4-Basic Needs of Plants

8/3/2019 4-Basic Needs of Plants

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THE BASIC

NEEDS OFPLANTS



What is a Plant?

• Immobile

• Make own food

• Plant parts

Leaf Stem Roots



Plant Relationships

• There are many plants in the world

• There are many types of plants in theworld

• The science of sorting and namingplants is called “Taxonomy”



What plants need:

Light AirWater Nutrients

Plant Physiology



Light

• Energy drivingphotosynthesis

• Photoperiod• Phototropism

What Plants Need

Air

• Oxygen (O2)• Carbon Dioxide

(CO2)• Component of

photosynthesis



Water

• Move water solublenutrients

• Transportphotosynthate

• Turgor pressure

• Component ofphotosynthesis

Nutrients

• 16 essentialnutrients

• “Plant Food”

What Plants Need



Photosynthesis

6H2O + 6CO2 + + = C6 H12 O6

+ 6O2 + ENERGY

Light at the Cellular Level



Light Wavelengths and the Plants



Blue Light is involved in:

• Photosynthesis• Petiole length• Internode length

• Leaf expansion• Phototropic reactions

Blue Light Wavelengths



Red Light is involved in:• Photosynthesis• Seed germination, seedling growth

• Fruit ripening• Tuber and bulb formation• Photoperiodism

Far Red Light• Regulates many development processes• Photoperiodism

Red & Far Red Light Wavelengths



• A response to theproportion of light anddark in a 24-hour period

• Photoperiodism is veryimportant in regulating

flowering

• Regulated byphytochrome pigment

Photoperiodism



Too little sun can cause:

• Stretching (etiolation) and

weak growth with longinternodes

• Large thin leaves or smallpale leaves. May have long

petioles• Loss of variegation• Reduction or loss of bloom• Pale color overall

Phototropism:Plants Outdoors and Light



Too much sun can

cause:

• Burning

• Stunting

Plants Outdoors and Light

Scorched Plant



• Also known as osmotic pressure, is a largepositive internal cell pressure caused by

dissolved compounds in the cell sap exertingpressure on surrounding cells.

• Plants wilt when turgor pressure decreases. Aslong as the cells are alive, turgor pressure can

be re-established (unless the permanent wiltingpoint is reached).

• Plants need turgor pressure to remain erect andmaintain the water column for transpiration.

Turgor pressure

Water



Cohesion Tension Theory

• Polar water molecules stick together by hydrogen

bonds; this is “cohesion”. • Water sticks to walls of xylem; this is “adhesion”.

• Xylem provides the structure for a water column.• Water evaporates from leaves via transpiration,

creating a pull or tension on the water column.Tension in the xylem lowers the water potential,so the plant/tree can pull water in from the soil.

Water Movement in the Plant:



Stomates



Stomates close due to:

• Water stress• High temperature

• High carbon dioxide (CO2)• Darkness• Transpiration rates increase when:A rise in temperature occurs (each 10 oC

rise in temperature doubles thetranspiration rate)Wind and low humidity increase water

evaporation from leaf surfaces

Stomatal regulation



Stomata open in day,close at night. Must letwater out (from

respiration andtranspiration) and CO2in (for photosynthesis),so a tradeoff between

losing too much water& photosynthesis ismade.

Transpiration/Photosynthesis Compromise



Water Availability in Soil



Without oxygen, roots dieRoots can carry on anaerobicrespiration for a short timeSymptoms of injury you might see:

• Decreased shoot growth• Chlorosis (yellowing of the leaves)

• Leaf epinasty (petiole elongation)• Leaf abscission (shedding of the

leaf or flower)

Waterlogged Soils



Oxygen is needed for:

Cell respirationRoot growth and

maintenance

AIR



C6 H12 O6 + 6O2 = 6CO2 + 6H2O +ENERGY

Respiration equation is essentially theopposite of photosynthesis. Instead of

using the sun’s energy to make food, ituses the food and releases chemicalenergy

Cell Respiration



Plants can remove pollutants from air, butcan also be damaged by them. A one acre

Christmas tree farm can remove up to1300 kg of airborne pollutants per year.

Pollutants:

• Sulfates• Sulfur dioxide• Nitrates• Ozone

Airborne Pollutants



Air pollution damage can cause:

Stunting

Loss of leaves Damage to leaves (reduced sugar

production)

Reduced (or non-existent) fruit yield Repeated severe exposure can

eventually cause death

Airborne Pollutants



Soil Structure andNutrients in Soils



Soil Structure

Pore space is 50% ofa typical soil

Usually 5% of the soil

is organic matter



Organic Matter in Soils

Typicalcomposition ofsoil organicmatter



Soil OM acts as a bank for plantnutrients.

Soil OM holds metal micronutrients ina soluble form, available for uptake.

Soil OM is important in maintaininggood soil structure and beneficial soil

microorganisms. Soil OM acts as a buffer to pH

changes.

Organic Matter in Soils (OM)



Particle sizes and surface area:

Sand: Largest particle with smallest surfacearea. Doesn’t hold water or nutrients well.

Limited chemical properties.

Silt: Smaller than sand. More surface area.Holds water & nutrients well. Good CEC.

Clay: Smallest particle size. Has a strongaffinity for water & nutrients. Has thousands oftimes more surface area than silt and millionsmore times than sand. Very good CEC.

Soil Particle Sizes



Macronutrients• Nitrogen, phosphorus, potassium,

manganese, calcium, sulfur

Micronutrients• Iron, magnesium, copper, boron,

molybdenum, chlorine, zinc

All together now!• C HOPKNS CaFeMg Cl Mn• C Hopkin’s Café, Mighty Good

(Closed Mondays)

Essential Nutrients



Soil pH and

Nutrient Solubility

Alkaline soils areconsidered to be

above pH 7.0Acid soils are belowpH 5.5

Most garden plantsprefer soils betweenpH 6.5 and pH 7.5



‘Alkaline’ Soil Crops ‘Acid’ Soil Crops

Beans Beets

Broccoli Cabbage

Carrots Cucumbers

Cauliflowe Lettuce

Onions Spinach

Squash Tomatoes

Some Common GardenCrops and pH



END OFSESSION

4-Basic Needs of Plants

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