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Plant Environment: Temperature. Biological activities of most plants occur within a range of temperatures. Temperature. Temperature classification:. Cool-season plants (e.g. peas, apples, spruce trees). Intermediate-season plants (e.g. tomato, peach, Rhododendron ).

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plant environment temperature
Plant Environment: Temperature
  • Biological activities of most plants occur within a range of temperatures
  • Temperature
  • Temperature classification:
  • Cool-season plants (e.g. peas, apples, spruce trees)
  • Intermediate-season plants (e.g. tomato, peach, Rhododendron)
  • Warm-season plants (e.g. melons, citrus, Norfolk Island Pine)
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Plant Environment: Temperature
  • Plant growth rate
  • Maturation
  • Temperature influences most plant activities:
  • Fruit ripening
  • Seed germination
  • Crop quality
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Plant Environment: Temperature
  • Plant growth results from enzymatic reactions and is influenced by temperature
  • Temperature and plant growth

Plant growth rate

  • Optimum temperature for most plants 20-30oC (68-86oF); grower can adjust growth rate by adjusting temperature
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Plant Environment: Temperature
  • daytime and nighttime temperature influence growth rates of plants
  • Temperature and plant growth
  • Some plants grow taller if day temperature is greater than night temperature
  • Shorter, compact plants are produced if night temperature exceeds day temperature
  • Most plants grow better if temperature changes during the day than if temperature constant
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Plant Environment: Temperature
  • time to harvest also influenced by temperature
  • Growers calculate degree days to schedule harvests
  • Temperature and plant maturation
  • Degreesdays = average of daily minimum and maximum temperatures minus base temperature (in oF)
  • Base temperature depends on location, crop, moisture, soil and cultivar
  • Assume base temperature of 40oF and a given day with high of 75o and low 45oF. Degree days for that day = 20.
  • Harvest scheduled when degree days approaches optimum for the crop (e.g. peas = 120-170 after bloom, apples 1400-2800 after bloom)
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Plant Environment: Temperature
  • Sugar concentration in crops influenced by temperature
  • Temperature and quality of crops
  • Under warm conditions, sugar in plants converted to starch
  • Under cool conditions, starch is converted to sugar
  • Crops harvested under cool temperature sweeter
  • Brussel sprouts should be planted in summer for fall harvest
  • harvest and store sweet corn in cool temperatures to maintain sweetness (day-old corn not as sweet)
  • Cooler temperature produce brighter red flowers and fruits because anthocyanins formed from sugars
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Plant Environment: Temperature
  • Influences seed germination, root growth, water uptake
  • Soil temperature
  • Cool-season plant will not germinate if soil temperature too cold or too warm (60-70oF ideal)
  • Cold soil may slow germination and encourage rotting; called pre or post-emergence damping off
  • Roots resist water uptake in low soil temperatures; plants in cold soils may wilt because not getting enough water
  • Cuttings root faster if rooting medium is heated (70-80oF ideal for many species)
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Plant Environment: Temperature
  • Light energy that passes through greenhouse converted to heat and then trapped
  • Cooling greenhouses
  • Cooling greenhouse important even on sunny day in winter
  • Passive: vents at peak allow hot air to rise (air convection) and escape greenhouse; side vents allow cool air to enter
  • Active: exhausted with fans; often pull air through wet pad to cool (through evaporation) outside air
  • Radiation reduced Spring-Fall by shading with black clothes or white washing glass greenhouses
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Plant Environment: Temperature
  • Low temperature effects
  • Chillinginjury: plants damaged by low temperature but ice crystals did not form
  • Temperature stress
  • Tropical plants particularly sensitive to cool temperatures
  • Symptoms include: lesions, discoloration, defoliation, wilting, poor keeping quality (in fruit like bananas)
  • Freezinginjury: damage caused by freezing of water inside plant
  • Common problem for young apple trees (sunscald)
  • In winter sun can warm southwest side of trunk thawing tissue; after sunset tissue freezes and causes cell death
  • Dead bark dries in Spring and peels off, exposing wood
  • Orchards paint trunks white to reflect winter sunlight
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Plant Environment: Temperature
  • Low temperature effects
  • Freezinginjury:
  • Temperature stress

Sunscald Frost crack

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Plant Environment: Temperature
  • Winter hardiness
  • Winter hardiness refers to plants ability to tolerate or avoid freezing damage
  • Temperature stress
  • Freeze-tolerant plants allow water to move outside cells and freeze in extracellular spaces; require gradual exposure to cold (acclimation)
  • Freeze avoidance achieved by allowing some water to leave cells which increases solute concentration in cells; requires lower temperature to cause cellular freezing
  • Freeze avoidance also achieved by remaining low to ground so covered by insulating snow
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Plant Environment: Temperature
  • Winter hardiness
  • Winter hardiness of species determines where plants can grow
  • Temperature stress
  • USDA publishes winter hardiness maps based on average annual minimum temperatures; zone 1 coldest, zone 11 warmest
  • Provenance = geographic origin of plant
  • Plants from warmer zones not as cold hardy as those from colder zones
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Plant Environment: Temperature
  • High-temperature effects
  • Southwest trunk of thin-barked trees such as apples can overheat and kill vascular cambium; resembles sunscald
  • Temperature stress
  • Fruits and leaves can also become sunscalded, producing yellowish areas or dead tissue
  • Many desert plants (e.g. cacti) have adaptation to prevent heat stress such as whitish hairs to reflect sunlight and provide shade to stems
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Plant Environment: Temperature
  • Hardening off plants
  • Actively growing plant more susceptible to temperature stress than dormant plants
  • Temperature stress
  • Plants can become hardened or acclimated to temperature changes (naturally use photoperiod and temperature cues)
  • Important to slowly decrease temperature (and water) of seedlings before planting outdoors