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PLANTS (pgs. 551-572) KINGDOM PLANTAE • • • • • • • Multicellular Eukaryotic Cell walls of cellulose Carry out photosynthesis using chlorophyll Trees, shrubs, grasses, mosses, ferns Most are autotrophs Some are parasites or saprobes that live on decaying material What do plants need to survive? -sunlight -water -minerals -gas exchange (need oxygen and carbon dioxide) Early Plants • The first plants evolved from an organism much like the multicellular green algae living today. These organisms in water provided oxygen in the atmosphere. • The first land plants to evolve were the mosses, then the ferns, then the cone-bearing plants and finally the flowering plants. Plants had to overcome 3 obstacles to be terrestrial Desiccation- prevent losing water. This is accomplished by the waxy covering over the plant called the cuticle. Transport- in water, material could diffuse across the membrane; on land this doesn't work. Vascular tissues (xylem and phloem) run the length of the plant and transport necessary nutrients. Reproduction- in water the sperm could swim to the egg, on land this is not possible. Now their sperm (pollen) is air born. PLANTS • Botanists study plants • Plants are divided into 4 groups based on three features: 1. water-conducting tissues 2. Seeds 3. flowers • 90% of plants on earth are flowering plants BRYOPHYTES • • • • • • • • • Nonvascular plants called mosses, liverworts, hornworts Do not have true roots, stems or leaves Depend on water for reproduction Small and must live in wet places Examples: Sphagnum and peat moss Phyla: 1. Phylum Bryophyta-mosses that grow in extreme environments in areas with water. They produce a thin stalk, each containing a capsule called the sporophyte. They have rhizoids instead of roots. 2. Phylum Hepaticophytaliverworts. They resemble the shape of a liver. they have flat leaves and produce gametes in sporophytes that look like little green umbrellas. 3. Phylum Anthocerophytahornworts. Produce gametes in sporophytes that look like a green horn. Page 557....Draw and Label the picture of Moss Sporophyte Mosses, Liverwort, Hornwort Seedless Vascular Plants (tracheophytes) • Vascular tissue is specialized to conduct water and nutrients throughout the plant • They are key cells in xylem, a transport subsystem that carries water upward from the roots. • Vascular plants also have phloem, which transports solutions of nutrients and products of photosynthesis. Seedless Plants • Seedless vascular plants • • • • • include club mosses, horsetails, and ferns. They have true roots, stems and leaves Roots are underground organs that absorb water and nutrients or minerals Leaves are photosynthetic organs that contain bundles of vascular tissue that is gathered into veins made of xylem and phloem Stems are supporting structures that connect roots and leaves and transport water and nutrients between them Ferns have underground stems called rhizomes and large leaves called fronds CLUB MOSSES HORSETAILS SEED PLANTS • Seed plants became the most dominant group of photosynthetic organisms on land Two groups: • Gymnosperms • Angiosperms Gymnosperms • Gymnosperms bear their seeds directly on the surfaces of cones. • Conifers • Page 565....draw seed structure and label it ANGIOSPERMS • Angiosperms, also known as flowering plants, bear their seeds within a layer of tissue that protects the seed. • They develop unique reproductive organs known as flowers that attract pollinators. • Flowers contain ovaries which surround and protect the seeds. • Angiosperm means "enclosed seed". • After pollination the ovary develops into a fruit, which protects the seed and aids in dispersal when animals eat it. Parts of a flower Seeds • A seed is an embryo of a plant that is encased in a protective covering called a seed coat and surrounded by a food supply. • An embryo is an organism in its early stage of development. Flowering Plants: Monocots vs. Dicots Flowering plants can also be subdivided into: 1. Woody Plants: made of thick cell walls that support the plant and include plants such as trees, shrubs and vines 2. Herbaceous Plants: that do not produce wood as they grow and include plants such as dandelions, petunia, and other flowers Angiosperms can also be organized based on plant life spans • Annuals: grow only one season • 2. Biennials: grow for two seasons • • 3. Perennials: live for more than two years Chapter 23 – Special Tissue in Plants • Roots: absorb water and nutrients, anchors plants in the ground, hold soil in place to prevent erosion • Stems: are a support system for the plant, a transport system carrying nutrients, a defense system that protects the plant against predators and disease • Leaves: are the plant's main photosynthetic systems. The broad, flat surfaces of many leaves increase the amount of sunlight plants absorb. Pores in the leaves help prevent water loss and let oxygen out and carbon dioxide in. Main Plant Tissues Plants consist of three main tissue systems: • Dermal • Vascular • Ground tissues Dermal: The outer covering of a plant. A single layer of epidermal cells that are covered in a thick waxy coating called the cuticle. On the underside of leaves, dermal tissue contains guard