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Chapter 27

chapter 27 and chapter 28 bio 1225 notes.docx

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Western University
Biology 1225
Michael Butler

Chapter 27 Organization of the Plant Body and Chapter 28 Plant reproduction A plant has 2 organ systems : Roots and Shoots a. Roots - mostly below ground - absorb water and dissolved minerals - serve to anchor plant b. Shoots - mostly above ground - includes 1. Stems – structural support 2. Leaves – photosynthetic production of sugars from sunlight 3. Flowers – reproductive organs Roots, Shoots (stems, leaves, flowers) consist of simple and complex tissues 1. Simple Tissues – consist primarily of one type of cell a. Parenchyma – parenchyma cells – ***photosynthesis, storage, tissue repair, secretion b. Collenchyma – Collenchyma cells – pliable structural support – ***stringy support strands in celery are collenchyma c. Sclerenchyma – Fibres of Sclereids – structural support 1 2. Complex tissues – consist of many cell types a. Dermal tissue – cover and protects the plants body i. epidermis – outermost tissue of young plants ii. periderm – replaces epidermis and forms on older plants b. Vascular tissues – ***tissues that distribute water and nutrients throughout the body i. ***xylem a. transports dissolved minerals and water upwards from the roots b. consists of trecheids and vessel cells/membranes c. the walls are pitted d. ***dead at maturity e. ***Most of a mature tree is composed of xylem ii. phloem – a. complex vascular tissue of plants distributes sugars through its sieve tubes b. ***alive at maturity c. Ground tissue - makes up the bulk of the plant – everything other than dermal and vascular tissue Monocots and Eudicots have the same tissues organized in different ways: Monocots include - lilies, orchids, grasses and palms - have one cotyledon (***seed leaf of embryo) - flower is in multiple of 3 - leaf veins usually parallel with one another - pollen grain has 1 pore Eudicots include - flowering shrubs and trees, vines, tomatoes and dandelions - have two cotyledons (seed leaves of embryo) - flower is in multiples of 4 or 5 2 - leave vein in netlike array - pollen grain has 3 pores Stems Roots and Leaves Stem (Shoot) - form the basic structural framework of a flowering plant, providing support for flowers and keeping leaves positioned for photosynthesis - In many plants they function in storage and reproduction - New shoots develop at nodes (region of a stem where leaves form - Vascular bundles extending through stems conduct water and nutrients between different parts of the plant a. Eudicots – vascular bundles of eudicots stems form a cylinder that divides the ground tissue into cortex and pith b. Monocots – vascular bundles of monocots are distributed throughout the ground tissue Roots - Take up water and minerals from the soil and transport these substances to other parts of the plant - Inside each root is a vascular cylinder with long strands of xylem and phloem - Monocots have a fibrous root system and Eudicots have a taproot system - Root hairs increase a root’s surface area for absorbing water and minerals from soil. - Ions move into a root by osmosis 3 Leaves - Most leaves are thin, with a high surface to volume ratio - They are the main site of photosynthesis - Leaves, which form at nodes on stems have photosynthetic mesophyll and veins (vascular bundles) between upper and lower epidermis. - Most stomata occur in the lower epidermis (to balance water retention with gas exchange) - Thick water proof ***cuticle layer on the top for retention of water - Substances absorbed by a root go to the vascular cylinder to be distributed to the rest of the plant - Components include a. mesophyll (photosynthetic cells) b. veins (bundles of vascular tissue) c. epidermis (cuticle secreting) 1. Cuticle a. resists water loss b. forms surface of epidermal cells c. contains waxes and cutins d. resistant to microbial attack 2. Stomata a. on underside of leaf on epidermis b. balances water retention with gas exchange 4 Plant growth 1. MERISTEMS – all plant tissues originate at divide. 2. ***Active Mitosis occurs at the meristem 3. Primary growth (lengthening) arises at ***apical meristems*** in the tips of young shoots and roots. Fluid Movement in the Plant Body 1. At least 90% of water transported from roots to leaves is lost by evaporation- Only 2% is used in metabolism which is important for photosynthesis, growth, and membrane function 2. A cuticle and Stoma (stomata pl.) help the plant conserve that water 3. ***Cuticle is impermeable to wa
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