Ch 35 Stems

Question 1

Three Main Functions of Stems

Answer 1

Growth, supports, and transport

Question 2

Stems produce new tissue throughout plant’s life.

Answer 2

Growth

Question 3

Above-ground structures are held aloft for

light capture, dispersal, etc.

Answer 3

Support

Question 4

Stems connect roots with tips of shoot system.

Answer 4

Transport

Question 5

Undeveloped embryonic shoots

Answer 5

Buds (apical meristems of shoots)

Question 6

Located at tip of stem

Answer 6

Terminal bud

Question 7

Located in leaf axils

Answer 7

Axillary buds (lateral buds)

Question 8

Area on stem where leaf is attached

Answer 8

Node

Question 9

Region of stem between two nodes

Answer 9

Internode

Question 10

Present on herbaceous stems for gas exchange

Answer 10

Stomata

Question 11

Epidermis

Answer 11

Present on herbaceous stems for

protection as with leaves

Question 12

Cover and protect dormant buds

Answer 12

Bud scales

Question 13

Left where bud scales fall off, when bud resumes growth

Answer 13

Bud scale scars

Question 14

Where each leaf was attached to stem

Answer 14

Leaf scar

Question 15

Sites of loosely arranged cells and allows oxygen to diffuse into interior of
woody stem

Answer 15

Lenticels

Question 16

Replacement for epidermis on woody stems

Answer 16

Periderm (outer bark)

Question 17

• Vascular bundles arranged in a circle (in cross section)

* Distinct cortex and pith

Answer 17

Herbaceous Eudicot Stems

Question 18

Function primarily for storage (pith may be mostly open space)

Answer 18

Distinct cortex and pith

Question 19

• Vascular bundles scattered in ground tissue (in cross section)
• No distinct cortex and pith
• Primary growth only (do not produce true wood or bark)

Answer 19

Monocot Stems (All Herbaceous)

Question 20

Production of secondary tissues

Answer 20

Wood, bark

Question 21

– through lateral meristems
– occurs in many “dicots” and gymnosperms
– Vacular Cambium: produces secondary xylem (wood) and secondary phloem (inner bark)
– Cork Cambium: produces periderm

Answer 21

Secondary tissue

Question 22

• outer bark (cork parenchyma and cork)
• Cork cells: replace epidermis in a woody stem
• Cork parenchyma: for storage

Answer 22

Cork Cambium

Question 23

Following dormancy, large xylem cells with thin walls form for increased water uptake

Answer 23

Spring Xylem growth patterns

Question 24

Small xylem cells with thick walls form for greater strength

Answer 24

Summer Xylem growth patterns

Question 25

Crushed each year and is added to the bark

Answer 25

Phloem growth patterns

Question 26

4 Types of wood

Answer 26

Sapwood, Heartwood, Softwood, and Hardwood

Question 27

Functional xylem

Answer 27

Sapwood

Question 28

As trunks increase in girth, the oldest xylem is filled with waste products.

Answer 28

Heartwood

Question 29

Generally refers to the wood of conifers | -wood generally lacking fibers and vessel elements

Answer 29

Softwood

Question 30

Wood of angiosperms; not always literally hard

Answer 30

Hardwood

Question 31

Water and dissolved minerals move from soil through plant body to atmosphere. Water and minerals in plant body move upward, from root to stem to leaf.

Answer 31

Xylem Transport

Question 32

Sugar molecules manufactured in leaves by photosynthesis are transported in throughout plant. Unlike xylem movement is up and down and requires energy from the plant.

Answer 32

Phloem Transport

Question 33

• A measure of tendency for osmosis to occur – i.e. measure of a cell’s ability to release/absorb water – Pure water • W.P. = 0 megapascals (measure of pressure) – Water with dissolved solutes has negative W.P.

Answer 33

Water Potential (W.P.)

Question 34

In Water Potential (W.P.) water moves

Answer 34

– from regions of higher (less negative) W.P. – to regions of lower (more negative) W.P. – Osmosis will occur when W.P.s are unequal.

Question 35

Water moves upward from soil through plant to atmosphere. Some force must explain the movement of water against the pull of gravity. Could involve a push from below or a pull from above. Both occur, but the stronger force in plants is the pull of transpiration.

Answer 35

Xylem transport

Question 36

– evaporative pull causes tension at top of plant – result of W.P. gradient – (ranges from slightly negative in soil and roots to very negative in atmosphere)

Answer 36

Transpiration

Question 37

• Column of water pulled up through the plant remains unbroken – due to cohesive and adhesive properties of water (like in a straw)

Answer 37

Tension–Cohesion Model

Question 38

Even in the tallest plants

Answer 38

Differences in W.P.s are great enough to explain rise of water

Question 39

• Also a pushing force in xylem

Answer 39

Root Pressure

Question 40

In root pressure water moves into roots due to active absorption of mineral ions from soil

Answer 40

– energy used to pump minerals into roots – results in lower ion concentrations in soil – may cause lower W.P. in roots than in soil

Question 41

Root pressure is not strong enough to move water to tops of tall plants

Answer 41

– But when soil is wet, the difference in root and soil W.P. can be great enough to cause guttation.

Question 42

• Dissolved sugar is translocated upward or downward in phloem – from a source of excess sugar (usually a leaf) – to a sink (area of storage or sugar use: roots, apical meristems, fruits, seeds) – slower than xylem transport

Answer 42

Phloem Translocation

Question 43

The predominant sugar translocated in phloem

Answer 43

Sucrose

Question 44

• Explains movement of materials in phloem

Answer 44

Pressure–Flow Hypothesis

Question 45

• Companion cells actively load sugar into sieve tubes at source – requires energy (ATP) – water follows sugar (osmosis) • Companion cells unload sugar from sieve tubes at sink – Water leaves sieve tubes by osmosis • Turgor pressure gradient – produced by water entering phloem at source and water leaving phloem at sink drives flow in phloem

Answer 45

Pressure–Flow Hypothesis

Question 46

5 Special stems

Answer 46

``` Bulb Rhizome Corm Stolon Tuber ```

Question 47

Underground bud with fleshy storage leaves attached to short stem

Answer 47

Bulb

Question 48

Short, erect underground stem covered by papery scales

Answer 48

Corm

Question 49

Horizontal underground stem

Answer 49

Rhizome

Question 50

Horizontal aboveground stem

Answer 50

Stolon

Question 51

Fleshy underground stem enlarged for food storage

Answer 51

Tuber