Lecct #2 Factors Controlling Plant Growth.pptx

7/30/2019 Lecct #2 Factors Controlling Plant Growth.pptx

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List 7 factors controlling plant

growth.

Plant Physiology

Lecture #11/12/09

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Genotype

Soil texture & structure

Water Poor drainage

Soil porosity

Fine texture soils: cold soils Fine textured soils have high CEC

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List 3 ways genotype control

plant growth.

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Genotype

Inherited traits

Phenotype

Genotype can be modified base on where crop is

grown.

Phenology

Refers to the timing of the appearance of plant

structure (i.e emergence of leaf)

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How does soil texture/structure

affect plant growth?

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Fine textured soil

Has to do with feel of soil

Poor drainage (prone to water logging-H2S)

Anoxia

Anaerobic respiration/fermentation due to buildup of

CO2

pH disolves

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How does water holding capacity


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Water holding capacity

Water available

Can be detrimental

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Define Anthesis

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the period during which a flower is fully open

and functional.

It may also refer to the onset of that period.

Once flowers are fertilized

Wilts after 6-days

The gymnosphores emerges

Stops expanding in 35 days

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http://en.wikipedia.org/wiki/Flowerhttp://en.wikipedia.org/wiki/Flower


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How does poor drainage affect

plant growth?

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May impede rood development

Causes compaction (high boldensity)

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What can be done in high

boldensity soils?

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Knife it across back and forth (aerated)

Not good for root crop until soil is improved.

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How does soil porosity affect

plant growth?

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Formed in clay soils

Soil pores are filled

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How does fine soil texture affect

plant growth?

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These are cold soils (clay)

Must do something to increase temperature

Warm soil

Increases organic matter to increase air

Tilling will warm up soil or remove cold

Cold

Affect nutrient uptake

Tomatoes will not develop in warm climate

Phosphorus uptake problematic

Produce purple tinge on leaves

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How does fine textured soils (with

high CEC) affect plant growth?

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Increases buffering capacity

Can be problematic in hydroponic situation

(must monitor pH closely).

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How does soil texture in general


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Arrangement of particles

Big/bulk vs smaller particles

These come together (aggregate) into whole

(flocculaton) through Tillage

Organic matter

cations

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What bulk density have to do

with plant growth?

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Bulk density range from 1 to 1.2

It is a mass/volume relationship

It is a function of how compact the soil is.

The bulk density of soil is inversely related tothe porosity of the same soil. The more porespace in a soil the lower the value for bulk

density. The more pore, the less water retention,

drainage

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http://en.wikipedia.org/wiki/Inverse_relationshiphttp://en.wikipedia.org/wiki/Porosityhttp://en.wikipedia.org/wiki/Porosityhttp://en.wikipedia.org/wiki/Inverse_relationship


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Define relative humidity

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It is the measure of the moisture content in air

at certain temperature

It is expressed in percentage

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How is relative humidity related

to transpiration?

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RH affect rate of transpiration

Mass flow (water uptake)

Nutrient

Helps improve temperature around leaves

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List 7 ways relative humidity


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By influencing water potential (positive-good)

It affects rate of photosynthesis (Pn)

It affects rate of transpiration (as water

evaporates from leaf, helps cool it) It affects nutrient translocation

Affects plant temperature

Influences moisture condensation

Guttation (related to pressure withing leaf) Water at tip of leaf

Controls opening and closing of stomates

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How is high humidity affect

stomata opening ?

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High humidity increase the stomate opening

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What happens when there is not

enough CO2?

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Photorespiration occurs and plant uses

Oxygen instead of photosynthesis.

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What is PAR?

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Stands for photosynthetic active radiation

Range 400-660 nm

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What is the relationship between

stomata and VPD?

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Under low light, stomata openings are more

sensitive to VPD.

When VPD is high (and low light conditions)

stomata regulation by light and CO2 flux is

weakened and regulation by VPD is

strengthened.

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What are the two main physiological

impacts Relative humidity have on

plants?

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Transpiration water loss

Direct impact

Related to vapour pressure

Decreases in atm moisture

Increases vpd between air and sat. vp in leaf/ surface

Opening and closing of stomates

Increase water loss will close stomate

High CO2 (outsite or inside) will also close stomates ?

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How does leaf respond to small

vapor pressure?

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Leaf water loss is proportional to change in RH

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How does plants respond to

large vpd?

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There is no proportionality

Stomates will close and

There is a decrease in transpiration water loss

Pn closes

Pn decreases CO2

Only residual Pn continues

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Do all crops responds favorably to

relative humidity? Give example.

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No

Sweat potato: at RH 50% and 85%

Increase in biomass

Increase in Pn

Increase in stomata conductance (.3)

Red kidney beans: at 30 to 100% RH

Reduction in all of the above

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What is Harvest index?

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A ratio

Root mass/ total plant mass

If HI is 80%, that means 80% of plant is edible

HI gives relative % of crop harvested part that is

edible

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What is the field capacity?

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The moisture that remains after alowed to

freely drain

Most plant grow poorly in soils above FC

Below FC soil is dry

Plant wilting

Cucumbers and tomatoes

Stop growing

Develop purple tinge (respond to low moiture)

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How can soil pH be modified?

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By liming (calcite or Ca++)

dolomite

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What is the prefered pH for plant

growth?

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pH between 6-7

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How to treat high pH soils?

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Application of

SO4 type fertilizer

Peat moss, perlite/ peat, vermiculite

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Distinguish betweensoil separates

soil texture

soil texture class

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Soil separates refer to :sand, silt, and clay

Soil texture refers to the feel of the soil

Soil texture class refer to

Amount of sandy loam and clay that is in soils

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How do soil texture affect plant

growth?

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Fine texture soil

Poor drainage

Prone to water logging

Impede root dev

Generally cold soils

High water holding capacity

Heavy and difficult to till

Affects porosity

Low microbial activity

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What is the role of the middle

lamella?

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Gives rigidity to cells

Documents

Lecct #2 Factors Controlling Plant Growth.pptx