Plant Cell Organisation & Specialisation Noadswood Science, 2016

Plant Cell Organisation & Specialisation Wednesday, May 30, 2018 Plant Cell Organisation & Specialisation To describe how cells are specialised for their function

Precise Learning Meristem tissue in plants can differentiate into any type of plant cell, throughout the life of the plant. Students should be able to explain how the structures of plant tissues are related to their functions (observation and drawing of a transverse section of leaf). Plant tissues include: epidermal tissues palisade mesophyll spongy mesophyll xylem and phloem meristem tissue found at the growing tips of shoots and roots. The leaf is a plant organ. Knowledge limited to epidermis, palisade and spongy mesophyll, xylem and phloem, and guard cells surrounding stomata. Students should be able to explain how the structure of root hair cells, xylem and phloem are adapted to their functions. The roots, stem and leaves form a plant organ system for transport of substances around the plant. Xylem tissue transports water and mineral ions from the roots to the stems and leaves. It is composed of hollow tubes strengthened by lignin adapted for the transport of water in the transpiration stream. Phloem tissue transports dissolved sugars from the leaves to the rest of the plant for immediate use or storage. The movement of food molecules through phloem tissue is called translocation.

Plant Cell Draw a plant cell, labeling each of the key parts and identifying their function

Plant Cell Plant cells contain: - Cell membrane Cytoplasm Nucleus Mitochondria Ribosomes Cell Wall Vacuole Chloroplasts Cytoplasm Ribosomes Nucleus Chloroplast Cell wall Vacuole Cell membrane Mitochondria

Functions Part Function Nucleus Controls what happens in the cell (but it is not a ‘brain’)! Cell Membrane Controls what substances can enter and exit the cell Cytoplasm Where chemical reactions take place (jelly-like substance) Mitochondria Most of the cells energy is released here via respiration Ribosomes Protein synthesis occurs here Chloroplasts (Plants only) Where photosynthesis occurs (contain chlorophyll (which is green)) Vacuole (Plants only) Contains cell sap (a solution of sugar and salt) helping with rigidity Cell wall Made of cellulose, which gives support to the cell

The Leaf Leaves are designed for one thing – making food via photosynthesis Leaves are broad and flat to capture lots of light Veins carry water to the leaf, and food away to the rest of the plant (veins also support the leaf) Small holes called stomata in the underside of the leaf allow gases in and out

Leaf Components There are specialised parts to a leaf which help with photosynthesis

Epidermal Cells & Waxy Cuticle Cells in the epidermis make wax which covers the leaf surface (especially at the top) which limits water loss and acts as a protective barrier

Palisade Cells These cells are full of chloroplasts (containing chlorophyll) which it where photosynthesis takes place

Spongy Mesophyll This layer is full of air spaces which allows CO2 to reach chloroplasts in the palisade layer

Stomata Stomata are tiny holes which allow CO2 into the leaf (they also allow water to escape) The stomata are pores which open and close automatically controlled by guard cells When there is lots of water they become turgid so the pore opens When there is not much water they become flacid which closes the pore preventing water loss but it also stops CO2 getting in so photosynthesis stops too!

Xylem & Phloem Xylem transports water and mineral ions from the roots to the stems and leaves – it is composed of hollow tubes strengthened by lignin adapted for the transport of water in the transpiration stream Phloem transports dissolved sugars from the leaves to the rest of the plant for immediate use or storage – the movement of food molecules through phloem tissue is called translocation

Meristem Tissue Meristem tissue is found at the growing tips of shoots and roots and is able to differentiate into lots of different types of plant cell This allows the plant to grow

Photosynthesis

Practice Questions True or false – leaves are organ systems? Name the plant tissue where photosynthesis occurs What is the function of the air spaces in spongy mesophyll tissue? Where in a plant is meristem tissue found? Explain why the upper epidermis of a leaf is transparent

Answers True or false – leaves are organ systems – false Name the plant tissue where photosynthesis occurs – palisade mesophyll tissue What is the function of the air spaces in spongy mesophyll tissue – allow gases to diffuse in and out of cells Where in a plant is meristem tissue found – in the growing tips of shoots and roots Explain why the upper epidermis of a leaf is transparent – so light can pass through to the palisade layer which contains lots of chlorophyll for photosynthesis