Plant Structure, Growth, and Development

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Plant Structure, Growth, and Development

• Introduction
• The Angiosperm Body
• Plant Growth

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Introduction to Modern Plant Biology

• Molecular biology is identifying crucial genes
  (flower development) giving a better
  understanding of processes such as water flow,
  disease resistance, shoot and root control
• Structure and function is a key theme

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The Angiosperm Body

• Problems to be solved gravity, light, water
  transport, reproduction, and desiccation
• Root and shoot systems

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The Root System

• Functions anchor, store food, absorb and conduct
  water and minerals
• two types taproot and fibrous root systems
• role of root hairs
• mycorrhizae
• adventitious roots form above ground from stem
  or leaf

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The Shoot System

• Stems, leaves and flowers
• growth occurs at apex
• apical dominance has evolutionary importance
• underground stemsbulbs and rhizomes(potatoes)-sto
  re food
• leaves main photosynthetic organ

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Types of Plant Cells

• Function determined by protoplast and cell wall
  adaptations
• five types of plant cells
• 1. Parenchyma-synthesis and storage
• 2. Collenchyma-support in young plants
• 3. Sclernchyma-thick secondary walls, lack
• protoplast in mature cells?, supportive
• 4. Xylem-water conduction, two types
• tracheids and vessel elements
• 5. Phloem-food conduction

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Tissue Systems

• Three tissue systems dermal, vascular and ground
  tissues
• Dermal-single outside layer
• Vascular-xylem and phloem, transport and support
• Ground-between dermal and vascular, storage,
  synthesis, and support

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Plant Growth

• Meristems generate cells two types apical and
  lateral
• genetically determined life spans (most)
• annuals and perennials
• plants exhibit indeterminate growth
• two types of growth primary and secondary

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Root Growth

• Primary growth divided into three zones
• 1. Cell division apical meristem, this
  differentiates into protoderm, procambium, and
  ground meristem (primary tissues)
• 2. Cell elongation elongate at least 10X,
  pushes tip through the soil
• 3. Maturation cells complete their
  differentiation

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Primary Tissues in the Root

• Protoderm outermost layer of primary meristem,
  give rise to epidermis, many with root hairs
• Procambium forms stele (central cylinder)
  containing xylem and phloem,
• Ground meristem cortex between stele and
  epidermis, parechyma cells, stores food,
  endodermis single cell layer boundary between
  cortex and stele, pericycle inside endodermis

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Primary Growth of Stems

• Apical meristem forms primary meristems
  (protoderm, ground meristem, and procambium)
• Procambium forms vascular tissue in bundles
• Ground meristem forms pith and cortex
• Protoderm forms epidermal tissues

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Leaf Growth

• Ground tissues form the mesophyll
• procambium forms the veins
• Protoderm forms the upper and lower epidermis,
  guard cells waxy cuticle

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Secondary Growth

• Produced by growth in diameter
• results from vascular and cork cambium
• vascular produces xylem and phloem
• cork cambium produces covering of roots and stems
  that replace epidermis
• occurs in all gymnosperms and most angiosperms,
  rare in monocots

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Stages of Differentiation

• Apical meristem
• differentiates into protoderm, ground meristem,
  and procambium
• protoderm differentiations into epidermal
  structures
• procambium differentiates into the vascular
  tissues
• ground meristem produces tissues that fill in
  between the epidermis and vascular tissues

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Secondary Growth in Stems

• Vascular cambium produces secondary vascular
  tissues xylem--forms wood phloem--contributes
  to the formation of bark and sloughs off
• cork cambium produces the periderm (protective
  coat of plant, combination of cork cambium,
  layers of cork, and phelloderm,)
• bark-all tissues external to the vascular cambium
  

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Secondary Growth in Roots

• Vascular cambium produces secondary xylem to the
  inside and secondary phloem to the outside
• cortex and epidermis split and are shed as the
  stele increases in diameter
• very similar to stems, produces annual rings