i. nutrients from soil and air

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


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


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


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





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:





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)





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


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



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



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:



B Stomata


Fig. 32.4

1. opening stomata- What stimulates guard cells to take up K+?

a. sunlight, low CO2, circadian rhythm (biological clock)



B Stomata


Fig. 32.4

2. Closed stomata- actively pump out K+- water follows passively (osmosis)- cells sag and stomata close:



B Stomata


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)


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)



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)



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


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


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


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


Corn growth in nitrogen rich (left) vs. nitrogen poor (right) soil

Fig. 32.6

IX. Root hairs take up cations using cation exchange


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


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


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

Fig. 32.12

Sundew video

http://www.greatneck.k12.ny.us:16080/GNPS/SHS/dept/science/truglio/video/32-12C-SunDewTrapVideo-B.mov

XII. Most plants depend on bacteria to supply nitrogen


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


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


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


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


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. mechanism

iii. What causes different growth rate?

(video)

http://www.greatneck.k12.ny.us:16080/GNPS/SHS/dept/science/truglio/video/33-01-PhototropismVideo-B.mov



B. Experiment done by Darwin and his son Francis

i. Observation - grass seedlings grow toward light only if shoot tips were present:

Fig. 33.1




B. Experiment done by Darwin and his son Francis

i. Observation - grass seedlings grow toward light only if shoot tips were present:

Fig. 33.1


ii. Conclusion - tip responsible for sensing light- chemical signal must be sent from tip



C. Follow-up experiments done by Peter Boysen-Jensen

i. Experiment: put permeable gelatin block b/w tip and bottom of shoot or impermeable mica

Fig. 33.1


ii. Result - phototropism occurred with permeable gelatiniii. Conclusion - chemical signal diffusing through gelatin from tip



D. Frits Went extracted the chemical messenger (1926)

i. Experiment:

Fig. 33.1


- put tip on agar (permeable) block to get chemical signal (hormone) into block

- place block on different parts of cut shoot:



D. Frits Went extracted the chemical messenger (1926)

ii. Conclusion:

Fig. 33.1


- blade bends away from side with chemical

- chemical stimulates cell to elongate

- called the chemical “auxin” (Greek, auxein, to increase)

Aside: Not all plants work this way

II. Five major types of plant hormones regulate growth and development


A. Affect growth/development by affecting division, elongation and differentiation

Pg. 662


B. Trigger signal transduction pathways (just like in animals)i. Turn genes ON/OFF

ii. Inhibit or activate enzymes

iii. Changes in membrane properties

C. Produced in growing parts of plants (apical meristem; young, growing leaves and developing seeds)



C. The five major types


i. Auxins - class of molecules that affects plant growth patterns

a. IAA = indolacetic acid - the major auxin of plants

b. Phototropism

- Side receiving sunlight has reduced auxin concentration

- auxin causes shaded side to grow more quickly

- IAA is associated with phototropism

IAA





i. Auxin - class of molecules that affects plant growth patterns

c. Geotropism (gravitropism)

- growth of plant towards or away from gravity

- negative geotropism: shoots grow upward, away from gravity

- gravity causes auxins to be more concentrated on lower side of horizontal plant and less concentrated on upper side.

- cells on lower side elongate (grow) quicker than on upper side…plant bends upward

(video)

http://www.greatneck.k12.ny.us:16080/GNPS/SHS/dept/science/truglio/video/33-09A-GravitropismVideo-B.mov






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






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)






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






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. 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. Cytokinins (kinins)

e. Other effects of cytokinins- affect root growth and differentiation

- delay aging (florists sometimes spray cytokinins onto flowers)

- breaking seed dormancy (germination)





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





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





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





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





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





v. Ethylene

c. Ethylene triggers fruit ripening and other aging processes (e.g. apoptosis)

b. Plants produce ethylene





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





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



D. Hormones used extensively in agriculture


i. Ex. Low dose of auxins to prevent fruit from falling off before being picked

Fig. 33.8



E. Growth responses and biological rhythms in plants


i. Tropisms

Fig. 33.9

b. Types

a. Orient plant growth toward or away from environmental stimuli

1. Phototropism

2. Gravitropism (geotropism)



E. Growth responses and biological rhythms in plants


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


A. Lichens


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


A. Fungus


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

hyphae

i. nutrients from soil and air

Documents

xylem water

xylem vesselb

waterminerals xylem

xylem sap upwarda

plant nutrition

cellulose walls of xylem

xylem waxy belt

adhesion water