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BLGY2163 How plants Work > Seeds > Flashcards

Seeds Flashcards

1
Q

What are the 3 stages in grain filling?

A
  1. Embryogenesis
  2. Maturation
  3. Drying to 10% moisture content
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2
Q

What is imbibition?

A

Rehydration

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3
Q

What is seed maturation controlled by?

A

ABA, sucrose and chromatin remodelling

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4
Q

Which seed type can be dried down?

A

Orthodox

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5
Q

What provides orthodox seeds with protection from desiccation damage?

A
  1. Synthesis of stress related sugars and proteins (heat shock proteins and LEA proteins)
  2. Protection of membranes and macromolecules
  3. Interactions between sugar and protein complexes stabilise their physical structure (sugars replace water).
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6
Q

How many storage reserve types will any one seed have?

A

2

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7
Q

What is the storage organ in non-endosperms?

A

Cotyledons, in plants with endosperms, it is this that is used in nutrient uptake

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8
Q

What are cotyledons?

A

Embryonic seed leaves

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9
Q

What is the hypocotyl?

A

Stem-like embryonic axis

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10
Q

What is the radicle?

A

The embryonic root

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11
Q

How does the seed take up nutrients since it has no direct vascular connection to the mother plant?

A

From the phloem into the maternal tissues by active transport into the apoplast and endosperm cavity.

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12
Q

Where is starch deposited?

A

In modified plastids called amyloplasts.

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13
Q

Give 4 storage proteins

A
  1. Albumins
  2. Globulins
  3. Prolamins
  4. Glutenins
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14
Q

What transports amino acids across the plasma membrane?

A

Amino acid permeases

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15
Q

What are the roles of APP1 and APP2?

A

APP1 - taking up amino acids into the endosperm

APP2 - Unleading amino acids from the maternal tissues into the apoplast

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16
Q

What happens in the 3 phases of germination?

A

1 - rapid increase in water content driven by osmosis, DNA repair
2 - Prepare for germination or desiccate again
3. Water uptake increases due to growth of new tissues

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17
Q

Give 3 environmental cues

A
  1. temp
  2. Light and light quality
  3. Chemicals such as nitrate and smoke
18
Q

Give 2 intrinsic capabilities

A
  1. Capacity to germinate? Viable

2. Weakening of seed coat

19
Q

What is the difference between dormancy and quiescence?

A

Dormancy: intrinsic property of a seed, will not germinate if internal signalling is telling it not to
Quiescence: low metabolic activity, germination isn’t possible due to low metabolic activity

20
Q

What is the gene which causes pre-harvest sprouting in maize?

A

Viviparious-1 (VP1)

21
Q

What does VP1 control?

A

ABA signalling pathway

22
Q

What does ABA do?

A

Inhibits germination and induces dormancy

23
Q

What happens in plants with the abi mutant?

A

ABA insensitivity so show reduced dormancy, can germinate in the presence of ABA

24
Q

What is Abi1?

A

A type 2C protein phosphatase which dephosphotylates a SNF-1 SnRK2 protein kinase so it cannot bind to the transcription factors and so ABA signalling is not possible

25
Q

What should happen in a WT plant in ABA signalling?

A

In the presence of ABA the receptor binds PP2C so it cannot dephosphorylate SnRK2 allowing signalling of ABA and preventing germination

26
Q

Which hormone stimulates germination?

A

Gibberellin

27
Q

What causes the formation of Pr?

A

Absorbance of red light (660nm) from previous exposure to far red light - represses dormancy

28
Q

What causes formation of Pf?

A

Absorbance of far red light (<660nm) from previous exposure to red light - breaks dormancy

29
Q

What does far red light do to levels of gibberellin?

A

Decreases the pool of active gibberelling so ABA can keep the seeds dormant

30
Q

What does red light do to the levels of gibberellin?

A

Increases the pool of active gibberellin by increasing transcription of GA3ox allowing active gibberellin (GA4) which decreases ABA synthesis

31
Q

Which gene controls the levels of gibberellin and ABA in seeds?

A

Delay of germination (DOG-1). Active DOG-1 increases the levels of dormancy.

32
Q

What releases a large amount of hydrolytic enzymes in reserve mobilisation?

A

Aleurone layer

33
Q

What is the scutellum?

A

Important in the mobilisation of reserves - good transport capacity

34
Q

How is insoluble starch converted to glucose?

A

Combined action of a-amylase, B-amylase, limit dextrinase and a-glucosidase

35
Q

What is PSV?

A

Protein storage vacuole

36
Q

When proteins have been broken down, where are they transported to?

A

From the endosperm to the embryo

37
Q

How are nucleic acids broken down?

A

NucleaseI forms mononucleotides and then acid phosphatases form mononucleosides (phosphate group)

38
Q

What seeds does the viability equation apply to?

A

Orthodox only as they respond in a quantifiable and predictable way

39
Q

What is Osmopriming?

A

Restriction of the amount of water that the seed can take up so germination cannot occur although pre-germination processes like DNA repair can

40
Q

What is hydropriming?

A

Continuous or successive addition of a limited amount of water to the seeds.

BLGY2163 How plants Work (5 decks)

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