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Plants Chapters 22, 23, & 25 Are eukaryotic, are multicellular, and have cell walls. Adaptations of plants Meristem– where new cells are found; tip of stem. • Plants grow in response to environmental factors: – Light – Moisture – Gravity – Temperature Adaptations of plants Some plants respond to chemicals or hormones. Auxin – is a hormone that makes stems grow toward light ad away from the pull of gravity. They make roots grow away from sunlight and toward the pull of gravity. Cytokinins – hormones that stimulate cell division and make dormant seed sprouts. Opposite of auxins. Adaptations of plants Tropisms – response to gravity, light, and touch. • Gravitropism – response of a plant to gravity. Ex. Roots grow into soil. • Phototropism – response of a plant to light. Ex. Change in color; leaves fall off; grow in direction of light. • Thigmotropism – plant’s response to touch. Ex. Venus flytrap. Adaptations of plants Adaptations • Aquatic plants – live in mud with little oxygen so have air-filled sacs that oxygen diffuses out of. • Salt water plants – cells pump slat out of leaves. • Desert plants – (xerophytes) tolerate heat, sand, winds and little rain. Seeds are often dormant. • Carnivorous & Parasitic plants – soil has little nutrients so must trap & digest insects or live on a host plant to get nutrients. • Epiphytes – not rooted in soil so grow directly on other plants. (not parasites) • Many plants produce chemicals that are poisonous if eaten. Tobacco – Nicotine. Classification of Plants Plant Kingdom Non-flowering Plants Flowering Plants Plant Life Cycle • 2 phases – Sporophyte – diploid (2N) – Gametophyte – haploid (N) Alternating from diploid to haploid is called alternation of generations. • Use energy from sunlight to carry out Photosynthesis. A plant can be divided into 3 parts . 3 groups Non - flowering Plants Mosses Ferns Gymnosperms Do NOT produce flowers Examples of Mosses Spore-producing capsule spores Characteristics of Mosses (Bryophytes) .Simplest plants .No true roots, No vascular tissues (no transport) .Simple stems & leaves .Have rhizoids for anchorage; no roots .Spores from capsules (wind-dispersal) .Damp terrestrial land A leaf (finely divided into small parts) underground stem root Characteristics of Ferns .True roots, feathery leaves & underground stems .have vascular tissues (transport & support) .Spore-producing organ on the underside of leaves called a sporangia (reproduction) .Damp & shady places needle-shaped leaves Male cones (in clusters) Female cones (scattered) Characteristics of Gymnosperms .tall evergreen trees .roots, woody stems .needle-shaped leaves .vascular tissues (transport) .cones with reproductive structures .naked seeds in female cones .dry places Angiosperms – Flowering Plants • Have reproductive organs called flowers. • Flowers attract animals which carry pollen (pollination). • Seeds are protected and develops into a fruit. • 2 groups – monocot (1 seed leaf)& dicot (2 seed leaves). • Annuals (1 season), Biennials (2 seasons), Perennials (many years) . 2 groups Flowering Plants Monocotyledons Dicotyledons . roots, stems, leaves . vascular tissues (transport) . flowers, fruits (contain seeds) Monocotyledons Parallel veins Characteristics of Monocotyledons . one seed-leaf . leaves have parallel veins . herbaceous plants . e.g. grass, maize Dicotyledons Veins in network Characteristics of Dicotyledons . two seed-leaves . leaves have veins in network . e.g. trees, sunflower, rose Roots, Stems, & Leaves • Made up of: – Dermal tissue -“skin”; prevents water loss. – Vascular tissue -moves water & nutrients. – Ground Tissue – cells that lie b/w dermal & vascular. – Meristematic – responsible for new plant cells and growth. Roots, Stems, & Leaves Roots: • Seedlings grow into primary roots, then to secondary roots. • Has a vascular cylinder (xylem & phloem). • Function is to anchor plant to ground & absorb water and dissolved nutrients from the soil. • Root pressure forces water upward. Roots, Stems, & Leaves Stems: • Function is to produce leaves, branches & flowers; hold leaves upright to sun; transport water & nutrients b/w roots and leaves. • Monocot stems-vascular bundles are scattered throughout stem. • Dicot stems-vascular bundles are in a ring & contain xylem and phloem tissue. Roots, Stems, & Leaves Leaves: • Plants main organs. • Make food (photosynthesis). • Have chloroplasts. • Xylem and Phloem tissue are in bundles called veins which connect to the stem. • Stomata allow air/gases in & out. Transport in Plants • • • • Xylem – moves water. Phloem – moves sugars. Root pressure forces water up. Water is pulled up by a force called cohesion (molecules pulled together). • Water molecules are also attracted to other molecules by adhesion. • Capillary action is cohesion and adhesion together causing water to move upward. Water will move higher in a narrow tube than in a wider tube. Plant Classification Plants Non-flowering Sporebearing No roots Mosses with roots Ferns Naked seeds Gymnosperms Flowering 1 seedleaf Monocots 2 seedleaves Dicots