Plant Growth Environment

Climate & plant growth

• Climate – average weather of an area– Air, Moisture, Temperature, Light

Regional climate vs. microclimate

Air

• Humidity

• Wind

• Air pollution

• Elevation (temperature)

Air and elevation

Moisture and plant growth

• Amount

• Distribution patterns

• Access (location)

• Bodies of water and climate

• Moisture stress– Deficiency, excess

Temperature and plant growth• Cold hardiness determines range

Temperature & plant growth

• Plant heat zones influence plant growth

Growth responses to temperature

• Vernalization– Period of low temperature

induces flowering (e.g. “forcing” bulbs)

• Thermoperiodism– Sugar/starch content varies with

temperature (cooler temps promote starch conversion to sugars);

– some plants grow better if night temperatures are cooler than day temperatures

Temperature and germination

Temperature and germination

• Stratification– Period of cold required to induce

germination– Required by many types of perennials,

woody species– Specific temp. and length of stratification

varies by species

Temperature stress

• Low temperature stress (p. 643, 645, 655)– Chilling– Freezing– Sunscald– Premature bolting– Cold water stress

Preventing low temp. stress

• Timing of planting

• Zone rating of species

• Protective measures (p. 604-605)– Covers– Mounding mulch, soil– Hardening (cold frame)

Heat stress (p. 643, 650)

• Sunscald– Plant relocation

Light

• Intensity

• Quality

• Daylength

Light Quality

Photoperiodism

• Growth responses to daylength– Flowering, germination, dormancy

• Mediated by pigment molecule phytochrome

Phytochrome and flowering

Manipulation of photoperiod

• Poinsettia industry

• Chrysanthemums

• Why won’t my Christmas cactus bloom?

• Photoperiodic houseplants

Phytochrome and stem growth

•Etiolation occurs in low light or dark…why?

Biotic environmental factors

• Insects

• Microorganisms

Soil (p. 610-622)

• Mineral particles

• Organic matter

• Water

• Air

• Living organisms

Soils

• Soil profile– horizons

Soil – mineral particles

Sand, silt, clay

Soil texture triangle

Organic matter

• Humus<20% humus = mineral soil

>20% humus = organic soil

– Provides nutrients, aeration– Increases water holding capacity Leaf humus

Living organisms in soil

• Microorganisms– Bacteria, fungi, algae,

protozoa, actinomycetes

• Insects– Earthworms, beetles,

nematodes, ants

• Weed seeds

How are soil organisms important to plants?

• Aerate soil

• Become humus

• Influence soil pH

• Can make soil uninhabitable

• Can compete with cultivated plants (weeds)

Plant nutrition

• 13 essential mineral nutrients– N,P,K,S,Ca,Mg,Fe,Cl,Mn,B,Zn,Cu,Mo

• 3 essential non-mineral nutrients– C,H,O

– What makes these nutrients essential?

Nutrient deficiencies

iron

zinc potassium

magnesium

phosphorus

Chlorophyll contains Mg

Amino acids contain N

DNA contains N, P

Stomata function requires K

Mineral nutrients exist as ions

• How do plants acquire mineral ions that are bound to clay particles?

Roots produce hydrogen ions as byproducts of respiration

CO2 + H2O H2CO3 HCO3- + H+

Soil pH and mineral nutrition

Different types of plants have different soil pH requirements

Cation exchange lowers soil pH

• Raising soil pH with lime* (mushroom compost contains lime)

Ca(OH)2 + 2H+ Ca2+ + 2H2O

*Never lime with manure! (ammonia produced)

Fertilizers • Fertilizer analysis

– (N-P-K)– “Complete” fertilizers (trace elements/micronutrients)

• Analysis varies depending on growth objectives

Fertilizer application

• Broadcast

• Ringing plants

• Banding

Soil analysis

• County Ag. Extension office (link)

• Home test kits

Soil cultivation

• Weed control• Soil sterilization

(pest/disease control)• Digging and forking (p.

613-614)– Aeration, soil crusting,

compaction

• Soil additives– Inorganic, organic

Home composting

Volume of additive required depends on NPK analysis