R2101 3.2 Describe the structure and functions of fruits and seeds

Question 1

What is fertilisation?

Answer 1

The fusion of the male gamete from pollen with a female gamete in the ovule to produce the embryo

The nucleus of the male gamete (pollen) joins with the nucleus of the female gamate (ovule)

Question 2

What is a fruit?

Answer 2

1. A fruit is formed from the ovary after fertilisation.
2. In contain the seeds and occurs in a wide variety of forms
3. Fruit is designed to help with seed dispersal
4. The ovule becomes seeds, and the ovary wall swells to accomodate them as they develop.
5. Can be fleshy, dry, edible or spikey

Question 3

What is a seed?

Answer 3

A seed is formed from the ovule after fertilisation

Question 4

How many gametes does the male nucleus have?

Answer 4

Two

Question 5

What is the function of each male gamete?

Answer 5

1. One gamate travels down the pollen tube to fuse with the female gamete to form a zygote. Further development and cell division takes place and the zygote becomes an embryo - the basis of a new plant within a seed.
2. In many plants the second gamate fues with other cells in the ovule to form a food store for the developing seed - the endosperm

Question 6

What are pseudocarps?

Answer 6

False fruits that form from other parts of the flower, not the ovary

Question 7

Main fruit types (3)

Answer 7

1. Dry:
   Dehiscent (seed case splits)
   Indehiscent / hard (seed case remains intact)
2. Fleshy or succulent

Question 8

Succulent or fleshy fruits

Answer 8

1. Includes those that are typically eaten - apples, pears, cherries, tomatoes, cucumbers etc
2. Often have chemicals that prevent seeds germinating until all fruit pulp has been removed
   e.g. elderberry passed through the gut of a bird and pulp is disgested. Seed is then excreted far from the original plant with its own fertiliser package

Question 8

Succulent or fleshy fruits (2)

Answer 8

1. Includes those that are typically eaten - apples, pears, cherries, tomatoes, cucumbers etc
2. Often have chemicals that prevent seeds germinating until all fruit pulp has been removed
   e.g. elderberry passed through the gut of a bird and pulp is disgested. Seed is then excreted far from the original plant with its own fertiliser package

Question 9

Indehiscent dry fruits (3)

Answer 9

1. Nuts like hazel, sweet chesnut
2. Seeds like sunflower
3. Winged samaras like sycamore and ash

Question 10

Dehiscent fruits (2)

Answer 10

1. Seedcase of delphiniums , poppies split and release dry seed cases
2. Seed may be propelled a long way by the drying and twisting action of the seed pod

Question 11

What is the function of a fruit? (2)

Answer 11

1. The distribution and protection of the seed
2. In may impose dormancy

Question 12

What is the function of the seed? (3)

Answer 12

1. The distribution and protection of the embryo
2. In may impose dormancy
3. It gives rise to new plants

Question 13

How are seeds dispersed? (4)

Answer 13

1. Wind
2. Water
3. Explosive
4. Animals

Question 14

Wind seed dispersal + examples (3)

Answer 14

1. By censer mechanism (use of wind - swaying seeds escape out of pores) e.g. Papaver rhoeas
2. Surface area maybe increased byvarious means to allow the seed to be carried long distances by the wind, like the winged seeds e.g. Tilia cordata
3. Some plants use parachutes or silky tufts e.g. Taraxacum officinale

Question 15

Water seed dispersal (3)

Answer 15

1. Relatively rare
2. Cocos nucifera float on ocean currents before being washed up on a beach to germinate
3. Coconut has a fibrous outer layer that help it float

Question 16

Animal seed dispersal + examples (3)

Answer 16

1. Attachment - hooked fruit such as such as burdock (Arctium tomentosum) attached themselves to animals or gardeners
2. Scatter hoarding - nuts such as acorns (Quercus robur), hazelnuts (Corylus avellana) dispersed by rodents
3. Frugivory - Succulent seeds and fruits eaten by birds. Such as hawthorn (Crataegus monogyna) and cherries (Prunus avium)

Question 17

Explosive dispersal + examples

Answer 17

1. Fruit splits open propelling seed into the air e.g Cardamine hirsuta (Hairy bittercress)
2. Tensions setup by unequal drying of the seedcase causes pods of legumes to split along one side e.g. Pisum sativum

Question 18

Main parts of a seed (3)

Answer 18

1. An embryo or immature plant
2. Food store to fuel growth
3. Protective outer coat

Question 19

What is germination?

