chapter 25 nutrition and transport in flowering plants read chapter 25 in textbook (remember to look...

Chapter 25Nutrition and Transport in

Flowering Plants

Read chapter 25 in textbook(remember to look at book website)

Read 207-210 in Cliffs AP Book

Chapter 25 Overview

• Topics– Plant Nutrition and Soil– Uptake of water and minerals– Transport Mechanisms in Plants

Ch 25 Nutrition and Transport in Plants

25.1 Plant Nutrition and Soil• In the early 1600’s

a man named John Baptiste Van Helmont set up an experiment to prove plants were “soil eaters”– What was his

experiment?– What did he think he

discovered?

He planted a 5 lb. willow tree in a pot containing 200 lbs. of soil.

He watered the tree regularly for 5 years and watched it grow.

At the end of 5 years he weighed the plant and the soil. What did he expect to find? What were his results?His results:

Tree weighed 170 lbs.Pot and soil weighed a few ounces less than

200 lbs.

He concluded that the increase in weight (165#) was due to water. Was he correct?Sort of:-- plants do need water, but also CO2 and sunlight to produce carbohydrates which are the main organic components of plants. Also they absorb minerals from the soil.

• Essential Inorganic Nutrients– Can you think of a

method of growing plants that might help determine which nutrients are essential?

Hydroponics


25.1 Plant Nutrition and Soil

• Essential Nutrients– 96% of plant dry weight made up of C, H, O– Macronutrients and micronutrients needed from

environment. Examples of macronutrients:• N - for nucleic acid formation• K – cofactor for enzymes• Ca – regulator and stability of cell walls• P – nucleic acids, ATP• Mg – part of chlorophyll• S – part of amino acids and coenzymes



• Soil formation – Involves interplay of:

• Physical• Chemical and• Biological forces




25.1 Plant Nutrition and Soil• Soil – it’s not just dirt!

– Terrestrial organisms (which eat plants, or use O2) rely on soil to provide plants with everything they need except carbon dioxide (where is that from?).

– Soil formation involves physical, chemical and biological factors.

– Takes a long time – about 15 yr to produce 1 cm of soil.– Soil

• Mixture of soil particles of varying sizes (lg sandmed siltsm clay),

• Decaying organic material (humus),• Living organisms (lichens and mosses) (moles, badgers,

earthworms, millipedes)(microorganisms – protozoa, bacteria fungi), and

• Air and water

Moss in foreground, female spore of liverwort. Male

spore of liverwort.

Left - Lichens= Fungus and algae growing mutualistically.

http://www.ontariowildflower.com/moss.htm

Right - Humus

Sand, Silt, and Clay http://generalhorticulture.tamu.edu/h202/labs/lab7/mineral-particles/clay.html



http://generalhorticulture.tamu.edu/h202/labs/lab7/mineral-particles/clay.html

• Soil particles– Clay particles

• neg charged so help hold on to positive ions – keeps them from being washed away

• Acid rain can displace these positive ions

• NO3- is neg, so clay does

not hold well, so N content of clay soil is low. N fixing bacteria can help this

– Loam is 1/3 sand, 1/3 silt, 1/3 clay – good balance

Root nodules (N fixing bacteria) on

pea roots.



• Uptake of water and minerals– Water is taken up into the root cells

by osmosis.– Minerals are taken into the root

cells against their concentration gradient by active transport. Plants are able to concentrate the minerals. Uses ATP.

– water and minerals that are in soil or root hair cell, can get to xylem via:

• Pathway A (root)between cells (water)-actually travels through cell walls, not between cells. Apoplastic route.

• Pathway B (root hair)through cells (water or minerals). Symplastic route.

– At Casparian (subrin and lignin) strip water and minerals gets routed into xylem (water passively – minerals actively) by going through endodermal cells.


25.2 Water and Mineral Uptake

• Uptake of water and minerals– Minerals taken up in ionic form.– Plasma membrane has a slight

charge – makes it difficult for ions to pass through

– Takes energy – ATP supplies energy to run H pumps (proton pump).

– Chemiosmosis and electrochemical gradients set up.

• H pumped out of cell – creates more positive charge outside cell

• K ions (and other pos ions)are repelled by positive charge and move into cell

• H ions flow down conc gradient into cell, bringing neg charged particles with them

– Once the minerals are in the extravascular space, they are taken into the xylem (which is dead) passively by diffusion.



•2. Minerals diffuse inward via the plasmodesmota. Water follows by osmosis.

•3. Pericycle cells actively pump minerals out of their cytoplasm into the extracellular space around the xylem.Water follows by osmosis.

•4. Entry of the minerals raises the concentration of minerals in the extracellular space, so they diffuse into the dead xylem cells. Water follows by osmosis.

•5. Water can also take a pathway between cells until it reaches the Casparian strip.

•1. Active transport pumps minerals into the cytoplasm of root hair cells. Water follows by osmosis.



• Adaptations of roots for mineral uptake– Two symbiotic relationships

• Rhizobium bacteria fix atmospheric Nitrogen(N2) to ammonium (NH4) and nitrites and nitrates

– Root nodules in legumes (beans)– Bacteria get carbs from plant, plant gets N

• Mycorrhiza fungi– Associated with almost all plant roots– Plants get greatly increased absorptive surface and fungus breaks down

organic matter for plant to absorb– Fungus gets sugars and amino acids from plant

– Epiphytes (ex.: orchids)• “Air roots” – live on other plants but not parasitic, don’t need soil

– Parasitic plants (ex. - dodder, broomrape, pinedrops)• Invade cells of host plant

– Carnivorous plants (ex. - Venus flytrap, sundew)• Can digest insects

With mycorrhiza

Without mycorrhiza

Mycorrhizal root system washed carefully from coarse sand to reveal the intact network with external hyphae (arrow) with spores (S) produced by Glomus mosseae.

