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07 plant cells, tissues and organs

This document discusses plant cells, tissues, and organs. It describes how plant cells can be specialized into tissues for specific functions. The major plant organs are then examined in more detail: leaves contain tissues like palisade and mesophyll for photosynthesis; stems provide structure and transport through vascular bundles; roots absorb water and minerals through root hairs and vascular tissue; and flowers facilitate reproduction through pollination and seed production. The roles of meristem, buds, and plant hormones in growth and repair are also outlined.

Science◦
PLANT CELLS, TISSUES, & ORGANS
PLANT CELLS, TISSUES, & ORGANS
SPECIALIZED CELLS & TISSUES IN PLANTS
•Tissue: group of specialized cells •Organ: Group of several types of tissues working towards a specific function •Meristem: unspecialized cell that can form specialized cells in plants SPECIALIZED CELLS & TISSUES IN PLANTS
Plant organs: •Leaf •Stem •Root •Flower PLANT ORGANS
Leaf: •Dermal tissue •Palisade tissue •Mesophyll tissue •Vascular bundles PLANT ORGANS: LEAF
Leaf tissues: • Dermal tissue • Waxy cuticle – limits water loss • Protects the leaf • Palisade tissue • Prime site of photosynthesis – palisade cells and chloroplast • Mesophyll tissue • Loosely packed cells • Spaces contain gases such as H2O, CO2 and O2 • Vascular tissue • Xylem – transports water to the photosynthesizing cells • Phloem – transports sugar throughout the plant • Small vein branches – every cell gets water and nutrients PLANT ORGANS: LEAF
PLANT ORGANS: LEAF Leaf: Palisade tissue • Contains chloroplasts that perform photosynthesis
Leaf: Lower epidermis • Exchange of gases • Guard cells • Control opening and closing of stomata • Stomata • Connected to spongy mesophyll • CO2 enters, O2 and H2O exits through them • Transpiration – evaporation of water from leaves PLANT ORGANS: LEAF
Stem •Provides physical support and transports sap •Composed mainly of xylem tissue • Dead tubular hollow cells fortified with lignin •Vascular bundle • Phloem (living porous cells) exchanges materials with neighbouring cells PLANT ORGANS: STEM
Roots: •Anchor a plant to the ground •Allow water and minerals uptake from the soil •Some also act as plant’s storage area PLANT ORGANS: ROOTS
Fibrous root • Large surface area to absorb water • Stabilize soil • Prevent erosion & landslides Tap root • Allows plant to reach far underground for water • Anchors the plant PLANT ORGANS: ROOTS
•Dermal tissue • Root hair – increase surface area for absorption •Ground tissue • Cortex – provide support • Pericycle – vascular tissue PLANT ORGANS: ROOTS
•Reproduction - pollen and eggs •Pollination: transfer of pollen to female parts of flower •Seeds are produced and embedded in fruits •Hormone called ethylene stimulates ripening of fruits PLANT ORGANS: FLOWERS
Buds: Swelling of the stem • Terminal Bud – most active growth, produce Auxin • Lateral Bud – dormant regions, inhibited by Auxin • Auxin = class of plant growth substances (hormones) REPAIRING & REPLACING SPECIALIZED CELLS
PLANTS UNDER ATTACK