Plant Tissues and Organs

1. Plant Tissues and Organs

2. Plant Tissues • All plants are made up roots, stems, leaves and flowers. These structures are made up of cells • These cells are not always the same in structure. They differ depending on what function they perform • Some groups of cells have a supportive function. Others may be involved in photosynthesis. • Cells which have a similar function, are similar in structure and form tissues.

3. Examples of some Plant Tissues • Epidermal tissue – a single layer of cells found covering the surface of the plant • Some epidermal cells are specialised for perform a certain function. Examples: • Guard cells in leaves • Roots hairs in roots

4. Xylem – transports water from the roots via the stems to the leaves. The cells are elongated and hollow with thickened, lignified cell walls. They are arranged end-to-end. They also have a supportive function. Vascular Tissue: Two types:-

5. Vascular Tissue: Phloem – transports food made in the leaves to the rest of the plant. Cells are also elongated and arranged end-to-end.

6. Supportive Tissues Supportive tissues – collenchyma and sclerenchyma

7. Other Plant Tissues • Photosynthetic Tissue – found in the leaves – the cells contain many chloroplasts. • Storage and packing tissues called parenchyma. This tissue is the most common plant tissue found in plants.

8. Plant Organs Tissues are grouped together to form a structure with a special function. This structure is called an organ. Examples of plant organs are: • Roots • Stems • Leaves • Flowers

9. Function of the Root • To anchor the plant in the soil • To absorb water and nutrients from the soil for photosynthesis in the leaves • Some roots store extra food – e.g. carrot

10. Function of the Stem • Support the plant • Conduct water and nutrients from the roots to the leaves • Conduct food (glucose) manufactured in the leaves to rest of plant

11. Structure and Functions of a Plant Leaf

13. Function of the Leaf • Photosynthesis • Gaseous exchange • take in O2 and release CO2 during respiration • take in CO2 and release O2 during photosynthesis Water Vapour can be lost from the surface of the leaf in a process known as Transpiration.

14. Photosynthesis Glucose (Stored as starch) Energy (Sun) + O2 (Released into air) + CO2 (from air) + H20 (from roots) In chloroplast (chlorophyll)

15. Structure of the Leaf Transverse section of a leaf

16. phloem xylem Water-carrying cell Opening for CO2 and O2 and water vapour Leaf vein Transverse section of a leaf at cellular level

20. Stomata: Functions • The stomata are responsible for the interchange of gases for respiration and photosynthesis. • The stomata allow for the loss of excess water in the form of water vapour, which also allows for cooling.

21. Quiz: Label the parts of the leaf Stoma Palisade mesophyll Spongy mesophyll cuticle Upper epidermis Air spaces A B C D E F

22. Brainstorm How are leaves adapted to their functions of photosynthesis and gaseous exchange? - Try to think of 7 adaptations

23. How is the Leaf adapted to its function? • Broad, flat-shape – large surface area for absorption of sunlight and carbon dioxide • Thin– gases have a short distance to travel (Epidermis – 1 cell layer thick) • Large air spaces between the cells of the spongy mesophyll – allow for easy passage of carbon dioxide and oxygen • Waxy Cuticle (reduces water loss) • Many stomata in the lower surface allow for the exchange of carbon dioxide and oxygen with the air outside (open during day, close at night) • More chloroplasts in upper palisade than spongy mesophyll cells where they receive the most sunlight • Branching network of veins which provide a good water supply to the cells for photosynthesis.