UNIT 5: PLANT LEAVES w/o Phyllotaxy Flashcards
Functions
- Manufacture of food through
photosynthesis - Gas exchange via respiration
- Protect vegetative and floral buds
- Water transport via transpiration - The loss of water vapor through the stomata of leaves.
- Store food during germination
- Horticultural uses
- Food
- Herb
- Compost
- Summer cooling
- Medicinal uses
- Wind, dust, noise reduction
- Aesthetic qualities
- Plant identification
- Beverage
- Propagation from cuttings
- Wildlife habitat
- Aromatic oils and wax
a process occurring in the leaves wherein food is manufactured from water and CO2, with the aid of chlorophyll in the presence of light energy (sunlight or artificial light)
6 CO2 + 12 H2O ——–> C6H12O6 + 6 O2 + 6H2O
light energy glucose
Photosynthesis
Essential factors in photosynthesis –any factor whose presence is required to initiate a reaction
If one of these factors is absent, the reaction will not proceed
- Raw materials – _________
a. _____ through the _____
b. _____ through the _____
substrates
a. CO2 through the stomates
b. H2O through the roots
primarily from the sun but electric light can also be used
- needed to convert simple molecules to more complex ones
energy (light energy)
- Pigments –especially _________
– chloroplast: ______ & ________
- ______: contains chlorophyll (green pigment)
- where light reaction of photosynthesis takes place
- ______: contains enzymes
- where the dark reaction
takes place
- chlorophyll
- grana and stroma
grana
stroma
Optimum temperature
– ___ to ___ degrees Celsius
The rate of photosynthesis is increased as the temperature increases up to 35 degrees (beyond 35 degrees)
5 to 40 degrees celsius
2 steps of Photosynthesis
light reaction
dark reaction
- light dependent reaction
- occurs in the granum of the chloroplasts
light reaction
- light independent reaction
- occurs in the stroma
dark reaction
- Produce sugar from light energy
- Stores energy
- Occurs only in cells with chloroplasts
- Releases oxygen
- Uses water
- Uses carbon dioxide
- Requires light
photosynthesis
- Burns sugars for energy
- Releases energy
- Occurs in most cells
- Uses oxygen
- Produces water
- Produces carbon dioxide
- Occurs in dark and light
respiration
parts of leaves
BLADE
- apex
- margin
- veins
- midrib
- base
petiole
axillary bud
stipule
stem
external structure of leaves
leaf blade
petiole
veins
node
axillary bud
stipule
margin
Wide flattened area of leaf for concentrating sunlight on photosynthetic cells
leaf blade
Short stem that attaches leaf to main stem or branch
petiole
Vascular bundles within leaf for transport
veins
Growth region of stem where leaves or new branches arise
node
Baby leaf or stem
axillary bud
Leaflike outgrowths usually present in pairs at the base of the petiole
stipule
edge of the leaf
margin
For plant identification purposes, the _________, _________, & __________ are key features to note.
Remember, a leaf begins at the _________ or __________.
shape of the leaf margin, leaf tip and leaf base
lateral or auxiliary bud
dicot leaf
- petiole
- veins
- leaf blade
where leaf would be attached to the branch or stem at the node
monocot leaf
- sheath
- ligule
- auricle
- collar
part of leaf that holds leaf to stem –encases stem
sheath
membrane-like tissue extending up from the sheath (on inside) –keeps dirt and moisture out –clear membrane on leaf where attaches to stem
ligule
small appendages that extend out and sometimes around the stem –found at the junction of the blade and sheath –can be clasping or non clasping appendages
auricle
area between the leaf blade and sheath –auricles and ligules are on the inside of this area
collar
- blade-like leaf blade
– wrapped around the stem
– no petiole
– have main vascular bundles running parallel along length of leaf
monocot leaf
- have both a leaf blade and a petiole
– single midrib (Vascular bundles) with branches
dicot leaf
INTERNAL STRUCTURE OF LEAVES
- epidermis
- upper and lower
- stomata - mesophyll
- palisade layer
- spongy layer - veins of vascular bundles
- outermost single layer of the leaf that consists of flattened and transparent cells which permits unobstructed sunlight to enter the underlying photosynthetic cells
- cell walls contain ______ in a continuous layer called ______.
- thin in plants in moist habitats and thicker in dry areas to prevent rapid transpiration
2 types
- cutin
- cuticle
upper and lower epidermis
EPIDERMIS
- has a thicker cuticle because it is the exposed part to the sun
- lesser stomata to prevent rapid transpiration
upper epidermis
- thinner cuticle and contains more stomata
lower epidermis
- contain guard cells to regulate the opening of the stomatal pore
- in darkness, the guard cells are limp and the stomates are closed
- in the presence of light, the guard cells are turgid because they absorb water and the stomates are open
stomata
- Turgidity of the __________ will determine the closing and opening of the cell
guard cells
the middle part of the leaf, rich in chlorophyll, usually surrounded by bundle sheaths and is composed by two distinct tissues:
palisade layer
spongy layer
MESOPHYLL
– the upper layer, vertically elongated and compactly arranged parenchyma cells lying just below the upper epidermis
- ______________: chief photosynthetic cells of the plant
Chlorenchyma cells
PALISADE LAYER
lower layer made up of loosely arranged cells of variable forms
SPONGY LAYER
- branched continuations of the vascular bundles of the petiole and midrib that consists of the xylem and phloem
- in most leaves, the xylem is in the upper part of the veins while the phloem is in the lower part
VEINS OF THE VASCULAR BUNDLES
LEAF TYPES
- conifer
- ginkgo
- dicot
- monocot
The leaves of conifers are needle-like (as on pines) or scale-like (as on junipers (Juniperus)
– Each conifer leaf has a single vein
conifer
unique plant having fan-shaped leaf blades with dichotomous venation in which the veins branch into two equal or unequal lengths.
ginkgo
Most of these blades have pinnate
(feather-like) venation in which major veins diverge from one large mid-vein, with smaller network connections between
dicot
With parallel venation, major veins arise at the base, remain more or less parallel, and converge at the tip with small vein interconnections
monocot
LEAF ATTACHMENT
- petiolate
- sessile
The leaf blade is attached to the stem by a stalk called a petiole
petiolate
When the leaf blade is attached directly to the stem without a petiole
sessile
specialized or modified leaves
- tendrils
- prickles and thorns
- storage leaves/succulent leaves
- reproductive leaves
- insect-trapping leaves
- colorful bracts
- winged petiole
- enlarged petiole
- blade of leaves or leaflets are reduced in size, allows plant to cling to other objects
- sweet pea and garden peas
tendrils
- epidermal outgrowths on stems and leaves
- holly, rose, and raspberries
prickles and thorns
retain water in large vacuoles
storage leaves/succulent leaves
- Kalanchöe plantlets arise on
margins of leaves
reproductive leaves
- pitcher plants, sundews, venus flytraps, and bladderworts
- have modified leaves for
capturing insects - all these plants live under nutrient-poor conditions and digest insect bodies to obtain nitrogen and other essential nutrients
insect-trapping leaves
petal-like leaves
colorful bracts
additional surface area for photosynthesis
- Citrus plants
winged petiole
- petiole is enlarged and filled with air for buoyancy
- Water hyacinth
enlarged petiole
