Basic systems of plants

Question 1

What are the two basic systems of angiosperms?

Answer 1

Root system, shoot system

Question 2

What comprises the shoot system?

Answer 2

Stems, leaves, flowers

Question 3

Define: lamina

Answer 3

Leaf blade

Question 4

Define: petiole

Answer 4

Leaf stalk

Question 5

Define: midrib

Answer 5

Middle vein in a leaf

Question 6

Define: leaf

Answer 6

A lateral appendage on the stem, in the axil of which there is an axillary bud

Question 7

Define: axillary bud

Answer 7

• Bud in the axil of a leaf
• Meristematic region
• Can grow the shoot through branching
• Damage to apical bud stimulates axillary bud to take over

Question 8

Define: palmately compound

Answer 8

Leaflets diverge from the tip of the petiole

Question 9

Define: pinnately compound

Answer 9

Leaflets arise either side of an axis / rachis

Question 10

Define: rachis

Answer 10

Central axis of a compound leaf or inflorescence

Question 11

Define: petiolule

Answer 11

Connects leaflet to rachis

Question 12

What controls leaf orientation and why?

Answer 12

Petiole controls leaf orientation, usually for maximum sunlight.

Sometimes not for maximum sunlight e.g. Eucalyptus leaves drooping vertically so they are not exposed to the harsh midday sun.

Question 13

Leaves can change type between stages:

Answer 13

Juvenile, intermediate, adult

Question 14

Define: primary root

Answer 14

First root

Question 15

Define: root cap

Answer 15

Protects root meristem, expendable cells

Question 16

Define: shoot apical meristem

Answer 16

• Meristematic region in the shoot, at the apical bud
• Contains many tightly packed undifferentiated cells undergoing rapid mitosis
• Grows upwards, creating nodes and internodes

Question 17

Define: root apical meristem

Answer 17

• Meristematic region in the root
• Contains many tightly packed undifferentiated cells undergoing rapid mitosis
• Grows downwards, creating root cap cells below and other root tissue above

Question 18

What are the functions of the root system?

Answer 18

• Absorbing water and nutrients
• Support

Question 19

What are two growth characteristics of roots?

Answer 19

• Positively gravitrophic: grow downwards whichever orientation they land at
• Circumnutation: root swirls around as it grows, allowing it to dodge obstacles and not get stuck

Question 20

Define: apical bud

Answer 20

• Bud at the apex of the plant,
• Contains shoot apical meristem
• Main place of shoot growth unless damaged, which causes axillary buds to take over

Question 21

Define: adventitious roots

Answer 21

Roots originating from anywhere other than the radicle.

Question 22

Define: root hairs

Answer 22

Epidermal extensions to increase surface area of roots, made by an epidermal cell extending outwards. Can account for up to 70/80% of root absorption.

Question 23

Define: root nodules

Answer 23

Symbiotic relationship with nitrogen fixing bacteria. Bacteria infect a region, fix nitrogen into a form usable by the plant, take sugar from the plant.

Question 24

Define: stolons

Answer 24

• Runners / horizontal above ground stems e.g. strawberries
• Contain nodes / internodes, nodes can sprout leaves, this allows asexual reproduction

Question 25

Define: rhizomes

Answer 25

- Underground stem - Contains nodes and internodes - Scaly, paper-like leaves

Question 26

Define: bulbs

Answer 26

- Underground, short stem e.g. onion - Have fleshy layers that are actually leaves (not photosynthetic) - For storage

Question 27

Define: corms

Answer 27

- Underground, compressed, swollen stem - Appear similar to bulbs although do not have layers of leaves

Question 28

Define: tubers

Answer 28

- Enlarged ends of rhizomes, fleshy underground stems for storage e.g. potatoes - Eyes of a potato are actually axillary buds marking nodes, sprouts are the stem branching - Some root modifications are also called tubers

Question 29

Define: fruiting spurs

Answer 29

- Stem modification bearing fruit rather than leaves

Question 30

Define: fleshy stems

Answer 30

- Stem modification e.g. saltmarsh plants

Question 31

Define: thorns

Answer 31

- Stem modification, spiky structure borne from an axil e.g. prickly box

Question 32

Define: tendril

Answer 32

- Threadlike modification in climbing plants, can be either a modified stem or leaf

Question 33

Define: spines

Answer 33

- Leaf modification, spiky structure similar to thorn/prickle

Question 34

Define: phyllode

Answer 34

- Leaf modification, resemble and take on role of a normal leaf but actually are expanded petioles e.g. Acacia melanoxylon

Question 35

Define: cladode

Answer 35

- Stem modification, resemble and take on the role of a leaf but are actually photosynthetic stems e.g. Allocasuarina sp. - Segments are nodes, nodes sprout reduced scale leaves

Question 36

Define: phylloclade / cladophyll

Answer 36

- Stem modification, flattened stems that resemble and take on the role of a leaf but are actually photosynthetic stems e.g. celery top pine, epiphyllum

Question 37

Define: prop / stilt roots

Answer 37

Aerial roots for support, as seen in corn, banyan, pandani

Question 38

Define: buttress roots

Answer 38

Aerial roots seen in many tropical plants, for support when roots are shallow due to an abundance of water.

Question 39

Define: air roots / pneumatophores

Answer 39

Roots found in mangroves, that grow upwards to provide oxygen intake in swampy, poorly drained habitats