Lecture 18: Grafts and Wounds

Question 1

What is grafting?

Answer 1

A set of techniques for joining together 2+ plant parts from different plants so they grow as 1 (makes a chimera)

Question 2

What is a chimera?

Answer 2

2 different plant genotypes are growing together in the same plant

Question 3

An example of a chimera?

Answer 3

The roots of an apple tree in a commercial orchard came from a plant with a disease resistant and dwarfing genotype while the shoot has a genotype exhibiting great tasting apples.

Question 4

What is a scion?

Answer 4

Genotype intended for the above-ground part of the plant

Question 5

What is a rootstock?

Answer 5

Genotype intended for the below ground bit of the plant

Question 6

What is budding?

Answer 6

Grafting technique where the scion is a bud with the genotype intended for the above ground part

Question 7

7 reasons why a horticulturist would graft (as many as you can)

Answer 7

1) Create unique, commercially desirable ornamentals
2) Perpetuate desirable genotypes of plants that are notoriously tough to root
3) Change varieties or cultivars
4) Produce trees with specialized forms (like weeping habit)
5) Increase growth rate of seedlings
6) Repair damaged palnts
7) Take advantage of rootstock characteristics (like dwarfing)

Question 8

Examples of plants that have difficulty rooting:

Answer 8

Japanese Maple, conifer

Question 9

Why would someone want to change varieties or cultivars?

Answer 9

Apple tree’s apples are no longer commercially desirable. (More time and cost efficient than digging up and replanting)

Question 10

2 reasons against grafting

Answer 10

1) Requires experience in technique

2) Must need a good reason to graft and no easier or cheaper way to do it.

Question 11

2 things that happen when you do a stem cutting:

Answer 11

1) sells along cut a sliced open, die, and become necrotic tissue
2) surviving cells (typically parenchyma) one layer in from the cut respond to the wound

Question 12

2 cell responses to the wound:

Answer 12

1) cells rapidly exclude compounds like suberin to protect plant from excess water loss and invasion by disease or insects (takes hour)
2) cells are stimulated to divide and produce a mass of new cells to cover and protect wound- called callus (takes years)

Question 13

What cells does the callus originate from?

Answer 13

Parenchyma cells in pith, phloem, or xylem regions(depends of species) in both scion and rootstock

Question 14

What is a callus bridge

Answer 14

Callus from rootstock and scion grow together

Question 15

What makes cell differentiation quicker in a graft?

Answer 15

Close alignment of cambium in scion and rootstock

Question 16

5 requirements of a successful graft:

Answer 16

1) The rootstock and scion must be compatible
2) Cambial layers must be closely aligned
3) Graft must be done at the appropriate time
4) Grafts must be protected from drying
5) The grafted plant must receive proper aftercare

Question 17

Why is dwarfing desirable in apple trees?

Answer 17

The standard apple tree can grow to be 40-50 feet tall.

Question 18

Common grape pest

Answer 18

grape phylloxera (invasive, root eating, aphid-like pest

Question 19

What saved the French wine industry?

Answer 19

Grafting V. Vinifera scion to resistant rootstocks

Question 20

What is the vegetable grafting technique done with?

Answer 20

Two week old seedlings