Upload
amie-barker
View
213
Download
0
Tags:
Embed Size (px)
Citation preview
Plant Nutrition and Plant Nutrition and PhotosynthesisPhotosynthesis
Reading QuizReading Quiz•Get out a small sheet of paper and write your name at Get out a small sheet of paper and write your name at
the top. Answer the following questions the top. Answer the following questions in silencein silence
1)1)What is the chemical process that plants use to make What is the chemical process that plants use to make
energy from sunlight?energy from sunlight?
2) What reactants do plants need to do this reaction?2) What reactants do plants need to do this reaction?
3) Why are plants green?3) Why are plants green?
4)What is the organelle that absorbs sunlight?4)What is the organelle that absorbs sunlight?
6CO2+6H2O+sunlightC6H12O6+6O2
CO2, H2O, and sunlight
Only color they don’t absorb well
Chloroplasts
ATP: The Energy unit of the Cell
ATP (adenosine triphosphate,三磷酸腺苷)
O O O O CH2
H
OH OH
H
N
H H
O
NC
HC
N CC
N
NH2Adenine
RibosePhosphate groups
O
O O
O
O
O
-
- - -
CH
Cell Energy use in Active Transport
• Energy is released from ATP (-30.54 kJ/mol)– When the 3rd phosphate bond is broken
Trapping Energy from Sunlight
• The process that uses the sun’s energy to make simple sugars is called photosynthesis
• Bases of all ecosystems on Earth
6 CO2 + 6 H2O + Light energy C6H12O6 + 6 O2
Tissue of a LeafTissue of a Leaf•Plant tissue:Plant tissue:
•Upper epidermisUpper epidermis water proof outer water proof outer
covering; covered with covering; covered with cuticlecuticle
•Palisade mesophyllPalisade mesophyll photosynthetic cells; photosynthetic cells;
lots of chloroplastslots of chloroplasts
•Spongy mesophyllSpongy mesophyll space for CO space for CO22/O/O22
circulationcirculation
•PhloemPhloem transport solutes transport solutes
•XylemXylem transport water and salts transport water and salts
•Lower epidermisLower epidermis stomata for gas stomata for gas
exchangeexchange
Vein
Leaf cross section
Mesophyll
CO2 O2
Stomata
Where Does CO2 come from?•Enters leafs through the stomata
Where does H2O come from?•Absorbed by roots and pulled up to the leaves by cohesion and adhesion
(transpiration)
The Problem with Gas Exchange• How does CO2 and O2
get in and out of a plant?– Stromata under the
leaves• What else can escape
through a stromata that the plant needs?– H2O
• What problems must plants in dry, hot climates deal with?– The plant needs to
take in CO2 and release O2, but the open stromata will also release H2O
H2O out
Where does Light Energy come from?
• Energy from the sun must be absorbed by pigments, light absorbing molecules (chlorophyll)
• Inside a chloroplasts are thylakoids and inside their membranes are pigments
• What wavelength of light do the pigments not absorb?– Green; reason why plants
are green
Photosynthesis: 2 Reaction Set
1) Light-dependent reactions chemical reactions driven by light energy absorbed by pigments
2) Light-independent reactions chemical reactions that use ATP and NADPH to create sugars out of CO2
H2O CO2
Light
LIGHT REACTIONSCALVINCYCLE
Chloroplast
[CH2O](sugar)
NADPH
NADP
ADP
+ P
O2
ATP
The Light-Dependent reactions
LightReflectedLight
Chloroplast
Absorbedlight
Granum
Transmittedlight
Pigments- light absorbing moleculesChlorophyll main light absorbing pigment
Light-dependent reactions use chlorophyll to trap light energy. This energy produces ATP, NADPH, and O2
The Light-Dependent reactions
Photolysis
H2O CO2
Light
LIGHT REACTIONSCALVINCYCLE
Chloroplast
[CH2O](sugar)
NADPH
NADP
ADP
+ P
O2
ATP
The Light-Independent reactions
Final NumbersUse Produce
Light-Dependent Reactions
Sunlight NADPH
H2O ATP
O2
Use Produce
Light-Independent Reactions
(Calvin Cycle)
NADPH
RuBP
RuBP (recycled to keep
cycle going)
ATP PGAL (Which form sugars)
CO2
Photosynthetic RatesPhotosynthetic Rates
Structure of a Leaf• If photosynthesis occurs
mostly in the leaf, what factors must be considered when designing a leaf?
1)Amount of sun exposure– More surface area = more
photosynthesis
2)Movement of CO2 and O2– Space for exchange
3)Movement of H2O and products of photosynthesis– Water from the roots and
organic molecules to other areas
Photosynthetic Rates: Light• What factors could affect
photosynthetic rate?– Light intensity– Amount of CO2 / H2O– Too much O2 – Temperature
• Increase Light Intensity = Higher Photosynthetic rate
– BUT there is a max. limit; Why?
• Limit to how fast enzymes can work
Photosynthetic Rates: Temperature• If just temperature is increased,
rates go up Why?– More kinetic energy = faster
enzymatic rates
• Why is there only a small increase in rate?
– Light-dependent stage is limited by light intensity
• What would be create the best photosynthetic rate?
– High temperature and high light intensity
• Why do rates drop after raising the temperature too high?
– Enzymes (proteins) denature
Photosynthetic Rates: Limiting Factors• Even with high temps
and high light intensity, what factors must be considered?
– Availability of CO2 and H2O
– Too much O2 (limits enzymes in high conc.)
• Limiting factor the factor least available or having the strongest affect on reactions rates
– Can be light, temperature, CO2, H2O, or O2 depending on the situation
Limiting Factors Practice• What is the limiting factor for :1) Plants in the rain forest?
– Light intensity; Rain forests have plenty of rainfall and humidity but limited space; plants fight for sunlight
2) Plants in the deserts?– Water; Deserts have plenty of sun and
open space but very little rain3) Plants underwater?
– CO2/Sunlight; Dissolved CO2 harder to access and sunlight loses strength as it passes through water
4) Plants in the arctic?– Temp/Sunlight; Cold temperatures
and little direct sunlight limits growth
Limiting Factors on Growth• We have plant that gets
plenty of sunlight, water, and CO2. However it seems to grow very slowly and looks unhealthy. Why?
– Missing other nutrients– Soil does not contain enough
mineral salts
• Mineral salt plant nutrients needed for growth and repair
– Nitrates– Phosphates– Ions like Mg and K
Mineral Salts• Nitrates nitrogen based
compounds like NH3, NO2-, and
NO3- which are used to build
amino acids– Most nitrogen is N2 which is
unusable– Nitrogen fixation by bacteria
make nitrates – Animal urine has urea which is
similar to NH3
• Phosphates PO43- which is
used to build DNA and RNA• Magnesium ions Mg2+ which
is used to build chlorophyll• Potassium ions K+ which is
used to make stable cells all over the plant
Getting Mineral Salts• Mineral salts must be present in
the soil for plants to grow. How can we add mineral salts?
1) NPK fertilizers mix of material containing NPK ions which are absorbed by the roots
– Can wash away and cause algae blooms rapid growth of algae in lakes that causes the ecosystem to crash
2) Humus natural decomposition of material (compost) that slowly added mineral salts to soil
– Farms can never be sure if enough of each Ion is present in compost