Transcript Plants
PLANTS Plant Characteristics • Multicellular • Autotrophic (photosynthesis) • Chlorophylls a and b in thylakoid membranes • Surrounded by cell walls containing cellulose (polysaccharide) • Store reserve food as amylose (starch) 2 Plants Classifying Plants: 2 Main Groups of Plants: A. Nonvascular: have no vessels, no roots, no stems or leaves. Examples: Mosses & Liverworts Bryophytes • Depend on water for reproduction • Lack vascular tissue (specialized tissues that conduct water and nutrients) • Can only draw up water by osmosis • Can only grow a few cm above ground Groups of Bryophytes • Mosses • Liverworts • Hornworts Mosses • Phylum Bryophyta • Grow in areas w/ water Moss Liverworts • Phylum Hepaticophyta • Produce structures that look like tiny green umbrellas that produce egg & sperm • B. Vascular: have vessels to transport food and water. They have roots, stems and leaves. Example: Grass, corn, trees, flowers, bushes • Two Types of tissue: • 1. Xylem: transports water 2. Phloem: transports food & nutrients Two Groups of Vascular Plants A. Gymnosperms • "naked seeds" • cone bearing plants (seeds grow on cones) • needle like leaves • usually stay green year round • wind pollinated • Examples: pine trees & evergreens B. Angiosperms • flowering plants • seeds are enclosed in a fruit • most are pollinated by birds & bees • have finite growing seasons • Examples: grasses, tulips, oaks, dandelions • Divided into two main groups: Monocots & Dicots Angiosperms Two Groups of Angiosperms A. Monocots • Angiosperms have have 1 seed leaf (cotyledon) • parallel veins on leaves • 3 part symmetry for flowers • fibrous roots • Example: lilies, onions, corn, grasses, wheat • • A: vascular bundle (scattered thru stem) B: ground tissue: storage, support B. Dicots • Angiosperms that have 2 seed leaves (cotyledons) • net veins on leaves • flowers have 4-5 parts • taproots • Examples: trees and ornamental flowers • • A: epidermis B: vascular bundle (arranged in a ring) C. ground tissue (pith) D. cortex Parts of the Plant A. Roots • water and minerals are absorbed (taproots vs fibrous roots) • also used to anchor the plant • movement of water up to leaves is influenced by TRANSPIRATION • Two types of roots: – Taproot-1 primary root long and thick while secondary roots are small – Fibrous Root-no single root grows larger than the rest B. Stems • Support plant • transport water through xylem • transport nutrients through phloem • a celery stalk soaked in food coloring will absorb the food coloring, you can see the xylem • Two types of stems: herbacious and woody C. Leaves • Photosynthetic organ of the plant, used to convert sunlight into food • Structures: Cuticle: waxy covering, prevents water loss Xylem: vascular tissue, transports water Phloem: vascular tissue, transports nutrients (phood) Stomata (stoma): pores used for gas exchange Guard cells: open and close stomata Mesophyll: middle tissue, cells have chloroplasts used for photosynthesis, mesophyll consists of the spongy and palisade layers Epidermis: layer of cells just under the cuticle Vein: a structure composed of xylem and phloem, veins run from the tips of the roots to the edges of leaves D. Flower • Reproductive organ of the plant • Flowers are usually both male and female • The male part of the flower is the STAMEN • The female part of the flower is the PISTIL • See your coloring sheet for more detail on flower anatomy Plant Reproduction • Pollen is produced by the stamen. • Pollen moves away from the plant via the wind or other pollinators (birds & bees) • The pollen lands on the pistil of another plant and fertilizes the eggs within the ovary • The flower petals fall off, the ovary develops into a FRUIT that encloses the seeds • Fruits are dispersed in a variety of ways (wind, animals) • Fruits are not always edible, anything with a seed inside can be considered a fruit (helicopters, acorns, dandelions) Plant Reproduction • Alternation of generations life cycle • Diploid (2n) sporophyte stage • Haploid (1n) gametophyte stage • Produce multicellular embryo protected inside multicellular haploid (gametophyte egg sac) tissue Plant Reproduction • Diploid (2n) sporophyte stage produces haploid spores by meiosis • Haploid spores undergo mitosis to produce gametophyte stage • Gametophyte makes gametes (eggs and sperm) by meiosis • Zygote (2n) produces the new sporophyte Alternation of Generations Gametophyte 2n Sporophyte 2n gametophyte 1n pollen 2n seed with plant embryo Sporophyte Ovary with 1n ovules (eggs) Asexual Reproduction in Plants • Many plants can clone themselves, a process called VEGETATIVE PROPAGATION • strawberry plants and other vine like plants send out runners, which grow into new plants • some plant clippings will grow into new plants • a Potato will grow into a new plant How Plants Grow • Germination occurs when a seed sprouts (usually caused by changes of temperature and moisture) • Monocots have 1 seed leaf (cotyledon), Dicots have 2 seed leaves • Perennials - live severval years, and reproduce many times, woody plants are perennials • Annuals - a plant that completes its life cycle in one growing season (grows, flowers, reproduces and then dies) • Biennials - takes two growing seasons to complete, it reproduces in the second growing season • Plants grow only at their tips in regions called MERISTEMS • PRIMARY GROWTH makes a plant taller at roots and stems • SECONDARY GROWTH makes a plant wider, or adds woody tissue • Tree Rings tell the age of a tree, each ring represents a growing season. The photo shows a tree who has been through four growing seasons. The lighter thinner rings are winter periods. • VASCULAR CAMBIUM: area of the tree that makes more xylem and phloem and forms the annual rings Plant Hormones • Chemical substances that control a plant’s pattern of growth and development and the plant’s response to environmental conditions • Auxins-simulate cell elongation • Cytokinins-simulate cell division • Gibberellins-increase in size • Ethylene-causes fruits to ripen Response to Stimuli • Phototrophism-Response to light • Gravitrophism-Response to gravity • Thigmotropism-Response to touch