Nutrients from soil and air 5% of a plant’s dry weight is organic (built mainly from CO 2 ) - plant’s are predominantly built from the air C. Sugar Chapters 32: Plant Nutrition and Transport Fig. 32.1A - carbon and oxygen from CO 2 - hydrogen from water - Two fates - cellular respiration or biosynthesis lants need to make everything (organic) from scratch (inorgan (Some)
Chapters 32: Plant Nutrition and Transport. I. Nutrients from soil and air. A. Plants need to make everything (organic) from scratch (inorganic). B. 95% of a plant’s dry weight is organic (built mainly from CO 2 ). - plant’s are predominantly built from the air. C. Sugar. - PowerPoint PPT Presentation
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I. Nutrients from soil and air
B. 95% of a plant’s dry weight is organic (built mainly from CO2)
- plant’s are predominantly built from the air
C. Sugar
Chapters 32: Plant Nutrition and Transport
Fig. 32.1A
- carbon and oxygen from CO2 - hydrogen from water- Two fates
- cellular respiration or biosynthesis
A. Plants need to make everything (organic) from scratch (inorganic)
(Some)
I. Nutrients from soil and air
Chapters 32: Plant Nutrition and Transport
Fig. 32.1A
D. Nitrogen, phosphorus, Mg++, etc… from soil
- used in combination with glucose to make hormones, ATP, coenzymes (chlorophyll), nucleotides, amino acids, etc…
i. nitrogen
ii. Magnesium (Mg++)- part of chlorophyll
iii. phosphorus- ATP, nucleic acids, phospholipids, etc…
(Some)
II. PM of roots control solute uptake
Chapters 32: Plant Nutrition and Transport
A. Root hairs provide high surface area
- Casparian strip
Fig. 32.2
- Intracellular route vs. Extracellular route
C. Epidermis --> cortex --> endodermis --> xylem
- waxy belt through walls of endoderm- stops solution from entering xylem via cell walls
D. Endodermal membrane is highly selective (gatekeeper -> can’t get into xylem without being aloud through)
B. Must be dissolved in solution to enter
III. Getting xylem sap up to the shoot system
Chapters 32: Plant Nutrition and Transport
A. Water/minerals (xylem sap) must somehow get up xylem vessel
B. How does it do this against gravity???
- minor push from roots actively pumping ions into xylem (water follows by osmosis)
i. Root pressure
- works over a few meters- not enough for taller trees, and many trees (i.e. giant sequoia) produce NO root pressure
III. Getting xylem sap up to the shoot system
Chapters 32: Plant Nutrition and Transport
A. Water/minerals (xylem sap) must somehow get up xylem vessel
B. How does it do this against gravity???
Fig. 32.3
ii. Transpiration- loss of water from leaves (stomata) pull xylem sap upward
a. cohesion (water hydrogen-bonding to other waters): makes the xylem sap like a continuous string
b. Adhesion (water sticking to other molecules): sticks to cellulose walls of xylem
- Two properties of water that make this possible:
III. Getting xylem sap up to the shoot system
Chapters 32: Plant Nutrition and Transport
A. Water/minerals (xylem sap) must somehow get up xylem vessel
B. How does it do this against gravity???
Fig. 32.3
ii. Transpiration- water molecule at end of chain in leaf is heated by solar energy
- This molecule diffuses out of the stomata and evaporates
- As it does this, it pulls on the neighboring waters (cohesion), the neighbors pull on their neighbors and so on all the way to the roots
(Without the suns KE, the water in the leaf would remain stuck to its neighbors - no pulling force, no transpiration)
III. Getting xylem sap up to the shoot system
Chapters 32: Plant Nutrition and Transport
A. Water/minerals (xylem sap) must somehow get up xylem vessel
B. How does it do this against gravity???
Fig. 32.3
ii. Transpiration- What about adhesion?
