Transcript seed cone
Plant Anatomy Undifferentiated plant tissue which gives rise to new cells (growth). This can differentiate into any other type of tissue needed by the plant. at tips of branches & roots: – primary growth= increased height – apical meristem around the perimeter of roots & stems: – Secondary growth= increased diameter – lateral meristem – In stems in can produce wood, cork(bark) also occurs in roots. VASCULAR TISSUE = TRANSPORT: • Vascular tissue consists of xylem and phloem. These two types of vessels run side-by-side, extending from roots to leaves. They provide channels for the transport of water and nutrients. Xylem- Conducts water and minerals from the roots to the leaves. • Composed of ground cells and 2 types of conducting cells: – Tracheids (A) • thin cells w/ slanted ends-stacked atop each other. Pits allow transfer between cells – Vessel elements (B) • Perforated end walls. Vessel members join together into long tubes called vessels. Occur primarily in angiosperms A B Phloem • Carries dissolved “stuff” synthesized by the plant • Phloem composed of 2 types of cells – sieve –tube elements (A) • Possess no nucleus, mitochondrion, or chloroplast B • Rate of flow of substances through sieve-tube elements is high. – Companion cells (B) • Adjacent companion cells – These cells perform enough biochemistry to keep the sieve-tube elements and themselves alive. A Transport of food. The xylem sap is always a very dilute solution, but the phloem sap may contain up to 25% of dissolved solids such as sucrose and amino acids. Plant Organs: •Roots •Stems •Leaves Root Functions: • Absorb Nutrients • Anchor the Plant • Store Food Roots Control Water Flow: • Beneath the root epidermis is a ring of waterproof cells called the Casparian Strip. • The Casparian strip forces water to move THROUGH the cytoplasm to the vascular tissue. Pathway of water and Minerals through the roots toward the xylem • This controls absorption of water and nutrients toward the xylem. Water can NOT enter from outside the cells after the Casparian strip. Root Pressure: • High mineral concentration inside vascular tissue attracts water via osmosis. • This pressure from water entering root pushes fluids up the xylem against gravity as a result of root pressure. • This pressure moves water away from the roots allowing more water to enter the root tips. Monocot Dicot Types of Roots: Lateral Roots • TaprootsCommon in dicots • Lateral Roots- Extensions off the taproot • Fibrous roots – Common in monocots Taproot STEMS: Stems have four main functions : 1) Support and t elevation of leaves, flowers and fruits. 2) The stems keep the leaves in the light and provide a place for the plant to keep its flowers and fruits. 3) Transport of fluids between the roots and the shoots in the xylem and phloem. Storage of nutrients. 4) The production of new living tissue. Stems have cells called meristems that annually generate new living tissue. STEMS – • Vascular bundles run its length – Monocots: scattered throughout – Dicots: arranged in a ring around the edge LEAVES: Organized to maximize sugar production. Waxy cuticle cover minimizes water loss Leaf mesophyll contains the palisade mesophyll, important for photosynthesis and spongy mesophyll, for diffusion of gasses into and out of the leaf. Veins contain vascular bundles for carrying water and nutrients from soil to the leaves and products of photosynthesis away from the leaves to other parts of the plant. Stomata regulate water loss and gas exchange MONOCOT LEAF CROSS SECTION DICOT LEAF CROSS SECTION Transpiration aids the plant in pulling water from the soil into the roots and through the rest of the plant. ( Cohesion and 4 factors which control rate of transpiration are : 1)light intensity, 2)humidity, 3)air movement, 4) temperature. ASEXUAL REPRODUCTION: • Plants can be “cloned”. • Cuttings, grafts, and runners allow for a plant to reproduce new, genetically identical individuals. SEXUAL REPRODUCTION in GYMNOSPERMS: Gymnosperms do not produce flowers. Seeds are produced inside cones. Gymnosperm produce two types of cones. The male cone is called the pollen cone. The larger female cone is the seed cone. A single tree usually produces both pollen and seed cones. Female Pine Cone Male Pine Cone • Pollination – Pollen grain lands on stigma – Pollen tube grows toward ovary – Two sperm nuclei travel down pollen tube – One sperm fertilizes the egg, second sperm fertilizes the 2 polar bodies and becomes the 3n endosperm & becomes the Polar nuclei Seed Development • After fertilization – Ovule becomes the seed. – Ovary becomes the fruit • Seed consists of: – Seed coat – Embryo – Cotyledon ( food for embryo) • Seeds packaged into an attractive box called FRUIT. • Various styles of fruit provide different types of dispersal : – Fruit eaten by animal, seed just discarded. – Fruit digested by animals, seeds released in feces. – Burred seeds carried on fur. – Winged fruits -wind dispersed. Seeds Differ Between Monocots and Dicots: Growth of a Plant Toward or Away From a Stimulus. • Phototrophism – growth influenced by light. ( Positive – toward; negative – away) • Gravitropism-growth influenced by gravity. ( Positive – toward; negative – away) • Thigmotropism- growth influenced by contact with the plant. ( Positive – toward; negative – away) • Caused by the unequal accumulations of Auxin. • Auxin accumulates on the dark side of a plant. • Cells containing auxin will elongate faster. • Faster growth on the dark side causes plant to tilt toward the light. A key regulatory process in plants to insure that roots grow down and shoots grow up in developing seedlings The result of the hormones Auxin and Gibberellin. Touched cells produce Auxins and transport it to untouched cells. Some untouched cells will then elongate faster so growth Bends around the object. Plants respond to length of day to control many activities. Among these is the flowering of the species. This ability to is linked to an inner light sensitive circadian rhythm.