Lec 6 - Root Foraging

Question 1

phenotypic plasticity

Answer 1

Ability to change how ones genes are expressed

Question 2

Strategies for dealing with patchy resources

Answer 2

-Physiological Adjustment
Existing roots increase nutrient uptake rates
Good strategy for nutrients that are patchy in time

-Selective root death
Allow unproductive roots to die back

-Root proliferation
Grow more roots in the right places

Question 3

Advantages of physiological adjustment

Answer 3

-Fast (response in minutes to hours)
-Effective for capturing ephemeral
resources (e.g. urine patch)
-No need to spend energy on
building new roots

Question 4

Disadvantages of physiological adjustment

Answer 4

The plant has to have roots in the
right place, cannot reach new
patches
Cannot displace competitors

Question 5

Advantages of changing root demography

Answer 5

-live roots cost energy to maintain, so energy saved by eliminating less productive ones
• Fine roots turn over rapidly anyway; adjusting timing of death is straightforward

Question 6

Disadvantages of changing root demography

Answer 6

-Relatively slow relative to physiological adjustment

• Loss in investment when roots turned over

Question 7

Net change =

Answer 7

births + deaths

Question 8

Root proliferation

Answer 8

-Rapid production of
new roots in nutrient
rich patches
-First studied using
hydroponic systems
-Occurs in response to N and P

Question 9

Strategies for dealing with patchy resources

Answer 9

First nutrient uptake rate increased,

Then increased root proliferation in enriched zone.

Question 10

When in competition:

Answer 10

Root proliferation
was more important
than an increase in N
inflow rates.

Plants obtained more
nitrogen from the
patch when they had
more roots there.

Question 11

How can a plant sense another root is there?

Answer 11

Detection of chemical signals
Plant roots release many secondary metabolites and
proteins which other roots may take up.