Lecture 10

Question 1

Arbuscular mycorrhiza importance

Answer 1

important in most ecosystems

-most grassland plants, many tropical rain forest trees, some temperate woodland trees

Question 2

where do ectomycorrhiza form

Answer 2

most boreal forest trees, and many temperate forest species

Question 3

Arbuscular mycorrhiza in crop plants

Answer 3

lots! (cereals, peas,onions)

NOT found in oilseed rape, cabbages, mustard, sugar beet and quinoa etc

Question 4

mycorrhizal fungi and passing of carbon

Answer 4

~12% of the terrestrial C cycle passes from plants to mycorrhiza

Question 5

Arbuscular mycorrhiza hyphal lengths

Answer 5

10-100X long than roots

• in cereal crops typically rand 2-8m/g soil
• permanent grasslands 45-74 m/g soil many records

Question 6

hyphae affect on soil

Answer 6

• effect microbiome of soil round roots (suppressing pathogens, supporting and eliciting plant growth promoting rhizobacteria)
• effect soil structure

Question 7

primary function of mycorrhiza

Answer 7

• enhance ability to take up phosphorous
• esp Arbuscular mycorrhiza
• small hyphae diameter, as can enter pores in soil smaller than a root hair can
• exploit areas of nutrients

Question 8

___ affinity P uptake in mycorrhizal compared to non-mycorrhizal plants of the same species

Answer 8

higher

Question 9

which is faster: translocation down hyphae to roots (P H–> R C R–>H) or diffusion of P in solution

Answer 9

translocation down hyphae to roots (P H–> R C R–>H)

Question 10

AM hyphae extend up to __ more than root hairs

Answer 10

up to 11cm or more

-allow to explore depletion zone (extend)

Question 11

how do mycorrhizas increase P uptake by plants? evidence of use of organic P sources

Answer 11

Tarafdar & Marschner 1994

Jayachandan et al 1992

Question 12

acid phosphatase activity is ___ around roots of mycorrhizal compared to non-mycorrhizal plants of the same species

Answer 12

higher

Question 13

mycorrhizal saving fertiliser?

Answer 13

arbsucular mycorrhizal (cassava) grows in P deficient tropical soils

Question 14

key to mycorrhizal success:

Answer 14

dependent on plant and fungal characteristics

-different species show diff responses to mycorrhiza

Question 15

different plant species responses to mycorrhiza

Answer 15

costs & benefits are not shared equally between plants and are fungus specific
-some they don’t benefit some they do (some even suppress if they inhibit roots)

Question 16

root length density effected by tillage?

Answer 16

No tillage increases root length particularly close to surface

Question 17

cereal crops hyphae ____ km/ha to 10 cm depth

Answer 17

2 - 8 million KM

HUGE

Question 18

ploughing’s effect on mycorrhizal infection in roots

Answer 18

just one occurrence of ploughing has a major negative impact, direct drilling is the only option to not effect it

Question 19

hyphae & soil aggregation

Answer 19

hyphae play a role in holding water (glomalin protein) and aids in storing organic carbon

Question 20

mycorrhiza always get greater yields?

Answer 20

not necessarily, ploughed and disc cultivated wheat + mycorrhiza yields don’t increase, do when directly drilled though (58% increase) using less fertiliser

Question 21

how to gain highest corn yield work WITH nature not agains it =

Answer 21

the least energy requiring and highest yielding treatment =

- living clover clipped but not removed, no P fertiliser, no tillage

Question 22

diversity of mycorrhizal fungi species effect on P uptake and hyphal length

Answer 22

both increase w increased diversity

Question 23

hyphae growing inside plants =

Answer 23

induce systemic defences against shoot & root pathogens

-sooty mould of wheat

Question 24

good mycorrhiza hosts

Answer 24

legumes as cover crop

Question 25

what is “Round up”

Answer 25

glyphosate is a herbicide

-inhibits mycorrhiza spore germination

Question 26

mycorrhiza & sunflower weeds

Answer 26

they help to suppress weed biomass, both in weed spp. that form mycorrhiza and those that do not

Question 27

Agronomic practices: Favouring mycorrhiza

Answer 27

1) manure & compost
2) minimal tillage
3) low use of superphosphate fertiliser
4) mycorrhiza-compatible crops, cover crops and varieties
5) organic management
6) use of leys

Question 28

agronomic practices: Impairing mycorrhiza

Answer 28

1) low organic matter inputs
2) repeated inversion tillage
3) high use of P fertilisers
4) varieties and crops with low or no capacity to form mycorrhiza
5) high use of weed killers and fungicides
6) continous cultivation

Question 29

benefits of mycorrhiza, minimal tillage, growth of mycorrhiza-competent growth varieties, minimal use of agro-chemicals:

Answer 29

1) increase crop nutrient use efficiency
2) improved soil structure - macro aggregates that hold water, nutrients and organic matter and enable deep root growth
3) greater soil organic matter content of surface soil
4) increases populations of earthworms
5) improved soil drainage and micropore flows reducing risk of flooding and soil erosion
6) increased drought tolerance of crop
7) increased crop resistance to diseases and stimulation of plant growth rhizobacteria (PGPR)
8) suppression of weeds