Answer 19

Is the growth of a plant from its seed to it appearance above ground

Question 20

What is dormancy?

Answer 20

Period of reduced metabolic activity in the plant

Question 21

What is seed viability?

Answer 21

Whether or not the seeed has the capacity to grow - is it live

Question 22

What is quiescence?

Answer 22

Resting period while the seed waits through winter for a suitable growing period

Question 23

Food storage in seeds (2)

Answer 23

1. In cotyledons
2. In endosperm (many monocots)

Question 24

Parts of a dicot seed (9)

Answer 24

1. Embryo 2. Plumule 3. Epicotyl 4. Cotyledon 5. Hypocotyl 6. Radicle 7. Testa 8. Hilum 9. Micropyte

Question 25

What is the testa? (4)

Answer 25

1. The protective seed coat. Waterproof and air tight 2. Very tough and may need to be damaged before germination takes place 3. Formed from integuments surrounding the ovule 4. May contain germination inhibators which enable seeds to stay dormant over winter

Question 26

What is the cotyledon? (2)

Answer 26

1. Seed leaf that provides a store of food for the germinating leaf 2. May be one or two

Question 27

What is the plumule

Answer 27

The part of the seed that will become the first shoot

Question 28

What is the radicle

Answer 28

The part of the seed that will become the first root

Question 29

What is the hilum

Answer 29

The point where the seed was attached within the ovary

Question 30

What is the micropyle? (2)

Answer 30

1. A small hole in the testa where the pollen tube entered the ovule at the time of fertilisation 2. Sometimes water can enter here to trigger germination

Question 31

What is the Hypocotyl (2)

Answer 31

1. Between the cotyledons and root 2. Connects the plumule to the radical

Question 32

What is the epicotyl?

Answer 32

1.Between the plumule and radicle, this lies above the cotyledons and gives rise to the stem.

Question 33

Parts of the embryo (5)

Answer 33

1. Plumule 2. Epicotyl 3. Cotyledon 4. Hypocotyl 5. Radicle

Question 34

What is the Coleoptile? (2)

Answer 34

1. Monocots only 2. Sheath that protects the plumule on its emergence from the soil

Question 35

What is the Coleorhiza (2)

Answer 35

1. Monocots only 2. Sheath like structure that protects the radicle and connects to the coleoptile

Question 36

Dormancy details (4) (Not seeds)

Answer 36

1. Perennial and biennial plants cope with winter cold by slowing down their metabolisms. 2. Growth above ground dies back in herbaceous plants 3. Leaves are shed by deciduous trees and shrubs 4. In evergreens growth slows

Question 37

Process of germination (6)

Answer 37

1. Seed starts to take up water through micropyle (imbibition) 2. Respiration rates rise as cells start to grow and divide 3. Once cells have taken in water the embryo grows by cell division 4. First root develops and radicle is pushed through the seed coat to anchor the seedling as it develops and take in water and minerals from the soil. 5. Next the shoot develops - the plumule emerges from the seed as it splits 6. Plumule develops into whole plant

Question 38

What is epigeal germination? (3)

Answer 38

1. The hypocotyl below the cotyledons grows upward through the soil pulling the cotyledons and plumule to the surface. 2. The cotyledons unfurl as seed leaves. These start photosynthesising and the seeding is independant of its food reserves 3. e.g. French bean *Phaseolus vulgaris*

Question 39

What is hypogeal germination

Answer 39

1. Where the epicotyl above the cotyledones elongates and pulls the plumule to the surface where the first true leaves grow. 2. Cotyledones stay underground and evenntually decompose 3. e.g. Broad bean Vicia faba

Question 39

What is hypogeal germination

Answer 39

1. Where the epicotyl above the cotyledones elongates and pulls the plumule to the surface where the first true leaves grow. 2. Cotyledones stay underground and evenntually decompose 3. e.g. Broad bean *Vicia faba*

Question 40

What does a seed need to germinate? (3)

Answer 40

1. Water 2. Oxygen for respiration 3. A temperature high enough to sustain growth