Plant Cells & Leaves 4/28/2017 Bellwork Why do we think that all organisms must have evolved from similar starting points?

Starter: CAF: How is a leaf like a solar cell? Plant Cells & Leaves 4/28/2017 Starter: CAF: How is a leaf like a solar cell? Leaves work in a similar way to the solar cell. They both need a lot of light energy to work. Photosynthesis takes place in the chloroplasts inside the leaf cells.

Structure of a leaf You have been given a blank diagram of a leaf. Label the tissues and cells within the leaf. Plants are adapted to their role. There are 5 main tissue/cells you need to know. The information is around the room. Attempt the challenge questions at each one. Support: Text books Extra challenge: What do you already know about photosynthesis? Produce a mind map of your ideas.

Palisade cells The top layer of cells in a leaf are called the palisade leaf cells. They are specially adapted  to make the most of the light conditions they receive. So they have many more chloroplasts than other plant cells to catch as much sunlight at possible for photosynthesis. Palisade cells are also more block shaped so that many of them can be packed into the top layer of the leaf. Extra challenge: Why are palisade cells tall and thin (vertical), rather than horizontal? Why do root hair cells not have chloroplasts?

Spongy mesophyll Spongy mesophyll cells are not packed tightly together, which allows carbon dioxide to reach the palisade cells for photosynthesis. This tissue contains irregularly shaped cells with few chloroplasts. Extra challenge: On your diagram draw two arrows showing the movement of oxygen and carbon dioxide? (Hint: What goes into the leaf and what comes out?) Why is there fewer chloroplasts than palisade cells?

Guard cell and stomata Carbon dioxide and oxygen can’t just diffuse into the leaf. They have to be let in through special doors called stomata. Stomata are usually concentrated on the bottom of the leaf to limit water loss. Guard cells are cells surrounding each stoma, they open and close the stomata.

Waxy cuticle The outer surface of the leaf has a thin waxy covering called the waxy cuticle, this prevents water loss within the leaf by evaporation . (Plants that live entirely in water do not have a waxy cuticle). Extra challenge: Why is the waxy cuticle found on the top of the leaf and not at the bottom? (Think about what increases evaporation?) Why do plants that live in water not need a waxy cuticle? How do you think the waxy cuticle for a plant found in the desert would differ to that found in the UK?

Xylem and phloem Extra challenge: Plants need a transport system to move food, water and minerals around. They use two different systems – xylem moves water and solutes from the roots to the leaves and  phloem moves food substances from leaves to the rest of the plant. Xylem vessels are involved in the movement of water through a plant from its roots to its leaves. Water: Is absorbed from the soil through root hair cells Is transported through the xylem vessels up the stem to the leaves Evaporates from the leaves Phloem Phloem vessels are involved in translocation. This is the movement of food substances from the stems to growing tissues and storage tissues. Extra challenge: Xylem transport water and mineral ions. What mineral ions do plants need?

Review: Questions Grade D: What is the function of the mesophyll tissue? (2 marks) Grade C: Explain why it is important that xylem cells are hollow. (2 marks) Grade B: How is the leaf adapted for photosynthesis? (3 marks) Grade A:When do plants respire and when do they photosynthesise? Explain your answer. (3 marks)

2 quick practicals 1. Looking at stomata 2. Boiling leaves Peel the nail varnish off the back of the leaf. Place on a microscope slide. Find the stomata under the microscope Draw what you see. I put a leaf in boiling water. I saw.... I see this because the heat makes the... I saw this happen mostly from the...... of the leaf. This is because the bottom of the leaf has...

Plant deficiencies Magnesium Deficiency Yellow Leaves Nitrogen Deficiency Stunted growth

What happens to the glucose produced? carbon dioxide from the air water from soil photosynthesis oxygen glucose out of leaf through stomata some oxygen and glucose used in respiration cellulose for cell walls proteins for growth and enzymes starch for storage fats and oils for storage

Review: True or false – rewrite false as true Photosynthesis is when a plant breathes Plants use glucose in photosynthesis Leaves have a large Surface area to capture as much sunlight as possible Leaves have holes in them called tomatoes The waxy cuticle prevents water loss Oxygen is produced in photosynthesis Chlorophyll is purple Chlorophyll absorbs sunlight Photosynthesis occurs at night Chlorophyll is found in the nucleus