Upload
esme
View
54
Download
0
Embed Size (px)
DESCRIPTION
PLANT PHYSIOLOGY. Plants are dynamic!. Many physiological processes occur in each part of the plant Materials are transported through specialized conducting systems Energy is harnessed from the sun through photosynthesis to forms sugars and other storage products - PowerPoint PPT Presentation
Citation preview
PLANT PHYSIOLOGYPLANT PHYSIOLOGY
Plants are dynamic!Plants are dynamic!
Many physiological processes occur in each part of the plant
Materials are transported through specialized conducting systems
Energy is harnessed from the sun through photosynthesis to forms sugars and other storage products
Stored foods are broken down to yield chemical energy through respiration
Transport of water and mineralsTransport of water and minerals Occurs in the xylem Tracheids and vessel elements -
conducting components Source of water is the soil
surrounding the roots Water moved up through plant to
the leaves often in excess of 300 ft
Water movement in xylemWater movement in xylem Uptake from soil Conduction in the xylem Transpiration in the leaves
Transpiration Transpiration
Transpiration is the loss of water vapor from leaves
Occurs mainly through the stomata (90%)
Driving force behind the movement of water in xylem.
Guard Cells and StomaGuard Cells and Stoma
Guard Cell
Stoma (opening)
Open stomata permit transpirationOpen stomata permit transpiration
Gas exchange can occur freely between the leaf and the atmosphere
Water vapor and oxygen diffuse out of the leaf
Carbon dioxide is able to diffuse into the leaf
TranspirationTranspiration
Large amounts of water vapor are lost by transpiration– 2 liters of water/day for a single corn
plant– 5 liters for a sunflower– 200 liters for a large maple tree – 450 liters for a date palm tree
Transpiration is a major component of the global water cycle
Translocation of sugars in phloem Translocation of sugars in phloem Organic materials
are translocated by the sieve tube members of the phloem
Sieve tube members are living but highly specialized cells End wall
with sieveplate
Phloem translocationPhloem translocation
Moves from source to sink. In late winter, the source may be an
underground storage organ translocating sugars to apical meristems (the sink)
In summer the source is usually photosynthetic leaves sending sugars for storage to sinks such as roots or developing fruits
Phloem translocationPhloem translocation
Sucrose in a watery solution In a growing pumpkin which
reaches a size of 5.5 kg (11 lbs) in 33 days, approximately 8 g of solution are translocated per hour - small pumpkin
Record pumpkin over 1000 lbs
Metabolism Metabolism
Total of all chemical reactions occurring in living organisms
Metabolic reactions that synthesize compounds require an input of energy
Reactions which break down compounds usually release energy
EnergyEnergy All life process are driven by energy A cell or an organism deprived of an
energy source will soon die Among the forms of energy are radiant
(light), thermal (heat), chemical, mechanical (motion), and electrical
One form of energy can be transformed into another form
ATP energy currency of the cell
Cellular Energy TransformationsCellular Energy Transformations
Transfer of electrons (or H atoms) ATP energy currency of all cells
– Cells use ATP when need energy– Cells make ATP when store energy
Other energy molecules – NADP--->NADPH– NAD--->NADH
Photosynthesis Photosynthesis
Transforms the energy of the sun into chemical energy
Is the basis for life on Earth Photosynthetic organisms are at the
base of all food chains Without green plants and algae, life
could not survive
Light absorbing pigments Light absorbing pigments
When light strikes an object it can– pass through the object – be reflected from the surface– be absorbed
For light to be absorbed, pigments must be present
Pigments in plants Pigments in plants Leaf - the major organ of photosynthesis Chloroplasts within the mesophyll cells are
the actual sites of photosynthesis The major photosynthetic pigments are the
green chlorophylls Other pigments: Carotenoids
– Orange - carotenes – Yellow - xanthophylls– Normally masked by the chlorophylls
Granum
Thylakoid
Two stages of photosynthesis both occur in chloroplasts:Light Reactions and Calvin Cycle
Two stages of photosynthesis both occur in chloroplasts:Light Reactions and Calvin Cycle
Thylakoids location of pigments and Light Reaction Granum
Innermembrane
OuterMembrane
Stroma(Calvin Cycle)
Light reactionsLight reactions
Photochemical phase of photosynthesis Radiant energy is absorbed and then
converted into chemical energy Occur extremely rapidly powered by
vast energy of the sun
Results of the Light ReactionsResults of the Light Reactions
Water molecules are split releasing oxygen and electrons
Electrons used in a process that ultimately results in the formation of two energy molecules NADPH and ATP
Calvin Cycle (Dark reactions)Calvin Cycle (Dark reactions)
