Chapter 21

Plant Nutrition and Transport

21.1 Nutrients from Soil and Air

ExperimentsAristotle - soil provides substanceVan Helmont - water provides

substance (mass)Willow tree

Hales - air provides substance

Air = CO2 --> photosynthesis --> sugars

Water = H2O --> H - photosynthesisSolvent for other molecules80-85% of mass

Soil = inorganic minerals

Minerals

17 chemical elements needed3 are not minerals; C, O, H

Macronutrients; large quantitiesNitrogen - protein and NA synthesis

Sulfur - protein synthesis

Phosphorus - NA and ATP synthesis

Potassium -protein syn. & osmosis regulation

Calcium - cell wall formation & enzyme activity

Magnesium - chlorophyll synthesis & enzyme activity

Other Minerals

• Micronutrients (small quantities)• Boron; Essential for seed and fruit development• Copper: carbohydrate and nitrogen metabolism• Iron; Essential for formation of chlorophyll• Chloride: salt effects (stomatal opening• Manganese: formation of chlorophyll; catalyst• Molybdenum: nitrogen and sulfur metabolism,

protein synthesis• Zinc: catalyst and regulator; energy production,

protein synthesis, growth regulator

Nitrogen

Produce proteins, nucleic acids, and hormonesUsually deficient

80% of atmosphere (N2)

Plants can only absorb NH4 or NO3

break down organic material into ammonia (NH4)

NH4 to NO3

N2 to NH4

Nitrogen-fixing Bacteria

Legumes: peas, beans, peanutsroot nodules: NF bacteria on roots

MutualisticBacteria fix (convert) nitrogen

Plant provides carbohydrates

Crop rotationSoybeans have NF bacteria

Convert tons of nitrogen

Corn depletes nitrogen

Fertilizers

SyntheticNitrogen

Phosphorus

Potassium

Plant doesn’t store nutrients

Leftovers are in soil and can contaminate runoff water

Polluted water goes into rivers and lakes

Do Now Questions

How does transpiration allow water to flow in a plant?

What is a sugar sink?

Why does a carnivorous plant need to eat insects?

21.2 Vascular TissueRoots absorb water and minerals root hairs: tiny outgrowths of root’s epidermal cells

Increase surface area

root pressure: helps push water through xylem; usually at night

Minerals move through the cells to xylem; cytoplasmic channels endodermis: waxy layer of cells surrounding the vascular tissue

Prevents water and mineral leakage

Water enters by osmosis

Water Movement

transpiration: loss of water through leaves due to evaporation, generates the pull of sap upward

Cohesion -

water sticking to

itself

Adhesion -

water sticking to

unlike molecules;

cellulose in xylem

Regulating Water Loss

TranspirationUpward transport

Evaporative cooling

Water loss from plantMaple Tree = 220L per hour in the summer

Stomata regulate transpiration guard cells: cells around each stoma that open and close by changing shape

Stomata

Day = open to allow CO2 in

Low CO2 = K accumulation; water flows in and swell the guard cells

Night = closed

2 Types of Xylem

tracheids: long cells with tapered ends

vessel elements: wider and shorter

Form tubes; inner cells died and left lignified cell walls

PhloemTransports sucrose and other organic compounds with water sieve-tube members: chain of cells in which phloem sap flows

Remain alive, but lose nuclei and other organelles

companion cells: cells alongside sieve tubes that provides proteins

Sugar Sink

Phloem moves sugar from where it is made (leaves) to where it is needed

Sugar sink: sugar stored or usedFruits

Roots

Shoot tips

Summer - beat, potatoes

Pressure-flow

Sugar is actively transported into a sieve-tube member

pressure-flow mechanism: water flows from high pressure to low

MonocotsStem

Root

Leaf

DicotsRoot

Stem

Leaf

21.3 Unique Adaptations

Carnivorous PlantsObtain nitrogen from insectsModified leaves form trapsLive in areas with poor nutrients

Bogs

Venus flytraps, sundews, pitcher plantsConsumer and producer(photosynthesis)

Epiphytes

Grows on the surface of another plant without harming itNutrition

PhotosynthesisAbsorb minerals from rainwater

Reason for adaptationLiving on high branches brings the plant closer to sunlight

Orchids, Spanish “moss”, ferns

Parasitic Plants

Obtain nutrients from other plants

Taps into vascular tissue

Damages plant

Take away sunlight

Can kill the host by robbing nutrients

Mistletoe, fig