Chapter 30

Chapter 30 - Chapter 35 Primary vs Secondary Growth...

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Chapter 35 Primary vs Secondary Growth Lycophytes and Pterophytes were capable of secondary growth. Gymnosperms and Angiosperms are capable of secondary growth. Determinate Growth – stop growing when you reach a certain size (humans) Indeterminate Growth – growth occurs throughout life (plants) Annuals – germination to flowering to seed production to death w/in one year (cereal grains/legumes/wildflowers) Biennials – live two years (beets/carrots) Perennials – live many years (trees, shrubs, grasses) die b/c of bad environment Primary growth – apical meristems (tips of roots and in buds of shoots – length) makes most of herbaceous plants Secondary growth – lateral meristems (vascular and cork cambium – thickness) woody plants. Vascular cambium – adds 2 0 xylem and 2 0 phloem. Cork Cambium replaces epidermis with periderm (tougher and thicker) Primary Growth of Roots Apical Meristem – Top section – Produces 3 primary meristomes. Middle – Quiescent Zone, does nothing unless a part is injured, replaces injured part. Bottom produces root cap cells. 3 primary meristomes – protoderm (makes epidermis), ground meristem( makes ground tissue), procambium (makes vascular tissue) Root cap – covers root tip which protects apical meristem. Secretes slime which lubricates abrasive soil. Zone of Cell Division (bottom) – Zone of Elongation – Zone of Maturation (top) page 721 Zone of Cell Division – mitosis, apical meristem, Zone of Elongation – root cells elongate, 10x’s their length o . pushes root further into soil Zone of Maturation – Root cells specialize in structure and function, Root Hairs Dicot Root – Stele contains xylem and phloem, xylem is spokes and phloem in between spokes. Monocot Root – Central chore of parenchyma cells (pith) surrounded by alternating rings of xylem and phloem Endodermis – One cell thick boundary of vascular cylinder (inner layer of cortex) Pericycle – gives rise to lateral roots (must grow from pericycle b/c nees to remain connected to vascular cylinder) Primary Growth in Shoots Page 723 Most of elongation occurs by growth of slightly older internodes below shoot apex due to cell division and elongation within the internodes In dicot stems vascular bundles arranged in a ring, xylem faces pith, phloem faces cortex (ground tissue near outer layer) In monocot stems, bundles are scattered throughout ground tissue. Cortex and pith don’t exist, just ground tissue. Epidermal layer has stoma which is flanked by two guard cells, allow CO2 exchange and evaporation. Mesophyll (middle of leaf) has mostly parenchyma cells for photosynthesis . Palisade Mesophyll – tight layers of elongated cells on upper part of leaf
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This note was uploaded on 04/07/2008 for the course BIO 51 taught by Professor Brunell during the Spring '08 term at Pacific.

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Chapter 30 - Chapter 35 Primary vs Secondary Growth...

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