Wood Decay

Question 1

What are the components of wood?

Answer 1

• cellulose ( glucose chains - 10,000 )
• Hemicellulose ( branched sugars - 1,000)
• Lignin (3D, amorphous polymer)
• Extractives (phenolics and other compounds)

Question 2

How is lignin arranged in wood?

Answer 2

lignin is arranged in such a way that it encapsulates cellulose and hemicellulose.

Question 3

Can all fungi decay wood?

Answer 3

No, only a few can

Question 4

What enzymes break down cellulose

Answer 4

cellulase (endo and 2exo)

• exocellulase works on the ends of cellulose chains. different type for each end of the chain.
• endocellulase breaks chain into more pieces for exocellulase to break down.

Question 5

What enzyme breaks down lignin

Answer 5

lignase

Question 6

What is a distinguishing characteristic of white rot fungi?

Answer 6

produce cellulase + lignase. white rot completely breaks down wood substrate.

Question 7

What is a distinguishing characteristic of brown rot?

Answer 7

Only produce exocellulase
-also produces hydrogen peroxide and Iron (3) oxide which emulate endocellulase by entering wood through pores in lignin, breaking cellulase chains apart. This action widens the pores which allows for exocellulase to penetrate and break down cellulose. Lignin left over.

Question 8

What are the purpose of extractives in trees?

Answer 8

extractives are poisons produced by trees that prevent colonization by fungi.

Question 9

What distinguishes heart rots?

Answer 9

target live trees only

Question 10

what are the 2 types of heartrot and how do they infect trees?

Answer 10

1. Trojan horse (true heartrots): colonize tiny wounds caused by broken branches (tertiary stubs) and lie dormant until tree grows over it. When tree becomes stressed, they emerge from dormancy.
2. Wound Invaders: can be separated into 2 groups:
   Primary - need fresh wound to colonize
   Secondary - can invade wounds that have already been colonized

Question 11

What are the characteristics of true heart rots?(5)

Answer 11

• no wound necessary
• heartwood only
• conks on live trees
• never invade slash
• die after tree dies

Question 12

What are the characteristics of wound invader heart rots?(5)

Answer 12

• mainly heartwood
• conk seldom on live tree
• some invade slash
• lives after tree dies
• around 38 species.

Question 13

What are the characteristics of sap rots?(3)

Answer 13

• saprophytes
• decay dead sapwood
• a.k.a slash rots

Question 14

What do gills on the bottom of a conk tell you?

Answer 14

Slash conk

Question 15

live trees decay from…

dead trees decay from…

Answer 15

live trees, inside out. (sapwood contains living defense mechanisms)
dead trees, outside in (sapwood defences are non functional)

Question 16

Which fungi groups decay by digestion?

Answer 16

Basidiomycetes (White rots and brown rots)

Question 17

What is the end result of brown rots? (4)

Answer 17

• Early in decay
• quick loss of strength
• quick loss of pulp yield
• brown and cubical end product (only lignin left)

Question 18

What trees do brown rots target in general?

Answer 18

primarily conifers

Question 19

What are the end result of white rots? (4)

Answer 19

• White due to bleaching and removal of lignin
• Localized (pockets)
• surrounding wood intact
• maintains strength and pulp yield for longer.

Question 20

What trees do white rots generally target?

Answer 20

-conifers and hardwoods both.

Question 21

Where are the locations a tree can be decayed from?

Answer 21

• Top rot
• Stem rot
• Butt rot
• Root rot

Question 22

What are some examples of true heart rots?

Answer 22

Phellinus tremulae (black cracked top)
Echinodontium tinctorium (hemlock)
Phellinus pini (fir pine spruce)

Question 23

What is an example of a wound invader?

Answer 23

Annosus (black flecks scattered throughout rotten wood)

Question 24

What is an example of a sap rot?

Answer 24

Slash conk (gills on conk)