Exam 2: Asexual Reproduction

Front 1

genet

Back 1

all the members of a genetically identical group

Front 2

ramet

Back 2

one individual of a genet

Front 3

types of natural vegetative reproduction in forest trees

Back 3

Stems Carry Roots Lovingly About

1. root Suckering
2. Coppicing (stump sprouting)
3. Rooting of detached branches
4. Layering
5. Apomixis

Front 4

types of natural asexual reproduction in forest trees

root suckering

Back 4

a form of budding that involves the reproduction or regeneration of a plant by shoots that arise from an existing root system

• shoot buds form on roots (in pericycle, rays, or phellogen) and elongate
  
• in our region: black locust, sweetgum, sumacs, sassafras
• in the west: quaking aspen (Populus tremuloides) forms huge clonal stands of root sucker origin

Front 5

types of natural asexual reproduction in forest trees

coppicing/stump sprouting

Back 5

type of natural reproduction in which dormant buds at root collar break and send up new shoots from stump

• might remind you of epicormic shoots
  
• sprouting from the root collar
  
• most hardwoods in our region are good at this
• most conifers are NOT good at it (exceptions are pond pine, pitch pine, shortleaf, and coast redwood)

Front 6

types of natural asexual reproduction in forest trees

rooting of detached branches

Back 6

when a branch becomes detached from plant, under the right conditions, it may root and form its own individual plant

• branches must land in wet, sandy soil, and then they can make adventitious roots (new roots not derived from radicle)
• can root into sandy soil
• cottonwood, willow, sycamore good at this (most other trees are not)

Front 7

types of natural asexual reproduction in forest trees

layering

Back 7

occurs when a branch that's still attached to tree touches ground or gets covered w/ organic matter (e.g. peat moss) and develops adventitious roots, then sends up new shoots

• attached branches reach ground and root
  
• spruces do this in Boreal forest sphagnum bogs
• in our region, un-pruned southern mags often layer

Front 8

types of natural asexual reproduction in forest trees

apomixis

Back 8

seed development without fertilization

• embryos form in seeds from unfertilized maternal tissues (e.g. nucellus) in addition to the zygotic embryo
• very common in Citrus species, but not in forest trees
• occurs in alder and at least one maple

Front 9

types of artificial vegetative propagation of woody plants: macropropagation

Back 9

Roots Rarely Get Air

1. Rooted stem cuttings
   
2. Root cuttings
3. Grafting
4. Air layering

Front 10

types of artificial asexual propagation in woody plants

macropropagation: rooted stem cuttings

Back 10

• steps:

1. take stem cuttings with or without leaves
   
2. trim leaves back to limit H2O loss
   
3. treat the cut end with a plant hormone (auxin)
4. stick the cut end in wet sand or potting mix, or even in soil outside
5. keep it moist
   
6. wait for days or weeks
   
7. cut ends will make adventitious roots
   

• easy with some trees (cottonwood), very hard with other trees (oaks, pines)
• very young trees are easy to root; older trees are harder to root
  

Front 11

types of artificial asexual propagation in woody plants

macropropagation: root cuttings

Back 11

• steps:

1. dig up roots of tree
   
2. cut them up into segments (4-6 inches long)
   
3. rebury them in sandy soil
   
4. root segments will make new roots and new shoots
   

• works best for trees well-known for root suckering (e.g. black locust, sweetgum)
  

Front 12

types of artificial asexual propagation in woody plants

macropropagation: grafting

Back 12

• scions (shoots) from one tree are grafted onto root stocks (stems or stumps) of other trees
• grafting is an “art”
• used for thousands of years to clonally propagate fruit and nut trees
• in forestry, used to generate clonal pine seed orchards —probably 90% of grafting in forestry is for pines
  

Front 13

types of artificial asexual propagation in woody plants

types of artificial vegetative propagation of woody plants: micropropagation

Back 13

1. in vitro propagation/tissue culture
   

Front 14

types of artificial asexual propagation in woody plants

micropropagation: tissue culture / in vitro propagation

Back 14

• steps:

1. take cells or tissues of trees and grow them on medium with plant growth regulators, nutrients and sugar
   
2. tissue culture treatment causes them to make new shoots that can be rooted or embryos that can be germinated
   

• works with both hardwoods and conifers
• about 15 million southern pines planted each year are “somatic seedlings” derived from tissue culture...called "clonal" or "varietal" forestry