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The Structure of Flowering Plants 1 Contents External Structure The Root System - Functions The Shoot System - Buds - Leaves - Flowers Growth and Tissues in plants Organisation of plant tissues Types of tissues Vascular Tissues in Angiosperms Xylem Phloem Sieve tube cells Companion cells Monocot & Dicot plants 2 External Structure 3 The Root System 4 Roots Usually white in colour – why? Tip protected by root cap Root hairs – absorb water and minerals 5 Functions of the root 1. To anchor the plant in the ground 2. To absorb water and minerals from the soil 3. Sometimes to store food 6 The Shoot System Consists of an upright stem bearing Buds Leaves Flowers 7 Functions of the stem 1. 2. 3. 4. Transport water and minerals from the roots to all parts of the plant Transport food from the leaves to all parts of the plant Support the leaves and hold them up to the sun for light Sometimes to store food 8 Buds (1/2) A bud is an undeveloped shoot Apical buds – at tip of stem where growth takes place Lateral buds – in axil of leaf – produce side shoots and branches 9 Buds (2/2) Axil = angle between the petiole of a leaf and the stem Node = point on a stem where a leaf or leaves are attached Internode = the part of a stem between two nodes 10 Leaves Lamina = flattened leaf blade Veination of leaf – two types 1. Netted e.g. 2. Parallel e.g. Attachment to stem – two ways 1. Petiole e.g. 2. Sessile e.g. 11 Functions of the leaf 1. To make food by photosynthesis 2. To allow exchange of gases – explain 3. To allow transpiration – explain 4. Sometimes to store food e.g. 12 Flowers Formed from flower buds May occur singly or as an inflorescence Four main parts Sepals Petals Stamens Carpels 13 Typical flower structure 14 Function of the Flower 1. Reproduction 15 Growth and Tissues in plants meristem: tip of shoots and roots of plants. Area of active cell division (mitosis) which produces ‘simple’ cells which later undergo elongation and differentiation to give rise to the various plant tissues e.g. xylem, phloem, etc. Apical meristems are found at tip of shoots and roots 16 Organisation of plant tissues 17 Types of tissues When meristems divide they produce three types of tissue 1. Dermal – epidermis = outer covering 2. Ground – inside of plant e.g. cortex and pith of stem mesophyll of leaf 3. Vascular – transport tissue = xylem & phloem 18 Tissue types in L.S. of root 19 Tissue types in T.S. of root 20 Tissue types in L.S. of stem 21 Tissue types in T.S. of stem 22 Tissue types in T.S. (V.S.) of leaf 23 Vascular Tissues in Angiosperms Two types Xylem – provides support and – transports water and minerals Phloem – transports food 24 Xylem Two kinds of conducting cell – xylem tracheids and – xylem vessels On maturity both are dead, hollow and contain no cytoplasm 25 Xylem tissue 26 Xylem tracheids Long cells tapered at both ends Pits in the walls – allow water and minerals to move sideways from cell to cell Walls thickened with lignin for support 27 Xylem vessels Elongated cells with spiral bands of lignin No end walls – form a continuous tube Wider than tracheids 28 Phloem Consists of – phloem sieve tube cells and – companion cells 29 T.S. of phloem tissue 30 L.S. of phloem tissue 31 Sieve tube cells Long cylindrical cells stacked end to end End walls = sieve plates – have holes Allow cytoplasm to move from cell to cell Mature cells have no nucleus 32 Companion cells Found beside sieve tube cells Has cytoplasmic connections with sieve tube cell Has a nucleus which controls activities of both companion and sieve tube cell 33 Identification of Monocot & Dicot plants Monocotyledons Number of cotyledons One Arrangement of Scattered in the stem vascular bundles in the stem Dicotyledons Two In a distinct ring pattern Leaf venation Parallel Netted Number of flower parts In threes In fours and fives Woody or herbaceous Almost all are May be woody or herbaceous, there are herbaceous very few woody monocotyledons 34 The differences between monocots and dicots 35 END 36