L6 and 7 Claire Grierson - Roots

Question 1

What are 3 important roots?

Answer 1

Sugar beet - 85% sugar in UK. Extra beet used to make bioethanol.
Madder - root crop used for clothing dye
Gin seng - Medicinal root, ‘neutroceutical’

Question 2

How is phosphate polluting?

Answer 2

it is a key nutrient needed for plant growth, so is applied to fields. 98% of all phosphate applied to fields ends up in the ocean.

Question 3

How much pollution does agriculture cause in china?

Answer 3

50% of all pollution, 85% in rural places.

Question 4

What can cause lodging?

Answer 4

Corn root worm larvae, destroys maize root systems.

Question 5

what are some interactions between underground communities of roots?

Answer 5

competition for nutrients and water
cooperation to release nutrients
communication about pathogens and pests

Question 6

What is: the tap/embryonic/primary root
lateral roots
Basal roots

Answer 6

Tap/embryonic root - first to emerge from seed
lateral roots - extend off embryonic root
Basal roots - emerge off hypocotyl

Question 7

what effect does low phosphate have on a plant?

Answer 7

• Primary root growth strongly inhibited
• Root hair production and length increased
• More lateral roots form and grow longer.

Question 8

How can phosphate uptake be increased?

Answer 8

Increase root absorption surface.
favouring foraging of topsoil where phosphate accumulates
can adapt crop phenotypes to low phosphate conditions.

Question 9

What are 4 disadvantages to using nitrate as a fertiliser

Answer 9

1. v soluble in water and dangerous if in water supply eg in California, dangerous levels, causes blue baby syndrome.
2. v costly to produce
3. inefficient - half of all nitrate applied is not taken up by plants. Farming causes >half of N2 pollution in europe.
4. destroys symbiosis between mycorrhizae and plant - in high N, trees reduce C allocation to fungus. Can take 2-15 years to recover

Question 10

Who argues that roots arrived before soil and why?

Answer 10

Paleobotanists - Tree roots are needed for soil to accumulate, and plants increase weathering of rock. Dead plants gave structure and provided habitats.

Question 11

How may soil have evolved (timeline?)

Answer 11

Ordovician - bare rock
Silurean - small plants, cooksonia, small hairs act as very shallow roots. build up of soil material which is periodically washed away by floods, can be seen in fossil record.
End Devonian - huge forests and deep soil

Question 12

Which is the oldest fossilised forest and what species were there?

Answer 12

Gilboa, in NY area.
3 tree sized species: Eospermatopteris (non woody), Aneurophytalean (Woody climber), Lycopsida (giant club moss).
Leafless plants so only a partial shading

Question 13

Describe the environment in the first forests

Answer 13

Rich habitat, much food and water
in Carboiferous
Stable environment, not continuously flooded and washed away.

Question 14

How many organisms live in soil#?

Answer 14

6000 species per gram of soil

Many <0.05mm

Question 15

What is one of the most important organisms in the soil and why?

Answer 15

Fungi
Decomposers
export nutrients in forms other organisms can use
Many essential nutrients in our diet are fixed by fungi.
70% plants symbiotic
Mycelia holds soil together

Question 16

What is a mycorrhiza and What 2 types of mycorrhiza are there?

Answer 16

Fungi with a symbiotic relationship with land plant

Ecto mycorrhizae and endomycorrhizae.

Question 17

describe ectomycorrhizae

Answer 17

Ectomycorrhizae- eg Paxillus involitans, a poisonous mushroom forms ectomycirrhizae with numerous tree species.
fungus receives fixed C and provides nutrients. Plat avoids sending C to enemy fungus.

Question 18

Describe endomycorrhizae

Answer 18

Endomycorrhizae - Vesicular arbuscular mycorrhizae (VAM). fungus penetrates cortical cells of roots, forming abusclesand vesicle structures surrounded by specially made plant membrane. found in 80% of plant families.

Question 19

How has the presence of roots allowed river banks to form?

Answer 19

Allowed deeper channels to form and a channelled sand bed, meandering rivers and muddy floodplains.
stabilised rivers and streams

Question 20

3 facts bout soil

Answer 20

can take over 1000 years for 1cm of topsoil to form
soil C is the largest terrestrial pool of C
5 tonnes of animal life can live in 1 ha of soil.

Question 21

How much soil erosion is there?

Answer 21

1/4 of vegetated land on earth is already degraded by human activity.
Soil loss in agricultural land dwarfs soil production with 12,000,000 ha fertile land lost to soil erosion
abundance of life supported by soil depends on soil organic C content, so ultimately depends on amount of fixed C by local plat life.

Question 22

How doesN fixaytion occur in legumes?

Answer 22

Root nodules house N fixing bacteria (rhizobia) in anaerobic environment. Carried out by nitrogenase.
CWDE of bacteria allow bacteria into cells, and bacteria establish. Root hairs bend in on themselves to trap bacteria inside, forming infection locus.
Leghaemoglobin is an O2 carrier and hemoprotein, which is found in N fixing root nodules in response toinfection of N fixing bacteria.