chapter 10 – transport in plants. transport in plants water and mineral nutrients must be...
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Chapter 10 – Transport in Chapter 10 – Transport in PlantsPlants
Transport in plantsTransport in plants
Water and mineral nutrients must be absorbed by the roots and transported throughout the plant
Sugars must be transported from site of production, throughout the plant, and stored
Cellular transport Cellular transport mechanismsmechanisms
Osmotic potential, solutes, and Osmotic potential, solutes, and water movementwater movement
Water potential influences Water potential influences water movementwater movement
Water potential (Ψ) of a cell:
Ψcell = ΨΡ + ΨΟ
Ρ = pressure potential
Ο = osmotic (solute) potential
ΨΨpp - Pressure potential (turgor) - Pressure potential (turgor)
Low Ψp High Ψp
ΨΨΟΟ – – Osmotic (Osmotic (Solute) Solute)
potentialpotential
Pure water ΨΟ = 0
All solutions, ΨΟ < 0
As solute concentration increases, Ψcell …
Water movement in plantsWater movement in plants
Movement from high Ψcell to low Ψcell
Occurs in the xylem Involves adhesion, cohesion, and
pressure
Adhesion and cohesionAdhesion and cohesion
Water Water transporttransport
Tension-cohesion theory Tension-cohesion theory explains xylem transportexplains xylem transport
Water is drawn up the plant by transpiration of water from stomata
A water potential gradient A water potential gradient creates tensioncreates tension
low ψ
Transpiration creates tension
higher ψ
cohesion
higher ψ
lower ψhigher ψ
lower ψ higher ψ highest ψ
lower ψ
Water transport animationWater transport animation
Transpiration & water Transpiration & water transporttransport
Importance of stomataImportance of stomata
Regulate transpiration rate– Controls rate of water uptake
Water required for photosynthesis Water required to maintain turgor
pressure Influences nutrient uptake
Regulate gas exchange– CO2 required for photosynthesis
Turgid guard cells open Turgid guard cells open stomatastomata
Guard cells & osmotic Guard cells & osmotic potentialpotential
Transpiration & photosynthesisTranspiration & photosynthesis
Ψ and transpiration rateΨ and transpiration rate In terms of ψ, can you explain
how transpiration rate is influenced by:
– Atmospheric humidity?– Wind?– Air temperature?– Light intensity?
Which of the following explains Which of the following explains why water moves into the root why water moves into the root
from the soil?from the soil?1. The water potential of the root is lower than
the water potential of the soil2. The roots exist in a hypertonic environment3. The pressure potential of the soil forces
water into the root4. Water is actively transported into the root5. The soil has a higher solute concentration
than the roots, causing water to diffuse into the roots
Stomata close whenStomata close when
1. Photosynthesis lowers CO2 concentrations in the leaves
2. Potassium ions are pumped into guard cells
3. Abscisic acid levels increase4. Guard cells become turgid5. All of these occur
A guard cell with a high A guard cell with a high
internal concentration of Kinternal concentration of K++ 1. Is in a hypertonic condition2. Has a low water potential
relative to outside of the cell3. Has a higher water potential
than outside the cell4. Both 1 and 25. Both 2 and 3
Water Water transporttransport
Sugar Sugar transporttransport
Source to sink Source to sink sugar transportsugar transport
Pressure-flow hypothesis Pressure-flow hypothesis explains sugar transportexplains sugar transport
Phloem loadingPhloem loading
Sugar transport can be Sugar transport can be explained by water potentialexplained by water potential
Transport in plantsTransport in plants
Water and mineral nutrients are absorbed by the roots and transported throughout the plant by tension-cohesion
Sugars are transported from site of production (source), throughout the plant, and stored (sinks) by pressure-flow
Mineral Mineral nutrition & nutrition & uptakeuptake
Soils and plant nutritionSoils and plant nutrition
14 essential mineral nutrients– N,P,K,S,Ca,Mg,Fe,Cl,Mn,B,Zn,Cu,Mo,Ni
3 essential non-mineral nutrients– C,H,O
– What makes these nutrients essential?
Magnesium and Magnesium and photosynthesisphotosynthesis
Nitrogen and amino acidsNitrogen and amino acids
Nitrogen, phosphorus & DNANitrogen, phosphorus & DNA
Potassium and cell functionPotassium and cell function
Macronutrients vs. Macronutrients vs. micronutrientsmicronutrients
Fertilizers Fertilizers Fertilizer analysis (N-P-K) Analysis varies depending on
growth objectives
How can essential elements How can essential elements be determined?be determined?
HydroponicsHydroponics
Recreational hydroponicsRecreational hydroponics Home hydroponics systems
A soil profileA soil profile
Soil composition– Sand, silt, clay– Humus– Microorganisms– Animals
Mineral nutrients exist as ionsMineral nutrients exist as ions
Cation exchange allows Cation exchange allows mineral ions to be absorbed by mineral ions to be absorbed by
rootsroots
Cation exchange and HCation exchange and H++
Mineral nutrient transportMineral nutrient transport
How does cation exchange How does cation exchange affect soil pH?affect soil pH?
Raising soil pH with limeCa(OH)2 + 2H+ Ca2+ + 2H2O
Soil pH and mineral nutritionSoil pH and mineral nutrition
Different types of plants have different soil pH requirements (ex. truffles, filbert trees, and alkaline soils)
Which of the following Which of the following statements concerning plant statements concerning plant
nutrition is/are true?nutrition is/are true?1. Macronutrients are large elements and
micronutrients are small elements2. Macronutrients are essential to plant
growth and micronutrients are not essential3. Macronutrients are absorbed from the
atmosphere and micronutrients are absorbed from the soil
4. All of these are true5. None of these are true
Cation exchangeCation exchange1. Occurs when plants release O2 and absorb
CO2 through their stomata2. Involves plants releasing Ca2+ into the soil
in order to absorb H+ ions3. Involves the release of H+ ions from roots
to displace mineral nutrient ions from soil particles
4. Allows plant roots to absorb C, H, and O through their roots by converting these atoms to cations