Title: Vegetative (Asexual) Propagation
1Vegetative (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
2All 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)
3Cuttings 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
4The 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
5Redifferentiation requires
- Cells competent to form a root meristem (root
initial) - Development of a root initial into a functioning
root (determinism)
6Plants 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)
7Types 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)
8Preformed 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)
9Wound-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
10Both 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
11Origin 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)
12Time 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.
13Callus 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
14From Fig. 9-10, Hartmann 2002
15From Fig. 9-10, Hartmann 2002
Root Initials
apex organization
Root Primordium
differentiation, vascular connections
Root Emergence