Stems and secondary growth

Question 1

What are 8 functions of stems?

Answer 1

1. Support photosynthetic and reproductive parts
2. Transport water and nutrients
3. Mechanical support
4. Coordinates chemical responses of the plant
5. Storage
6. Support the roots and transport photosynthates down to them
7. Growth response
8. Position seeds for dispersal

Question 2

What are the 3 ways the vascular tissue can be orientated in the stem?

Answer 2

Continuous cylinder, discrete bundles, scattered

Question 3

In a continuous cylinder vascular bundle:

a) Which way is the phloem
b) which way is the xylem
c) which group of plants
d) secondary growth?

Answer 3

a) Outside
b) inside
c) eudicots
d) yes

Question 4

In discrete vascular bundles:

a) Which way is the phloem
b) which way is the xylem
c) which group of plants
d) secondary growth?

Answer 4

a) outside
b) inside
c) eudicots
d) yes

Question 5

In a scattered vascular bundle:

a) Which way is the phloem
b) which way is the xylem
c) which group of plants
d) secondary growth?

Answer 5

a) outside or in
b) outside or in
Note: one half of the bundle will be xylem, one half phloem, but orientations will be different
c) Monocots
d) no

Question 6

Why is there no secondary growth with monocots?

Answer 6

Secondary growth only happens around individual bundles, which would create pressure points due to the scattered arrangement

Question 7

If they don’t have secondary growth, how can palm trees grow so tall? What does that have to do with their distribution?

Answer 7

Their canopy and stem width is exactly the same size as they were as seedlings. Because they don’t grow wider, they can’t support more leaves. The strategy only lets them grow in tropical environments, since their vasculature will freeze in the winter and will become damaged. Without secondary growth, they can’t replace their vasculature and will die if they freeze

Question 8

What are 6 types of specialized stems?

Answer 8

1. Corms
2. Tendrils
3. Succulents
4. Tubers
5. Rhizomes
6. Stolons

Question 9

What are corms for?

Answer 9

Fleshy underground storage stem

Question 10

What are stolons for?

Answer 10

Found in strawberry plants. Are stems modified for transport to bring the babies away from the mother plant

Question 11

How is the stem modified in succulents?

Answer 11

The leaves are reduced and the stem does the life cycle functions and photosynthesis instead

Question 12

What is primary growth?

Answer 12

Growth that makes a plant taller, through internode elongation and cell division

Question 13

Where does cell division happen in the shoots?

Answer 13

The shoot apical meristem

Question 14

How differentiated are the cells in the apical meristem?

Answer 14

Undifferentiated. The leaf primordium (future leaf tissue) and apical meristem (future stem tissue) arise from the SAM

Question 15

How differentiated are cells slightly below the shoot apical meristem? What can they become?

Answer 15

Only slightly differentiated to become one type of cells. Are the protoderm, procambium, and ground meristem

Question 16

What is indeterminate growth?

Answer 16

The plant keeps growing throughout its life, and keeps producing flowers and fruits until the frost sets in

Question 17

What is determinate growth?

Answer 17

The plant grows until it reaches a certain size, then starts producing flowers and fruits in one go

Question 18

Why do pines and larches grow in clusters?

Answer 18

They’re determinate shoots

Question 19

What type of shoot did flowers evolve from?

Answer 19

Determinate shoot. Plants can cause the end of every shoot to become a flower

Question 20

What are the 2 secondary meristems?

Answer 20

Vascular cambium and cork cambium

Question 21

How is wood produced by trees?

Answer 21

Secondary growth of the vascular cambium

Question 22

What is the vascular cambium?

Answer 22

A layer of cells that separates the xylem and the phloem

Question 23

Where is the secondary xylem located?

Answer 23

In the wood, more towards the outside of the tree

Question 24

Is there a difference between the primary and secondary xylem?

Answer 24

Primary xylem is the innermost layer and is smaller, and the secondary xylem is outside of the primary xylem and is larger

Question 25

Where is the secondary phloem located?

Answer 25

Innermost layer of the bark

Question 26

Is there a difference between the primary and secondary phloem?

Answer 26

Not really

Question 27

Why don’t you find primary phloem in trees that have undergone secondary growth?

Answer 27

It gets squashed by the expanding cells and isn’t functional

Question 28

Why is there a size difference in tree rings?

Answer 28

Trees can undergo more secondary growth in the summer because conditions are better, so rings are larger. In later parts of the season, conditions aren’t as good so the rings are smaller because of less secondary growth

Question 29

What is dendrochronology?

Answer 29

Study of tree growth rings to determine what the conditions were in each year (ie drought, flood, etc)

Question 30

Is the wood of gymnosperms considered “hardwood” or “softwood”? How is it structured?

Answer 30

Softwood. Gymnosperms have no vessel elements, so only the tracheids are there and are very small. There’s a few larger holes scattered here and there to transport resin

Question 31

Is the wood of angiosperms considered “hardwood” or “softwood”? How is it structured?

Answer 31

Hardwood. Angiosperms have vessel elements, and some trees produce really large vessels each spring

Question 32

What does the cork cambium do?

Answer 32

Produces periderms and bark to protect the tree

Question 33

Why does girdling kill a tree?

Answer 33

Cuts the phloem, so the tree can’t transport nutrients