Topic 14.1 The Structure & Growth of Flowering Plants

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Topic 14.1The Structure Growth of Flowering
Plants

• Biology 1001
• November 4, 2005

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I. The structure of Flowering Plants

• The Plant Body
• Plants are multicellular organisms with organs
  and organ systems, tissues, and cells (see Fig.
  1.3)
• The three basic plant organs are roots, stems,
  and leaves
• They are organized into a root system and a shoot
  system
• The two systems are interdependent and each
  accesses a different part of the plants
  environment

Figure 35.2(!!)
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Plant Organs - Roots

• A root is an organ that anchors a vascular plant,
  absorbs water and minerals, and may store organic
  nutrients
• Root hairs increase the surface area of the root
  for absorption
• Variations of a theme taproots, lateral roots,
  fibrous roots, storage roots, aerial roots,
  adventitious roots

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Plant Organs - Stems

• A stem is a shoot organ consisting of alternating
  nodes and internodes that supports leaves and
  flowers
• Axillary buds are located at the apexes of leaves
  and have the potential to form lateral shoots
  (branches)
• The terminal bud contains developing leaves and a
  compact series of nodes and internodes, and is
  the site at which most shoot elongation occurs
• Stem variations include stolons, bulbs, tubers,
  rhizomes

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Plant Organs - Leaves

• The leaf is the main photosynthetic organ of most
  plants, and consists of a blade and petiole
  (stalk)
• Flowers, the reproductive organs of flowering
  plants, are shoots composed of highly modified
  leaves and stems
• Leaves also contain veins of vascular tissue
• Leaf morphology and venation pattern are used to
  classify plants
• Modified leaves include tendrils, spines, storage
  leaves, bracts, and reproductive leaves

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Plant Tissues Systems

• Each plant organ has dermal, vascular and ground
  tissue systems
• These tissue systems are continuous throughout
  the plant and connect the organs
• The dermal tissue system is the outer protective
  covering of the plant usually a single layer of
  tightly packed cells called the epidermis
• The vascular tissue system contains xylem
  phloem which are used for long-distance transport
  in the plant
• The ground tissue functions in storage,
  photosynthesis, and support

Figure 35.8(!) The three plant tissue systems
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Plant Cells

• Fig. 6.9 - a generic plant cell
• Like other multicellular organisms, plant cells
  are differentiated into specialized types with
  particular functions
• Differentiation can be at the level of the
  protoplast (living part of the cell) or at the
  level of the cell wall
• Plant cells can have primary and secondary cell
  walls
• Plants cells can be living or dead at functional
  maturity

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Figure 35.9(!) - Exploring Examples of
Differentiated Plant Cells

• Parenchyma cells are living cells with flexible
  primary cell walls, large vacuoles, and no
  secondary cell walls
• They are the least differentiated of plant cells
  and perform most of the metabolic synthesis and
  storage functions of the plant
• They retain the ability to divide and
  differentiate into other cell types
• Examples include photosynthetic cells, the fleshy
  part of a fruit, and cells that store starch in
  plastids

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Figure 35.9(!) - Exploring Examples of
Differentiated Plant Cells

• Collenchyma cells are living cells with unevenly
  thickened primary walls that remain flexible
• Grouped in strands or cylinders, they provide
  support for a young growing plant

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Figure 35.9(!) - Exploring Examples of
Differentiated Plant Cells

• Sclerenchyma cells are dead at functional
  maturity, and they have thick secondary cell
  walls strengthened with lignin
• They support the non-growing parts of the plant
• Sclereids and fibers are two types of
  sclerenchyma cells

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Figure 35.9(!) - Exploring Examples of
Differentiated Plant Cells

• Phloem contains two types of sugar-conducting
  cells called sieve-tube members and companion
  cells
• Both types are alive at functional maturity
• Sieve-tube members lack organelles, and are
  connected end-to-end to form sieve tubes with
  porous sieve plates at the ends of each cell.
  These are the cells that conduct organic
  nutrients
• Companion cells are adjacent to sieve-tube
  members and perform the metabolic functions for
  both cell types they also function to load
  sugars into the sieve tubes

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Figure 35.9(!) - Exploring Examples of
Differentiated Plant Cells

• Xylem contains two types of water-conducting
  cells called tracheids and vessel elements
• Tubular, elongated cells with thickened secondary
  walls that are dead at functional maturity and
  act as conduits for the flow of water
• Tracheids are thin tapered cells whose secondary
  walls are thickened by lignin water moves
  laterally between tracheids via pits
• Vessel elements are connected end-to-end to form
  vessels. Water moves into vessel elements
  laterally via pits, and then flows vertically
  through porous end plates