- adhesion counters downward pull of gravity by “grabbing” walls of xylem
- holds water in xylem when transpiration is not occurring (at night)
IV. Guard cells control transpiration
Chapters 32: Plant Nutrition and Transport
A. Transpiration works for and against plants
i. Water loss
- plant needs to lose water in order to get minerals
- average maple tree loses 200L per hour during summer
- not a problem only if there is enough water in soil
A wilting plant caused by water loss under dry conditions
IV. Guard cells control transpiration
Chapters 32: Plant Nutrition and Transport
B Stomata
i. Each has a pair of guard cells
- change shape to control opening- open during day when photosynthesis rates are high (need CO2)
- closed at night to save water
Guard cells of stomata
IV. Guard cells control transpiration
Chapters 32: Plant Nutrition and Transport
B Stomata
ii. How do guard cells change shape to regulate open/closed state?
Fig. 32.4
1. opening stomata- guard cells ACTIVELY take up K+
- water follows by osmosis- causes swelling and high turgor pressure (pressure of cells contents against cell wall)
- causes cells to bend away from each other due to arrangement of cellulose fibers:
IV. Guard cells control transpiration
Chapters 32: Plant Nutrition and Transport
B Stomata
ii. How do guard cells change shape to regulate open/closed state?
Fig. 32.4
1. opening stomata- What stimulates guard cells to take up K+?
a. sunlight, low CO2, circadian rhythm (biological clock)
IV. Guard cells control transpiration
Chapters 32: Plant Nutrition and Transport
B Stomata
ii. How do guard cells change shape to regulate open/closed state?
Fig. 32.4
2. Closed stomata- actively pump out K+- water follows passively (osmosis)- cells sag and stomata close:
IV. Guard cells control transpiration
Chapters 32: Plant Nutrition and Transport
B Stomata
ii. How do guard cells change shape to regulate open/closed state?
Fig. 32.4
2. Closed stomata
- stimulation to pump out K+
a. Too much water loss during day- result in decline of CO2 uptake (sugar production declines), which is why crop yields decline in droughts
3. Opening and closing balanced b/w need to save water and need to make sugar
V. Phloem transport (sugar/organic compounds)
Chapters 32: Plant Nutrition and Transport
A. Phloem sap
i. Sugary solution moving through seive-tube members
ii. Main solute = sucrose
iii. Hormones, inorganic ions, amino acids
iv. Moves in ALL directions
v. All phloems have a source and sink
- sugar source: where sugar is made (in leaves by photosynthesis or generated by breaking down from starch)
- sugar sink: where sugar is consumed or stored (growing roots, shoot tips, fruits, non-photosynthetic stems, etc…)
-storage sites can be both sources and sinks depending on environment (tubers, taproots, bulbs, etc…)
a. sinks during summer (maximum photosynthetic activity)b. source during spring (growth)
V. Phloem transport (sugar/organic compounds)
Chapters 32: Plant Nutrition and Transport
A. Phloem sap
vi. How does phloem sap move from source to sink?
- pressure-flow mechanisma. Sugar enters phloem at source by active transport
Fig. 32.5
b. Water follows by osmosis
- makes water pressure high at source
c. Sugar actively transported out of phloem at sink
d. Water follows by osmosis- water pressure low at sink
e. Hydrostatic pressure gradient causes water to flow from source to sink NO MATTER WHERE THEY ARE LOCATED (sugar goes along for the ride)
V. Phloem transport (sugar/organic compounds)
Chapters 32: Plant Nutrition and Transport
A. Phloem sap
vii. How can one test the pressure-flow mechanism?