Biochemical phase of photosynthesis The pathway is named in honor of
Melvin Calvin who received a Nobel Prize in 1961 for his work determining the steps in the pathway
Events of the Calvin CycleEvents of the Calvin Cycle
Transforms CO2 to form sugars Uses ATP and NADPH produced in the
light reactions but doesn’t use light energy directly
The end product of this pathway is the formation of a six-carbon sugar which requires the input of 6 molecules of carbon dioxide
Carbon dioxide for Calvin CycleCarbon dioxide for Calvin Cycle
From the atmosphere Very small fraction (0.035%) of the
Earth's atmosphere Enters the leaf by diffusing through the
stomata
Overall Equation for Photosynthesis Overall Equation for Photosynthesis
CHLOROPHYLLCHLOROPHYLL
6CO6CO22 + 12H + 12H22O O + energy --------> + energy --------> CC66HH1212OO66 + 6O + 6O22 + 6H + 6H22OO
Oxygen release from light reactionOxygen release from light reaction Oxygen released when water is split Diffuses out of the leaves into atmosphere Earth's only constant supply of oxygen No oxygen in early Earth atmosphere Current 20% oxygen atmosphere is the result
of three billion yrs of photosynthesis Living organisms depend on oxygen for
cellular respiration
Products of photosynthesisProducts of photosynthesis Transported to growing fruits, storage
organs, other sinks Sucrose is translocated in the phloem After being unloaded, sugars are usually
converted to starch Very few species store sucrose Only sugarcane and sugar beet are
important sources of sucrose
Sugarcane Sugarcane
Saccharum officinarum is a perenniel member of the grass family
Native to the islands of the South Pacific Grown in India since antiquity Ancient civilizations in the Near East and
Mediterranean countries were acquainted with sugar through Arab trading routes
7th century - grown in Mediterranean
EuropeEurope
Honey remained the principal sweetener until the 15th century
Sugar was an expensive luxury mainly use in medicines to disguise the bitter taste of herbal remedies
Early in the 15th century sugar plantations were established on islands in the eastern Atlantic
Caribbean IslandsCaribbean Islands
Columbus introduced sugarcane on his second voyage in 1493
By 1509 sugarcane was harvested in Santo Domingo and Hispaniola and soon spread to other islands
Many Caribbean Islands were eventually denuded of native forests and planted with sugar cane
Other New World LocationsOther New World Locations
Portuguese started sugar plantations in South America in 1521
Spanish and Portuguese enslaved the native populations to work in the fields
The first sugarcane grown in the continental United States was in the French colony of Louisiana in 1753
Sugar and SlaverySugar and Slavery
Sugarcane was responsible for the establishment of slavery in the Americas
Decimation of the native Indian populations led to the need for workers on the sugar plantations
By the early 16th century, sugar and the slave trade became interdependent initially established in Spanish and Portuguese colonies
Sugar demand increasingSugar demand increasing
Supplies of honey in Europe were decreasing
Growing popularity of coffee, tea, and cocoa in Europe accelerated the demand for sugar
Sugar became the most important commodity traded in the world
Triangle TradeTriangle Trade
First leg - England to West Africa with trinkets, cloths, firearms, salt
Second leg - Africa to Caribbean Islands with slaves
Third leg - Caribbean to England with rum, molasses and sugar
10-20 million African slaves had been brought to the New World
SugarcaneSugarcane
Provides over 50% of the world's sugar supply
Canes are 15 to 20 ft tall with individual stalks up to 6” in diameter
Moist lowland tropics and subtropics Canes generally contain 12 to 15%
sucrose.
Sugarcane Field in Egypt
ProcessingProcessing Canes crushed to extract the sugary juice Juice is concentrated and evaporated to form
a syrup Sugar is crystalized and separated from thick
brown liquid (molasses) Molasses is used in foods, or is fermented to
make rum, ethyl alcohol, or vinegar The crystallized sugar (about 96-97% pure
sucrose) is refined
Sugar beetSugar beet
Beta vulgaris, a member of the Chenopodiaceae is unrelated to sugarcane
Same species as red beets which are native to the Mediterranean region
Provide close to 40% of the world's supply of table sugar
Other Storage Compounds in Plants
Products of photosynthesis are stored as various organic compounds
Starch - most common storage compound– Energy reserve for plants – Energy source for the animals that feed on
the plants Other plants store oils (triglycerides) and
proteins
Summary Plants are dynamic metabolic systems
with hundreds of biochemical reactions Life on Earth is dependent on the flow of
energy from the sun Photosynthesis converts carbon dioxide
and water into sugar using solar energy Various compounds are stored by plants
including sucrose, starch, oils, and proteins