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