of a Flower • The outermost circle of floral parts contains the sepals. • Sepals enclose the bud before it opens, and they protect the flower while it is developing.

11. Anatomy of a Flower • Petals, which are often brightly colored, are found just inside the sepals. • The colors, number, and shapes of such petals attract insects and other pollinators to the flower.

12. Anatomy of a Flower • The stamens are the male parts of the flower. • Each stamen consists of a stalk called a filament with an • anther at its tip. • Anthers are the structures in which pollen grains, the • sperm is produced.

13. Anatomy of a Flower • The innermost floral parts are the carpels, which produce and • shelter the female eggs and, later, seeds. • Each carpel has a broad base forming an ovary, which contains • one or more ovules (eggs).

14. Anatomy of a Flower • The diameter of the carpel narrows into a stalk called the style. • At the top of the style is a sticky or feathery portion known as the • stigma, which is specialized to capture pollen. • Together the style and stigma make the pistil, the female portion • of the flower.

15. Development of Fruits • A fruit is a matured angiosperm ovary, usually • containing seeds. • (The term fruit applies to the sweet things we usually think of as fruits, such as apples and strawberries. However, foods such as peas, corn, rice, and tomatoes, which we commonly call vegetables, are also fruits.)