Leaves Flashcards
(26 cards)
What do all leaves originate as? Where?
All leaves originate as primordia, in the buds.
What features do most leaves have at maturity?
- stalk (petriole)
- flattened blade (lamina)
- network of veins (vascular bundles)
What do flowering plants have at the base? What shape can it have?
axillary bud
- simple (single bladed)
- compound (divided into leaflets)
What is the difference between pinnately compound leaves and palmately compound leaves?
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
What are leaves attached to stems with? Where?
Leaves are attatched to stems at nodes, with stem regions called internodes.
What is the proper name to describe leaf arrangement?
phyllotaxy
What three ways does phyllotaxy occur in?
- alternate
- opposite
- whorled
What are the different arrangements of veins in a leaf or leaflet blade?
- 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).
Why are leaves green? What does this allow for?
Green leaves capture sunlight and thus go through photosynthesis.
Explain the lower surface of leaves.
Lower surfaces of leaves are dotted with stomata:
- CO2 to enter the plant
- O2 and H2O to exit the plant
When does transpiration occur?
When water evaporates from the leaf surface.
What is guttation?
root pressure forces water out hydathodes (pores at the leaves ends).
Explain the outer structure of the leaf.
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
What regulates the stomata?
- guard cells regulate stomata,
- cell water pressure regulates guard cells
Where does most photosynthesis take place? Where is it located? What are the two structures?
MESOPHYLL:
- located in between the two epidermal layers
1) palaside mesophyll: upper laeyer, containing most chloroplasts
2) spongy mesophyll: lower layer
What is scattered throughout the mesophyll? What is it composed of?
VEINS (vascular bundles):
- consisting of xylem and phloem
- surrounded by the bundle of sheath
What are the different types of specialized leaves?
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
What is a leaf?
A lateral outgrowth from the stem whose primary function is the manufacturing of food.
What is a twig?
A young woody stem to which most leaves and buds are attached.
What is a branch?
A thicker, older, woody stem to which twigs are attached to.
What is a trunk?
The main vertical stem of a tree
What are deciduous trees?
trees on which all leaves fall at the end of each season of growth
What are evergreen trees?
trees on which the leaves remain attached for more than one year.
What are the different leaf forms?
conifer: a tree with needle or scale like leaves
broadleaf: a tree with wide, flat leaves
