Germination

Question 1

Define germination.

Answer 1

The process in which a plant grows from a seed. Begins with vigorous biochemical and developmental activity and ends when the first photosynthesising leaves are made.

Question 2

What are the 3 main requirements for germination?

Answer 2

Temperature - optimum temp for enzymes
Water - mobilises enzymes for transport in the xylem and phloem and makes cells turgid
Oxygen - aerobic respiration releases energy to fuel growth

Question 3

Describe the first stage of germination.

Answer 3

Seed imbibes water rapidly through micropyle - tissues swell and enzymes work - food reserves are insoluble so broken down into soluble molecule - amylase hydrolyse starch into maltose - protease hydrolyse proteins into amino acids.

Question 4

Describe the second stage of germination.

Answer 4

These products are taken to the apical meristems of the plumule and radicle - cell division occurs - sugars converted to cellulose for cell wall synthesis - aerobic respiration releases energy from sugars and amino acids used to synthesis proteins

Question 5

Describe the third stage of germination.

Answer 5

Swollen tissue ruptured testa and radicle emerges growing downwards - pumule emerges and grows upwards

Question 6

Describe the fourth stage of germination

Answer 6

Cotyledons of broad beans remain underground - plumule grows upwards in the shape of a hook to prevent tip being damaged by soil - hook then straightens and leaves unfurl and begin to photosynthesise - food reserves depleted.

Question 7

What happens to the dry mass of the embryo, seed and cotyledons?

Answer 7

Embryo = increases
Cotyledons = decreases
Seed = increases overall.

Question 8

Describe how giberellin works.

Answer 8

1. Embryo secreted giberellic acid which diffuses through the endosperm to the outside layer of cells called the aleurone layer.
2. The GA switches on genes resulting in production of enzymes including protease and amylase
3. Protease = proteins to amino acids - used to make amylase
4. Amylase diffuses out and hydrolysed starch in the endosperm
5. Maltose and glucose produced diffuse to the plumule and radicle
6. They are respired for energy, which fuels biosynthesis and cell division, bringing seeds out of dormancy.