cells that regulate water loss and gas exchange Vascular Tissue • Vascular forms a transport system that moves water and nutrients. • Xylem transport water upward from the roots. • Phloem transports nutrients and products of photosynthesis throughout the plant. Ground Tissue • Cells that lie between dermal and vascular tissues Meristems • Clusters of tissues that make the plant grow continuously throughout its lifetime. • Apical meristem: located near the end, or tip, of each growing stem and root. They let them increase in length. It is the only plant tissue that produces new cells by mitosis. Roots • The two main types of roots are: – Taproots – which are found in dicots • They are long and reach deep into the ground, or short like a carrot that stores sugars and starches – Fibrous – which are found in monocots • Branch out to help prevent erosion Roots • A mature root has an outside layer, the epidermis, and a central cylinder of vascular tissue. Between these two tissues lies a large area of ground tissue. • The surface of the root has cellular projections called root hairs that penetrate the spaces between soil particles and produce large surface area. • Roots grow in length as their apical meristem produces new cells near the root tip. These fragile cells are covered by a tough root cap that protects the root as it forces its way through the soil. It secretes a slippery substance that lubricates it as it grows. • Water moves into the vascular cylinder by osmosis • The reason water and minerals only move upward through the system is because it needs to generate enough pressure to move water out of the soil and up into the body of the plant. • Root pressure produced within the cylinder by active transport, forces water through vascular cylinder and into the xylem. Stems • Stems have three functions: – They produce leaves, branches and flowers – They hold leaves up to the sunlight – They transport substances between roots and leaves Vascular Tissues in Stems • In monocots, vascular bundles are scattered throughout the stem. • In dicots and most gymnosperms, vascular bundles are arranged in a ring. Primary Plant Body – Stem Anatomy • Young dicot stems have vascular bundles usually arranged in a ringlike pattern. The cells inside the ring are known as pith, while those outside form the cortex of the stem. Primary and Secondary Growth • Plants grow by producing new cells at the tips of roots and shoots. The method of growth is called primary growth, and it means the plant is growing in length. • The plant also grows in width. This is called secondary growth. In conifers and dicots, secondary growth takes place in lateral meristematic tissues called the vascular cambium (produces vascular tissues and increases thickness of stems) and cork cambium (produces the outer covering of stems). Bark • Bark includes all of the tissue outside the vascular cambium. The cork cambium. • The cork cambium surrounds the cortex and produces a thick protective layer of cork which have thick walls made of fats, oils, waxes and are waterproof. • The outermost cork cells are usually dead. As the stem increases in size, the dead bark often cracks and flakes off. Leaves • To collect sunlight, most leaves have thin, flattened sections called blades which are attached to a stem by a thin stalk called a petiole. Leaves • They have pore like openings on the underside called stomata, which allow for gas exchange. Each stoma consists of two guard cells which control the opening and closing of the stomata by responding to changes in water pressure. Transpiration • Transpiration is the loss of water through leaves. The lost water is replaced by water drawn into the leaf through xylem vessels in the vascular tissue. Transport in plants • The combination of root pressure, capillary action and transpiration provides enough force to move water through the xylem tissue of even the tallest plant. • Water molecules are attracted to each other by cohesion and to other substances by adhesion. The movement of water upward against gravity because of these two properties is called Capillary Action or Transpiration Pull. • For trees and other tall plants, the combination of root pressure and capillary action does not provide enough force to lift water to the top of the tree. • The major force in water transport is provided by the evaporation of water from leaves during transpiration. When water is lost through this process, osmotic pressure moves water out of the vascular tissue of the leaf. • The movement of water out of the leaf pulls water through the vascular system all the way from the roots. This is called transpiration pull. On a hot day, a small tree may lose as much as 100 liters of water to transpiration. The stomata and guard cells control water loss. Osmotic Pressure • Osmotic pressure keeps a plant’s leaves and stems ridgid, or stiff. High transpiration rates can lead to writing from loss of water. • Plants pump sugars into their fruits. This movement takes place in the phloem. In cold climaters, plants pump food down to the roots for storage. Phloem carries out this seasonal movement of sugars within a plant. Phloem is able to move nutrients in either direction to meet the nutritional needs of the plant.