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Water Relation to Plants Properties of Water Associated Uses of Water Dissolves soil minerals, sugar, amino acids, widest range of any liquid! Polar Solvent

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Water l.jpg

Water

Relation to Plants


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Properties of Water

Associated Uses of Water

Dissolves soil minerals, sugar, amino acids, widest range of any liquid!

Polar Solvent

Does not compress, so turgor pressure supports plant tissue, permits flow of material in xylem (transpiration) and phloem (translocation)

Hydraulic Fluid

Reactant: CO2 + H2O -> O2 + CH2O

Product: CH2O + O2 -> H2O + CO2

PSN

Reactive

Resp

High Specific Heat

Heat Buffer: 1 Calorie = 1 Liter 1°C

Water liquid->gas removes energy

from surface

Evaporative cooling

High Heat of Fusion


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Sources of Water

Precipitation: Fog, Mist, Rain, Snow, Sleet, Hail

Runoff: Brook, Creek, Stream, River

Water Table: Puddle, Pond, Lake (Ocean not freshwater)

Soil Water: Most useful for plants

Aquifers: porous rock, wells, artesian wells, springs


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friable

Mud

Field Capacity

Wilting Point

Dry Soil

drips!

heat!

Gravitational Water

Capillary Water

Hygroscopic Water

Runoff

Unavailable

Held between soil particles

Erosion

Available to plant roots!


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Irrigation Methods

Sprinkler: Wastes more than 50% of water used

Water drops on leaves: dead spots

Humidity leads to fungal diseases

Kills “eggs” (zygotes!) of many “bugs”

May apply fertilizer/insectide at same time

Surface: Less wasteful, no water spots, yes fertilizer

Not pesticide unless “systemic”

Furrow irrigation (trenches between rows of field)

Flood irrigation (un-level field, one furrow at high end)

Trickle: Even less wasteful, method in our greenhouse

Computer programming for even more even conditions

Wick: Capillary mat with ebb-flow pumping of fertilizer and water…plants take only what is needed.

Natural: 4 inches of rain needed per month.

Watch the news, read USA today, surf Wunderground.com.

Irrigate only when needed…IF needed…MOST CONSERVATIVE!


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How Much? How Often?

Many people kill their plants with kindness (8 glasses per day)

Keeping soil friable:

Between Field Capacity and

Wilting Point

Water to field capacity

Allow to sit in sun for many days (week) until wilting

You don’t need a Green Thumb!

Dirty Finger Method:

Put Finger in Soil

  • If finger is wet, cold, dirty: NOT YET!

  • If finger is dry, warm, clean: OK to Irrigate


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When should I irrigate?

Mid-day?

Remember the water spots, magnifying lenses?

Evening?

Soil warm from afternoon, add water = fungi

Morning?

Soil cool for less evaporation waste

Spots evaporate from leaves before sun gets high

Other Pointers:

Preserve water in soil with mulch

Proper spacing of plants avoids soil heating and evaporation

Water less often but more deeply to encourage deeper rooting

Lighten waterlogging clay soils with sand or perlite!


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Plant Factors Affecting Water Needs

More

Less

It is a seedling

It is growing rapidly

It is reproducing (flowers and fruits)

It is dormant

It has succulent leaves

It has waxy leaves

It has hairy leaves

It has thin, fine, dissected leaves

It has deep roots


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Environmental Factors Affecting Water Needs

More

Less

It is in a clay soil

It is in a sandy soil

The temperature is hot

The wind is blowing

The humidity is high

The sun is bright (no clouds)


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Symptoms of Overwatering

Symptoms of Underwatering

Organs swell, crack open

Fungi thrive (Damp-off)

Yellowing of leaves

Root Death by Asphyxiation

Wilting

Growth Inhibition (Dwarfing)

Leaves with brown tips and edges

Blueing of leaves

Abscission of leaves

Wilting

Notice that the shared symptom is WILTING!

This leads to much overwatering!

These symptoms are easily explained by understanding OSMOSIS!


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0 M

hypotonic

Osmosis: the passive movement of water from a place that is purer water to a place that is more polluted

  • weight increase

  • size increase

  • turgor pressure increase

  • influx stops when it cannot overcome wall pressure

0.3 M

0.25 M

0 M

hypotonic

Water moves into the cell


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3 M

Osmosis: the passive movement of water from a place that is purer water to a place that is more polluted

  • weight decrease

  • size decrease

  • turgor pressure to 0

  • efflux stops when the concentrations match

  • plasmolysis: membrane pulls away from cell wall

0.3 M

3 M

cytosol

solution

3 M

hypertonic

Water moves out of the cell


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Osmosis: the passive movement of water from a place that is purer water to a place that is more polluted

  • no weight change

  • no size change

  • no turgor pressure change

0.3 M

0.3 M

isotonic

Water moves into and out of the cell at same rate!


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