Seeds And Fruits

Question 1

When does plant growth begin

Answer 1

The seed represents a pause in growth and development

Question 2

Germination

Answer 2

The beginning of growth of a seed to produce a seedling

Question 3

Eudicot seeds

Answer 3

2 cotyledons
Seed coat
Foliage leaves
Epicotyl
Hypocotyl

Question 4

Cotyledon

Answer 4

Often when the seed germinates, or begins to grow, the cotyledon may become the first leaves of the seedling.

Question 5

Hypocotyl

Answer 5

Interphase between the root and the cotyledons

Question 6

Epicotyl

Answer 6

Region above the cotyledons

Question 7

Epigeus

Answer 7

Cotyledons above soil

Question 8

Hypogeus

Answer 8

Cotyledons below the soil

Question 9

Monocot seeds

Answer 9

Pericarp (seed coat)
Endosperm
One cotyledons (scutellum)
Coleorhiza

Question 10

Functions of seeds

Answer 10

Maintain dormancy under unfavourable conditions and postpone development until better conditions arise
Protection to the young plant
Contains stored food
Adapted for dispersal, facilitating the migration of plant genotypes into new habitats
Can withstand low moisture contents of 5% and microbial decay

Question 11

Structure of seeds

Answer 11

Embryo
Energy store- endosperm. Contains the oil or carbohydrate
Protective seed coat or testa

Question 12

Requirements of germination- a seed must be

Answer 12

Oxygen
Water
Be viable
Be free from dormancy
Optimum temperature (about 25-30)
Optimum light levels

Question 13

Process of germination

Answer 13

Uptake of water
Breakdown of carbohydrates by enzymes in respiration
First root- radicle produced
First shoot - plumule produced

Question 14

Quiescence

Answer 14

When seeds are in a state where by they cannot germinate unless the conditions normally required for growth are present

Question 15

Non viable

Answer 15

When seeds are dead or imperfect ie do not contain an embryo

Question 16

Imbibition

Answer 16

When a seed becomes wet it absorbs water irrespectively of whether the seed is dead or alive i.e. a purely physical process termed ‘imbibition’
Some seed coats are impermeable to water, therefore they cannot imbibe and so cannot germinate. This can cause dormancy

Question 17

3 most important requirements for germination

Answer 17

Water
Oxygen
Temperature

Question 18

Types of dormancy

Answer 18

Innate (primary)
Induced (secondary)

Question 19

Why do seeds exhibit dormancy

Answer 19

Ripe seed on the parent is prevented from germinating until it is shed.
Enables the seed to germinate in a favourable season.
Distribute the germination of the progeny over many growing seasons (insurance policy).
Prevent seeds from germinating at too great a depth in the soil.

Question 20

Causes of dormancy

Answer 20

Thick seed coats: stops oxygen or water (some legumes)
Impermeable to oxygen or water at 5ºC (Winter Barley (Hordeum vulgare).
Immature embryos (some orchids).
Germination inhibitors.

Question 21

Dormancy

Answer 21

When seeds don’t germinate even when the environmental requirements for growth are present or conditions are favourable

Question 22

Innate (primary) dormancy

Answer 22

Prevents the embryo from growing when it is still attached to the parent plant (vivipary) and when it is first shed

Question 23

Induced (secondary) dormancy

Answer 23

After a seed has lost its innate dormancy another type can be induced by unfavourable conditions

Question 24

Vivipary

Answer 24

When an embryo germinates when it is still attached to the parent plant

Question 25

Stratification requirement

Answer 25

Ensures that seed will not germinate until favourable conditions

Question 26

Scarification

Answer 26

Seed requires physical damage before it will germinate eg smoke or fire requirement Dormancy in wild oats - the husk restricts oxygen supply to the embryo. Physiological dormancy can be due to immature embryos or the presence of growth inhibitors in the seed.

Question 27

Animal dispersed plants can control

Answer 27

Viability and distribution of seeds Control of retention times in gut Chemical and physical properties of seeds can mediate interaction

Question 28

How is dormancy broken

Answer 28

Stratification requirement Scarification

Question 30

What develops into a seed

Answer 30

Ovule

Question 31

What develops into a fruit

Answer 31

Ovary

Question 32

Parthenocarpic fruits

Answer 32

May develop without seeds Eg bananas

Question 33

Accessory fruits

Answer 33

Include additional flower parts Eg apple and strawberry Pome outercoat derived from the receptacle Core from the carpel. Apples and pears fleshy fruits of the rose family. (endocarp forms a tough membrane)-

Question 34

Simple fruits

Answer 34

Diverse- berries, drupes and pomes Develop from one or several united carpels

Question 35

Succulent

Answer 35

drupe (usually single seeds hard stony endocarp (shell); berry (typically multiple seeds), pomes (highly specialised fleshy fruits).

Question 36

Dry fruit

Answer 36

(achenes): thistles, samaras and cereals (caryopsis).

Question 37

Drupe

Answer 37

Peaches, olives and cherries Single seed with hard stony inner layer

Question 38

Berry

Answer 38

Eg tomatoes, grape Seeds within the fruit Soft fruit walls so seeds have strong seed coats

Question 39

Pome

Answer 39

Pears and apples Endocarp forms a tough membrane Core from the carpel

Question 40

Dehiscent fruits

Answer 40

Pericarp breaks open releasing the seeds

Question 41

Indehiscent fruits

Answer 41

Seed remains in the fruit when shed

Question 42

Purpose of simple fruits

Answer 42

Protecting the developing seed Aid in dispersal

Question 43

Aggregate fruit

Answer 43

Develop from many separate carpels of one flower Eg raspberry, strawberry

Question 44

Types of simple fruit

Answer 44

Succulent Dry (achenes)

Question 46

Multiple fruits

Answer 46

Form from many carpels of many flowers on an inflorescence Eg pineapple

Question 47

Drawbacks of seeds

Answer 47

Large energy sources Match larger than spores

Question 48

Ways in which seeds can be dispersed

Answer 48

Wind - airborne or rolled Animals Water Man (seed trade) Self propelled dispersal

Question 49

Structural adaptations to aid dispersal

Answer 49

Weight Size Digestibility Hooks Air spaces

Question 50

Mechanical seed dispersal

Answer 50

Indian balsam (Impatiens glandulifera) and orange jewelweed (Impatiens capensis) ballistically disperse their seeds- explosive dehiscence

Question 51

Animal dispersal

Answer 51

Mammals Often green fruits: pears, apples Aromatic scents, sweet pericarp Attract ants which carry seeds away but don’t eat them all the larvae Hooked fruits and seeds-10% of angiosperms Hooked mericarps Cleavers

Question 52

Broom

Answer 52

Broom As pod matures and dries, two pod halves split and wrap in alternate directions, audibly snapping apart and catapulting the seeds. Around mean of 2.3m away from plant

Question 53

Wind dispersal

Answer 53

very small seeds blown large distances by the wind, e.g. Digitalis purpurea. Seeds under a milligram use aerodynamic drag to slow their descent Larger seeds have adaptations which increase their surface area – hairs on willows or complex parachutes dandelion Samaras with rotating wings stabilise flight suiting windy conditions but in the rainforrest they fall vertically in calm conditions Alsomitra macrocarpa flying wing 15cm glide for many hundreds of metres on convection currents.