i. Using Aphids
Fig. 32.5
a. Aphids feed by inserting their stylus into phloem of plantb. Releases honeydew (phloem sap minus nutrients absorbed by aphid) from anusc. Sever aphid from styletd. Closer stylet to source, quicker it drips:
VI. The essential nutrient of plants
Chapters 32: Plant Nutrition and Transport
A. Hydroponics
i. Can be used to determine essential nutrients
ii. Grow plants in a solution (NO soil) of minerals with known concentration
Fig. 32.6
iii. Air bubbled into solution so roots get enough oxygen for cellular respiration
iv. Remove minerals(s) or change concentration of mineral(s) and compare to control plant
VII. Essential nutrients of plants
Chapters 32: Plant Nutrition and Transport
A. macronutrients
i. 9 out of 17
ii. Need in large (macro) amounts
iv. Ca, K, Mg
iii. C, N, O, H, S, P (The big six of course)
- Calcium (Ca++) - formation of cell walls, combines with proteins to form “glue” of middle lamina, regulate selective permeability
- Potassium (K+) - cofactor (non-protein chemical compound bound to an enzyme and required for catalysis) of many enzymes, opening and closing stomata (main solute for osmotic regulation)
- Magnesium (Mg++) - component of chlorophyll, cofactor of many enzymes
VII. Essential nutrients of plants
Chapters 32: Plant Nutrition and Transport
B. micronutrients
i. The other 8
ii. Need in small (micro) amounts
iii. Fe, Cl, Cu, Mn, Zn, Mo, B, Ni
- cofactors of enzymes
a. ex. Fe (iron) is a cofactor of many ETC proteins as it accepts and donates electrons
a. ex. There is one molybdenum (Mo) for every 16,000,000 hydrogens
- Recycled over and over again (need very little)
VIII. Quality of nutrients in soil determines quality of your own nutrition
Chapters 32: Plant Nutrition and Transport
Corn growth in nitrogen rich (left) vs. nitrogen poor (right) soil
Fig. 32.6
IX. Root hairs take up cations using cation exchange
Chapters 32: Plant Nutrition and Transport
A. Cation
i. Positively charged ion (K+, Mg++, Ca++)
B. Clay tends to me negatively charges
C. Cations stick to clay
- keeps them from draining away
D. Roots secrete H+ (acid) in exchange for another cation
- this is why acid rain is not good for soil, it strips away the cation nutrients
E. Anions are easier for roots to absorb (NO3-
(nitrate) vs. NH4+ (ammonium)
- anions drain out of soil easily- unfertile soil, eutrophication
Fig. 32.8
X. Parasitic plants
Chapters 32: Plant Nutrition and Transport
A. Dodder
i. yellow-orange threads
ii. No photosynthesis
B. mistletoe
i. CAN do photosynthesis
Both dodder and mistletoe may kill host by blocking too much light or taking too much food
iii. Gets organic nutrients from other plants
iv. Uses specialized root to tap into vascular tissue
ii. Supplements diet by siphoning sap from vascular tissue of host
Fig. 32.12
Dodder
Mistletoe
XI. Carnivorous plants
Chapters 32: Plant Nutrition and Transport
A. Sundew and venus flytrap
i. Get nitrogen by digesting flies
ii. Sundew uses sticky sugar substance to attract and trap insects
iv. Both secrete digestive enzymes onto their prey
iii. Venus flytrap has touch sensory hairs that close when touched twice in a row
XII. Most plants depend on bacteria to supply nitrogen
Chapters 32: Plant Nutrition and Transport
A. Recall the nitrogen cycle
i. Plants can’t use N2 (N N)
ii. Nitrogen cycle:
Fig. 32.12
Fig. 36.16
iii. Ammonium is a cation (gets stuck to clay and therefore hard to absorb)
iv. Plants prefer Nitrates (anion)
XII. Most plants depend on bacteria to supply nitrogen
Chapters 32: Plant Nutrition and Transport
A. Recall the nitrogen cycle
v. Plants will convert nitrates back to ammonium for amino acid biosynthesis
Fig. 32.13
XIII. Legumes house nitrogen-fixing bacteria
Chapters 32: Plant Nutrition and Transport
A. Legumes (plants that produce pods)
i. Have nodules on roots filled with Rhizobium
Fig. 32.14
ii. Rhizobium
- genus of most nitrogen-fixing bacteria in roots of legumes
- convert N2 directly to ammonium, which can be used by plant directly (it’s already inside)- excess leaks into soil making it more fertile
a. This is why farmers tend to rotate their crops: one year legume, one year non-legume
iii. Plants give organic molecules to Rhizobium (mutualistic)
XIV. Genetic engineering plants
Chapters 32: Plant Nutrition and Transport
A. Gene gun
i. Used to “shoot” foreign genes into plant cell (or animal cell)
ii. DNA integrates into genome
iii. Cells now make new protein
Fig. 32.16
XIV. Genetic engineering plants
Chapters 32: Plant Nutrition and Transport
A. Gene gun
iv. Many new organisms have been made this way:- virus resistant cotton plants
- potato plants that produce their own insecticide- slow spoil tomatoes
- Can we get plants to synthesize medicine? Make grain with all eight essential amino acids? Put genes for nitrogen fixation into non-leguminous plants?
