Leaves

Question 1

What do all leaves originate as? Where?

Answer 1

All leaves originate as primordia, in the buds.

Question 2

What features do most leaves have at maturity?

Answer 2

• stalk (petriole)
• flattened blade (lamina)
• network of veins (vascular bundles)

Question 3

What do flowering plants have at the base? What shape can it have?

Answer 3

axillary bud
- simple (single bladed)
- compound (divided into leaflets)

Question 4

What is the difference between pinnately compound leaves and palmately compound leaves?

Answer 4

Pinnately compound leaves have leaflets in pairs along the rachids.
Palmately compound leaves have all the leaflets attatched at the same point at the end of the petiole.

marihuana is palmately compoud, kocha lubi nie lubi os pinntely compound

Question 5

What are leaves attached to stems with? Where?

Answer 5

Leaves are attatched to stems at nodes, with stem regions called internodes.

Question 6

What is the proper name to describe leaf arrangement?

Answer 6

phyllotaxy

Question 7

What three ways does phyllotaxy occur in?

Answer 7

• alternate
• opposite
• whorled

Question 8

What are the different arrangements of veins in a leaf or leaflet blade?

Answer 8

• pinnate (main midvein within a midrib + secondary veins branch from midvein)
• palmate (several primary veins that fan out from the base of the blade: parallel in monocots, divergent in dicots).

Question 9

Why are leaves green? What does this allow for?

Answer 9

Green leaves capture sunlight and thus go through photosynthesis.

Question 10

Explain the lower surface of leaves.

Answer 10

Lower surfaces of leaves are dotted with stomata:
- CO2 to enter the plant
- O2 and H2O to exit the plant

Question 11

When does transpiration occur?

Answer 11

When water evaporates from the leaf surface.

Question 12

What is guttation?

Answer 12

root pressure forces water out hydathodes (pores at the leaves ends).

Question 13

Explain the outer structure of the leaf.

Answer 13

Epidermis is a single layer of cells covering the entire surface of the leaves.
- upper epidermis has no chloroplasts
- waxy cuticle is often present
- different glands may also be present

Lower epidermis is perforated with:
- multiple stomata
- guard cells (originating from the same parent, containing chloroplasts)
–> FUNCTION: gas exchange and the evaporation of water

Question 14

What regulates the stomata?

Answer 14

• guard cells regulate stomata,
• cell water pressure regulates guard cells

Question 15

Where does most photosynthesis take place? Where is it located? What are the two structures?

Answer 15

MESOPHYLL:
- located in between the two epidermal layers

1) palaside mesophyll: upper laeyer, containing most chloroplasts
2) spongy mesophyll: lower layer

Question 16

What is scattered throughout the mesophyll? What is it composed of?

Answer 16

VEINS (vascular bundles):
- consisting of xylem and phloem
- surrounded by the bundle of sheath

Question 17

What are the different types of specialized leaves?

Answer 17

1) SHADE LEAVES:
- recieve less light
- thinner and have fewer hairs (than the ones exposed to light)
2) LEAVES OF ARID REGIONS (little or no rain)
- thick, leathery leaves
- few stomata
- some have water retaining leaves, or dense hairy coverings
3) TENDRILS
- curl around rigid objects (help climb or support weak stems)
4) SPINES/THORNS/PRICKLES
- reduce water loss
- protect from herbivory
- prickles (outgrowths from the epidermis or cortex)
5) STORAGE LEAVES
- succulents
6) REPRODUCTIVE LEAVES
- new plants at tips
7) FLORAL LEAVES
- bracts
8) INSECT-TRAPPING LEAVES
- venus flytraps

Question 18

What is a leaf?

Answer 18

A lateral outgrowth from the stem whose primary function is the manufacturing of food.

Question 19

What is a twig?

Answer 19

A young woody stem to which most leaves and buds are attached.

Question 20

What is a branch?

Answer 20

A thicker, older, woody stem to which twigs are attached to.

Question 21

What is a trunk?

Answer 21

The main vertical stem of a tree

Question 22

What are deciduous trees?

Answer 22

trees on which all leaves fall at the end of each season of growth

Question 23

What are evergreen trees?

Answer 23

trees on which the leaves remain attached for more than one year.

Question 24

What are the different leaf forms?

Answer 24

conifer: a tree with needle or scale like leaves
broadleaf: a tree with wide, flat leaves

Question 25

Explain the anatomy of broad leaves.

Answer 25

• apex (tip of the leaf)
• margin (outer edge of a leaf blade)
• leaflet (individual blade of a compound leaf)
• midrib (the central or main vein of a leaf)
• rachis (the midrib of a compound leaf)
• blade (lamina: flat part of a leaf)
• petiole (stalk of the leaf)
• axillary bud (lateral bud located at the base of a leaf)
• compound leaf (3+ leaflets attached to a common stalk)
• palmately compound
• linnately compound

Question 26

What are the different types of leaf arrangements?

Answer 26

1) OPPOSITE (leaves occuring in pairs at nodes)
2) ALTERNATE (leaves arranged singularily at intervals along the stems)
3) WHORLED (leaves occuring three or more at a single node)