Chapter 25 Notes

Chapter 25 Notes - Plants Gymnosperms: Conifers...

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Plants Gymnosperms: Conifers Angiosperms: flowering plants Monocots: 1 cotyledon, parallel leaf venation; 3 or multiples of 3 flower parts; scattered vascular bundle; fibrous root system Dicots: 2 cotyledons, netted leaf venation; 4s, 5s, or multiples thereof flower parts; circular vascular bundle; taproot Cotyledons: storage tissue that provides nutrition to the developing seedling Leaf venation: patter of veins in leaves Flower parts: number of petals, sepals, stamens, and other flower parts Vascular bundles: arrangement of bundles of vascular tissue (xylem and phloem) in stems Root: form of root Roots Root system: located underground; anchors plant in soil and gives support; absorbs water and mineral from soil Absorptive capacity of a root is increased by many branches and root hairs; Root hairs – projections from epidermal root-hair cells, responsible for absorption of water and minerals Root-hair cells are constantly being replaced Root hairs increase absorptive surface of a root tremendously Transplantation: must take a part of surrounding soil along with plant Roots produce hormone and stimulate growth of stems and coordinate with the plant Organization of Roots Root apical meristem is in the region protected by root cap Root cap cells have to be replaced constantly because they get ground off by rough soil particles as the root grows
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Zone of Cell Division: primary meristems continuously provide cells to the zone of elongation above by mitosis Zone of Elongation: cells lengthen as they become specialized Zone of Maturation: contains fully differentiated cells – recognizable because root hairs are borne by many epidermal cells Tissues of a Eudicot Root Epidermis: forms outer layer of root; consists only of a single layer of cells; majority of epidermal cells thin-walled and rectangular – but in zone of maturation, many epidermal cells have root hairs, project as far as 5-8 mm into soil particles Cortex: under epidermis, large, thin-walled parenchyma cells make up the cortex of the root; contain starch granules and cortex functions as food storage Endodermis: single layer of rectangular cells that forms boundary between cortex and inner vascular cylinder; fits snugly together; bordered on 4 sides by the Casparian strip – a layer of impermeable lignin and Suberin; Casparian strip prevents passage of water and mineral ions between adjacent cell walls; only access to vascular cylinder is through the endodermal cells; regulates entrance of minerals into vascular cylinder Vascular tissue: pericycle, first layer of cells within vascular cylinder, retained capacity to divide and can start development of branch or lateral roots; main portion of vascular cylinder contains xylem and phloem; xylem – star shaped in eudicots; phloem found in regions between arms of xylem Monocot Roots Same growth zones as eudicots roots, DO NOT UNDERGO SECONDARY GROWTH Organization of monocot tissues is slightly different Ground tissue of monocot’s root’s pith, is surrounded by a vascular ring composed of alternating xylem
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Chapter 25 Notes - Plants Gymnosperms: Conifers...

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