Insect resistant corn
I. Experiments on phototropism led to the discover of plant hormones
Chapters 33: Control systems in plants
A. Phototropism
i. Growth of a shoot towards light
- cell on dark side elongate faster
Fig. 33.1
AIM: How are hormones used by plants in regulation?
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
C. The five major types
AIM: How are hormones used by plants in regulation?
i. Auxin - class of molecules that affects plant growth patterns
c. Geotropism (gravitropism)
- positive geotropism: roots grow toward pull of gravity
- auxins have opposite effect in roots
- Result: root bends downward
- they still concentrate on lower side of a sideways root, but this INHIBITS elongation.
Fig. 33.3
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
C. The five major types
AIM: How are hormones used by plants in regulation?
i. Auxin - class of molecules that affects plant growth patterns
c. Auxin made in apical meristem of terminal bud
- inhibits development of lateral (axillary) buds
- mechanism of apical dominance
- also made in root apical meristem… inhibit formation of lateral roots
Taller seedlings received auxin (Fig. 33.3A)
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
C. The five major types
AIM: How are hormones used by plants in regulation?
i. Auxin - class of molecules that affects plant growth patterns
d. How do auxins cause elongation?
- hypothesis: they weaken cell walls
- stimulate proteins to pump protons (H+) into cell wall- activate enzymes to break H-bonds b/w cellulose fibers- cells swell as more water can now fit within due to cell wall stretching
Fig. 33.3
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
C. The five major types
AIM: How are hormones used by plants in regulation?
i. Auxin - class of molecules that affects plant growth patterns
e. Other effects of auxins
- induces division in vascular cambium (promotes growth in diameter)
- produced by developing embryo
- promotes fruit growth
- some plants develop fruit w/o fertilization if you spray them with auxin
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
C. The five major types
AIM: How are hormones used by plants in regulation?
ii. Cytokinins (kinins)
a. Class of growth regulators that promote cell division (cytokinesis)
b. Produced mainly in roots
c. Effects of kinins are influenced by concentrations of auxins
- auxins from terminal bud inhibit axillary bud growth- cut off terminal bud- cytokinins from roots can now activate axillary buds (auxins overpower cytokinins)
Fig. 33.4
d. Auxins and cytokinins are antagonistic hormones
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
C. The five major types
AIM: How are hormones used by plants in regulation?
ii. Cytokinins (kinins)
e. Other effects of cytokinins- affect root growth and differentiation
- delay aging (florists sometimes spray cytokinins onto flowers)
- breaking seed dormancy (germination)
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
C. The five major types
AIM: How are hormones used by plants in regulation?
iii. Gibberellins
Fig. 33.5
a. History of discovery- Fungus of genus Gibberella
- infects rice seedlings, causes them to grow very tall
- rice topples over and dies before flowering
- Japanese called it “foolish seedling disease”
- Japanese scientist discovered chemical released by the fungus that caused disease- named it Gibberellin- it was later discovered to exist naturally in plants
Foolish seedling diseased plants
Control plants
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
C. The five major types
AIM: How are hormones used by plants in regulation?
iii. Gibberellins
b. More than 100 knownc. Produced in roots and young leavesd. Stimulates stem elongation and cell division in stems
- enhances auxins
e. Enhance fruit development
sprayed with gibberellins
control
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
C. The five major types
AIM: How are hormones used by plants in regulation?
iii. Gibberellins
f. Terminate seed and bud dormancy (activate them)
g. Induce some biennial plants to flower during 1st year of growth
- spray seeds with gibberellins and they germinate regardless of environmental requirements
- naturally: when seed absorbs water, embryo triggered to release gibberellins
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
C. The five major types
AIM: How are hormones used by plants in regulation?
iv. Abscisic acid (ABA)
a. Inhibits many plant processes
- Ex. inhibits germination
- must inactivate ABA for germination to occur
- inactivation triggered by cold temperature in some seed (winter inactivates for spring germination)
- seeds activated by water: water flushes ABA out of seed- prominent in desert seeds after a hard rain:
Fig. 33.6
b. Ratio of gibberellins to ABA determines germination in many seeds (antagonistic hormones)
c. ABA signals stomata to pump out K+ when plant wilts
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
C. The five major types
AIM: How are hormones used by plants in regulation?
