Chapter 6 Flashcards
What’s the main function of leaves?
Manufacturing food Exchange gasses Transpiration Evaporation Store food
Why does plants manufacture of food?
help the plant to produce food
converting the energy in sunlight into chemical energy
plant can make glucose during photosynthesis.
How does the plant exchange gases?
Openings, stomata, helps exchange gasses.
Day - CO2 in, O2 out
Night - O2 in, CO2 out
What is the purpose of transpiration and evaporation?
Helps pull water from roots.
Help cooling the plant
How do leaves store food?
In form of starch
Of what dat the basic dicotyledonous leaf consist?
Leaf base Two stipules Petiole auxiliary bud Leaf blade
Leaf base?
Expanded area of petiole where leaf attaches to stem.
Paired stipules?
Located each side of leaf base.
Two small flaps protect young blade as develops.
Petiole?
Stalk connects blade to leaf base
Inside tiny vessels, connected with veins in leaf
Blade?
Major photosynthetic surface of plant, appears green.
Veins?
Visible in leaf blade are vascular bundles for transport of organic molecules and inorganic substances.
What are organic molecules?
Sucrose
Amino acids
What are inorganic substances?
Water
Mineral ions
Auxiliary bud?
Develops in axil between petiole and stem.
Potential to form shoots or flowers.
What is a simple leaf?
When only single blade inserted directly on petiole.
What is a compound leaf?
Blade two or more subunits: leaflets
What are the different layers of the leaf?
Upper epidermis
Lower epidermis
Mesophyll
Vascular bundles
Upper epidermis?
Layer transparent cells-cover up surface of leaf
Allows light to pass through mesophyll cells
Protect inner cells
Produce cuticle
What is the cuticle?
Waxy layer - cover upper epidermis
Lower epidermis?
Layer Transparent cells - cover lower surface leaf Reduces water evaporation Allow light pass through mesophyll cells Protect inner cells Sometimes produce cuticle Stomata
Stomata?
Between epidermal cells Guard cells on each side Control opening and closing Gaseous exchange CO2 and O2 diffuse in and out Transpiration Few chloroplasts some photosynthesis
Mesophyll?
Between two epidermises
Top - palisade: most photosynthesis takes place
Bottom - spongy m: round, loosely arranged; air spaces between for gaseous exchange by diffusion between m cells and air.
Photosynthesis also takes place
Vascular bundles?
Xylem
Phloem
Xylem?
Tiny tubes - xylem vessels
Transport inorganic substances
Phloem?
Transport inorganic substances.
(Translocation
Why is Geranium a well known plant in Namibia?
Grow throughout Namibia
Gardeners like to plant in pots
Easy to get from nurseries
Why is Elodea common?
Aquatic plant/waterweed
Use in aquariums for O2 for fish
Easy to get from fish shops
What is the definition of photosynthesis?
Method of nutrition in green plants by trapping light energy in chlorophyll and producing organic substances (carbohydrates - glucose), using water, carbon dioxide with release of O2 as byproduct.
What is the word equation for photosynthesis?
Carbon dioxide + water + (chlorophyll;light energy) =>glucose + oxygen
How is the leaf adapted to carry out photosynthesis?
- leaf supported by petiole expose largest possible are to sunlight/air
- leaf large surface area exposed to sunlight and air. Absorb max sunlight
- thin allow light penetrate all cells. Diffusion quicker, reduced distance
- upper - lower epidermis transparent; allow light through to mesophyll layer.
- palisade m cells closely packed absorb more incident light
- palisade m cells near leaf surface maximize light interception
- pmc arranged at right angles, reduce number of cell walls for light to pass through
- pmc large amounts of chloroplasts maximise sunlight absorption
- smc round, loosely packes; accommodate air spaces-act as reservoirs for gasses and assist in gaseous in gaseous axchange
- mesophyll cells large vacuoles middle; push chloroplasts to edge of cells
- mesophyll cell walls thin cell walls; short diffusion pathway
- chloroplasts contain chlorophyll: trap sunlight energy used to combine CO2 and H2O to make glucose
- chloroplasts move in mesophyll cells towards light
- chloroplasts move in mesophyll cells away from high intensity avoid damage
- Xylem: present within short distances form every mesophyll cell fot transport of water to cells, some of which will be used in chloroplasts for photosynthesis.
- Phloem:present in short distances from every mesophyll cell, to translocate products of photosynthesis
What is the process of photosynthesis?
- Light energy absorbed in chloroplasts, trapped by chlorophyll in chloroplasts of mesophyll cells
- Light energy transformed to chemical energy
- Water absorbed from soil by root hair cells - osmosis
- Water from in root hair cells through cortex and endodermis into Xylem to leaves
- From leaf Xylem, water by osmosis into mesophyll cells and chloroplasts
- Chemical energy used to split water molecules hydrogen ions and oxygen
- Oxygen released by diffusion into air spaces of leaf; then through stomata out
- Carbon dioxide enters diffusion stomata, diffuses into air spaces
- diffuses into chloroplasts of mesophyll cells
- Carbon dioxide hydrogen atoms combined
Carbon dioxides converts into carbohydrates, using sunlight energy - Forms energy rich carbohydrate molecule - glucose
Importance of photosynthesis?
- Photosynthesis sugar, oxygen. Oxygen important to survive
- Need energy grow;reproduce. Respiration to produce ATP, used for energy. Respiration reaction uses glucose
- Glucose used to build plant cell structures; cellulose walls
- Glucose changes to insoluble starch, fats, oils, proteins; stored in seeds leaves roots.
- Photosynthesis reduce CO2.
Can reduce global warming
Shade leaves?
Thinner, larger more surface area, more chlorophyll.
More efficient in harvesting sunlight at low light levels
Sun leaves?
Thicker, smaller less surface area, less chlorophyll
Develop longer palisade or an additional layer of palisade
Why is gaseous exchange important?
Photosynthesis: need CO2, means disposing of O2.
Respiration: need O2, means disposing CO2
Water vapor for osmosis
How is stomata adapted for sufficient gaseous exchange?
Optimum size, shape distribution for efficient diffusion
Surrounded by 2 guard cells, attached at each end of both cells
Stomata open, spongy palisade mesophyll in continuous contact with outside atmosphere.
Carbon dioxide enter by diffusion
Water in mesophyll cells across cellular membranes, evaporates into air spaces, and evaporates through stomata.
Oxygen exactly the same: mesophyll cells>cellular membrane>air spaces>stomata
How have leaves adapted for efficient gaseous exchange?
Thin, stomata, large surface area