Sundew

Dodder plant (yellow because it has no

chlorophyll) parasitizing a tulip

plant.





Epiphytes growing in a tree

Proton Pump Animation

Root Nodule Formation


25.3 Transport Mechanisms in Plants

• Two main transport mechanisms– Xylem

• transports water and minerals from roots to leaves (only moves in one direction)

– Phloem• Transport organic

nutrients to cells that need them(either direction).

• Xylem– Tracheids

• Narrower than vessel elements

• Joined end to end• Pitted end walls

– Vessel elements• Larger - wider• Joined end to end• Form a continuous

hollow tube



Vessel elements – shorter and wider, water passes freely from one to the next through a perforation (area with no cell walls). Water movement faster than in tracheids.

Tracheids – narrower with tapered ends. Water passes through pits in tapered parts.

• Vessel element SEM www.DennisKunkel.com

http://www.denniskunkel.com/

• Phloem– Sieve tube

elements(cells)• Form a conducting

tube• Contain cytoplasm,

but have no nucleus• On ends are sieve

plates• Elements connected

by plasmodesmata

– Companion cells• Helper cells• Supply proteins to

sieve cells

From http://www.estrellamountain.edu/faculty/farabee/biobk/BioBookPLANTANAT.html



Seive tube elements – have sieve plates at their ends – area with pores where cytoplasm of the cells connects. Cytoplasm communicates through plasmodesmata.

Companion cells – parenchymal cells adjacent to sieve tube elements. Physiologically support the nuclei free sieve tube elements.


37.3 Transport Mechanisms in Plants• Water transport (xylem)

– Driven primarily by transpiration

– Water entering xylem is• pushed by root pressure

– Mostly at night– Water pulled in by osmosis –

pushes water up xylem– Can only raise the water up a

small distance– Can cause guttation

(stomates are closed)

• pulled by transpiration– Relies on cohesion, adhesion

and evaporation – pulls water up xylem

– At least 90% of all water taken in by roots is lost by transpiration

– Relies on stomates being open

Transpiration animations:..\..\Biology\Biology Clipart Movies Animations Sounds\Biology movies\transpiration tree animation QT 40sec.mov

• Water transport tutorial (30 sec)– ..\..\Biology\Biology Clipart Movies

Animations Sounds\Biology tutorials\plant water movement.dir



• Opening and closing of stomates– Guard cells on either side

of opening (stomate) can actively transport K in and out.

– K ion transported in increased osmotic pressure water pulled in guard cells swell and bend to open stomate

– Proton pump fueled by ATP hydrolysis pumps H ions out and sets up electrochemical gradient that favors K moving into cell.



• Animation plant leaf stomata– ..\..\Biology\Biology Clipart Movies Animations Sounds\Biology

tutorials\stomata plm2s3b[1].ram

www.botany.uwc.ac.za/.../ leaves/insideleaf2.htm http://www.pbrc.hawaii.edu/bemf/microangela/stomata7.htm




25.3 Transport Mechanisms in Plants• Factors that regulate K concentrations in guard cells;

therefore stomate opening and closing– Light reception

• Open in light (so can do photosynthesis), close in dark (to conserve water when photosynthesis can’t occur)

– Carbon dioxide concentrations• Low CO2 (in leaf) – open

• High CO2 - close

– Water• Leaf loses water starts to wilt releases abscisic acid inhibits K

transport close

– Heat • may cause increased cell resp, leading to increased CO2 leading to

closing stomates. May be a combination of lack of water and too much heat.

– Circadian rhythm • Even if plant in dark 24 hrs, stomates still open and close

Stomate movie (48 sec):

..\..\Biology\Biology Clipart Movies Animations Sounds\Biology movies\stomatal movement movie.mov

Stomata and water flow animation

..\..\Biology\Biology Clipart Movies Animations Sounds\Biology movies\Stomata[1].mov

• Stomata control summary– Factors that open stomata

• Red light and Blue light (from sunlight) that chloroplasts absorb

• Low internal CO2 concentration (high level of photosynthesis)

• Circadian rhythm

– Factors that close stomata• Dark (except CAM plants – stomata open at night)• Abscisic acid (hormone released when plant wilts)

• High internal CO2 concentrations (if photosynthesis stops)

• Circadian rhythm• Lack of water




25.3 Transport Mechanisms in Plants• Organic Nutrient

Transport (Phloem)– Experiments with girdling,

aphids, and radioactive 14 C showed phloem transports sugars

– Pressure flow model• Source (photosynthetic

cells) and sink (cells that need energy)

• Positive pressure drives the sap (can go up or down)

• Sucrose actively transported along with H+ by proton pump, water follows by osmosis

• Chemiosmotic mechanism

Pressure Flow ModelFormation

Water Transport in Xylem Formation

Water Transport in Phloem Formation

– Animation Pressure Flow Model• Plant organic nutrients movement

– ..\..\Biology\Biology Clipart Movies Animations Sounds\Biology tutorials\plant organic nutrient movement.dir



The End

http://www.indiana.edu/~oso/animations/An12.html

Ginko plant growing animation

chapter 25 nutrition and transport in flowering plants read chapter 25 in textbook (remember to look...

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