v. Ethylene
a. History- observed that fruit ripened in sheds with kerosene stoves
- hypothesized that heat caused ripening
- kerosene stoves were replaced with cleaner-burning stoves
- fruit did not ripen as quickly
- need to modify hypothesis
- ethylene is a gaseous byproduct of burning kerosene
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
C. The five major types
AIM: How are hormones used by plants in regulation?
v. Ethylene
c. Ethylene triggers fruit ripening and other aging processes (e.g. apoptosis)
b. Plants produce ethylene
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
C. The five major types
AIM: How are hormones used by plants in regulation?
v. Ethylene
- ethylene diffuses from fruit to fruit through air (it’s a gas!)
d. Fruit ripening
(one bad apple does spoil the lot)
- triggers enzymatic breakdown of cell walls (softens fruit)
- triggers conversion of starch to sugar (sweetens fruit)
- new scent and color attracts animals (operant conditioning) to eat and disperse seeds- what would happen if you put fruit in a plastic bag and sealed it?
- many fruits are picked green, placed in large tanks, and ethylene is pumped over them for ripening
Fig. 33.7
- CO2 inhibits action of ethylene (slows ripening): pick apples in AUTUMN, pump CO2 over them to inhibit ripening, and sell the following summer
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
C. The five major types
AIM: How are hormones used by plants in regulation?
v. Ethylene
- color change
e. Falling leaves
- leaves lose chlorophyll unmasking other pigments
- new pigments made as well
- leaves stripped of essential elements before falling off
- petiole separates from stem
1. Abscission layer Fig. 33.7
- region of separation (parenchyma cells with thin walls, weakened by enzymes)
- triggered by increasing levels of ethylene and decreasing level of auxin (antagonistic hormones)
2. Triggered by shortening days
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
D. Hormones used extensively in agriculture
AIM: How are hormones used by plants in regulation?
i. Ex. Low dose of auxins to prevent fruit from falling off before being picked
Fig. 33.8
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
E. Growth responses and biological rhythms in plants
AIM: How are hormones used by plants in regulation?
i. Tropisms
Fig. 33.9
b. Types
a. Orient plant growth toward or away from environmental stimuli
1. Phototropism
2. Gravitropism (geotropism)
II. Five major types of plant hormones regulate growth and development
Chapters 33: Control systems in plants
E. Growth responses and biological rhythms in plants
AIM: How are hormones used by plants in regulation?
i. Tropisms
Fig. 33.9
b. Types
a. Orient plant growth toward or away from environmental stimuli
1. Thigmotropism
- growth or movement in response to touch (Greek, Thigma, touch)- Ex. Tendril of pea plant
i. Grows straight until it touches somethingii. Contact causes cell to grow at different rates on opposite sides of tendril (just like phototropism and gravitropism)
- slower growth in area of contact- result: plant coils around branch- great for support while heading for sun (phototropism)
III. Lichen is not to be confused with plants
Chapters 33: Control systems in plants
A. Lichens
AIM: How are hormones used by plants in regulation?
i. Associations of millions of algae or cyanobacteria held in a network of fungal hyphae
a. Mutualism is so tight that lichens are named as a single species
b. Photoautotrophs supply fungus with food, and fungus gives photoautotrophs a suitable environment to live
Fig. 17.8
c. Can live where little or no soil (recall primary succession)
IV. Kingdom Fungus
Chapters 33: Control systems in plants
A. Fungus
AIM: How are hormones used by plants in regulation?
Fig. 17.16
b. Fungi are heterotrophs that absorb food after digesting with enzymes outside their body
a. Greek, mycos, fungi (mycelium, mycorrhizae, etc…)
c. Often saprophytes
d. Cells have cell wall made of chitin
e. Mushroom, mold and yeastf. Most reproduce sexually (fertilization) and asexually (spores or fragmentation)
- spend most of life in haploid form
g. Mushroom is spore-bearing fruiting body of a fungus