CHAPTER 35 PLANT STRUCTURE

1
CHAPTER 35 - PLANT STRUCTURE GROWTH

• I. Plant (Anthophyta) Body Structure
• A. general morphology - 2 main systems
• 1. root system - functions to anchor the
  plant, absorb minerals water, conduct water
  nutrients, store food tissue lacks
  chloroplasts root hairs near the tips
  facilitate absorption some plants have
  adventitious roots

2
2 plant systems (cont.)

• 2. shoot system - consists of 3 organs
• a. stems - function to support position
  the leaves many plants have modified stems
  (stolons, rhizomes, tubers, bulbs) with
  modified functions
• b. leaves - main photosynthetic organ many
  plants with modified leaves (tendrils, spines,
  etc.)
• c. flowers - discussed in Ch. 38

3
B. anatomy

• 1. 7 specialized plant cells
• a. parenchyma cells - the typical plant
  cell relatively unspecialized carry out much
  of the plants metabolism
• b. collenchyma cells - have thicker primary
  walls help support young part of the plant
  without restraining growth

4
7 plant cells (cont.)

• c. sclerenchyma cells - thick secondary walls
  usually strengthened by lignin supports the
  plant dead at maturity two forms fibers
  sclereids
• d. tracheids - have secondary walls hardened
  with lignin dead at maturity long thin with
  tapered ends conduct water provide support

5
7 plant cells (cont.)

• e. vessel elements - like tracheids but wider,
  shorter, thinner-walled, less tapered end
  walls are perforated
• f. sieve-tube members - alive at maturity but
  lack major organelles porous end walls called
  sieve plates transport food
• g. companion cells - support the sieve- tube
  members may help load sugar

6
2. 3 tissue types

• a. dermal tissue (epidermis) - single layer of
  tightly packed cells that protects the plant
  gives rise to root hairs secretes the cuticle
  on the shoot
• b. vascular tissue (xylem phloem) -
  transports water nutrients and provides
  support
• c. ground tissue - everything else made up
  primarily of parenchyma

7
II. Plant Growth

• A. primary growth - elongation
• 1. root
• a. zone of cell division - apical meristem
  ( derivitives) region of mitosis protected
  by root cap
• b. zone of elongation - elongation of cells
  which pushes the root tip forward
• c. zone of maturation - cells begin to
  specialize

8
2. stem primary growth

• a. apical meristem - at the tip of the terminal
  bud is the main region of mitosis elongation
  occurs by growth (both cell division and
  elongation) of slightly older internodes below
  the tip
• b. axillary buds - formed by left over
  islands of apical meristem can form a side
  branch, but usually inhibited by the terminal
  bud apical dominance

9
B. secondary growth - increasing girth

• 1. roots - 2 lateral meristems
• a. vascular cambium - forms within the stele
  and produces secondary xylem to its inside and
  secondary phloem to its outside cortex
  epidermis are split and shed
• b. cork cambium - forms from the pericycle and
  produces periderm which replaces epidermis

10
2. stem secondary growth

• a. vascular cambium - a meristematic layer that
  develops between primary xylem phloem and
  which produces secondary xylem (wood) to its
  interior and secondary phloem to its exterior
• b. cork cambium - a meristematic layer that
  forms in the outer cortex and which produces
  cork to replace the sloughed epidermis ?
  periderm

11
III. Monocots vs. Dicots

• A. monocots - one of two classes in
  Anthophyta examples lilies, orchids, yuccas,
  palms, grasses (including lawn grasses, sugar
  cane, grains)
• B. dicots - one of two classes in Anthophyta
  examples roses, peas, buttercups,sunflowers,
  oaks, maples

12
Monocots vs. Dicots (cont.)

• arrangement of vascular bundles in the root
  monocot in a ring vs. dicot in an X
• shape of guard cells monocot - dumbbell vs.
  dicot - kidney

13
Monocots vs. Dicots (cont.)

• In monocots endosperm provides nutrition to
  germinated seedling. In dicots the nutritive
  function is transferred to the cotyledons.
• During germination the monocot shoot pushes
  straight up, while the dicot shoot tip is pulled
  up by a hook in the embryonic axis.