Vegetative (Asexual) Propagation - PowerPoint PPT Presentation

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Vegetative (Asexual) Propagation

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Vegetative (Asexual) Propagation Used extensively (in hort) to propagate plants that aren t easily propagated by seed Kinds of vegetative propagation – PowerPoint PPT presentation

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Title: Vegetative (Asexual) Propagation


1
Vegetative (Asexual) Propagation
  • Used extensively (in hort) to propagate plants
    that arent easily propagated by seed
  • Kinds of vegetative propagation
  • Cuttings
  • Layering
  • Tissue culture
  • Specialized structures (bulbs, etc.)
  • Grafting and budding

2
All vegetative propagation methods use a piece of
one plant (propagule) to reproduce another
(identical) plantAll plants that are propagated
from one original plant are part of a clone
(clonal propagation)
3
Cuttings are (in general) the easiest, the
cheapest, and the most widely used forms of
vegetative propagationStem cuttings are the
most common type of cutting used
4
The goal in propagating by stem cuttings is to
replace the missing part (root system)Two
processes are required
  • Dedifferentiation - the ability of a
    differentiated cell to initiate cell division
  • Redifferentiation - formation of a growing root

5
Redifferentiation requires
  • Cells competent to form a root meristem (root
    initial)
  • Development of a root initial into a functioning
    root (determinism)

6
Plants from which stem cuttings can be taken
  • Annuals, biennials, herbaceous perennials (most
    are easy-to-root)
  • Woodies (range from easy-to-root to hard-to-root)

7
Types of rooting on stem cuttings (based on the
type of roots that develop)
  • Preformed roots and latent root initials -
    present when the cutting is taken from the stem
  • Wound-induced roots - not present when the
    cutting is made (cutting the stem into pieces
    causes a wound reaction that stimulates rooting)

8
Preformed roots or latent root initials
  • Develop while still attached to the parent plant
  • Usually lie dormant till stems are made into
    cuttings
  • Are often associated with nodes
  • Are common in certain genera (e.g., Salix,
    Hydrangea, Ribes, Populus)

9
Wound-induced roots (anatomical events)
  • Dedifferentiation - differentiated cells prepare
    to divide
  • Formation of root initials from dividing cells
  • Root primordia formation - the apex becomes
    organized
  • Root emergence through the stem

10
Both wound-induced and preformed roots are
adventitious
  • New (de novo) growing points (root meristem) form
    on established structures (e.g., a stem)
  • Roots arise other than by normal development of
    the seedling
  • Or, simply - a root developing where one isnt
    expected

11
Origin of adventitious roots in a stem
  • Herbaceous near a vascular bundle
  • Woodies
  • Easy-to-root species (spp.) near the vascular
    cambium directly
  • Hard-to-root spp. often requires an intervening
    callus phase (indirectly)

12
Time of adventitious root formation in juvenile
and mature leaf-bud cuttings of Ficus pumila
treated with IBA
Davies FT et al. (1982) Amer J Bot 69804-811.
13
Callus and rooting
  • Callus is an irregular mass of dividing
    parenchyma cells
  • Relationship to rooting
  • Formation of callus and roots are independent
    events in easy-to-root spp.
  • Callus formation is often a precursor to root
    formation in hard-to-root spp

14
From Fig. 9-10, Hartmann 2002
15
From Fig. 9-10, Hartmann 2002
Root Initials
apex organization
Root Primordium
differentiation, vascular connections
Root Emergence
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