1 / 14

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 ).

jana
Download Presentation

Plant Environment: Temperature

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. 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)

  2. Plant Environment: Temperature • Plant growth rate • Maturation • Temperature influences most plant activities: • Fruit ripening • Seed germination • Crop quality

  3. 0 15 30 50 temperature 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

  4. 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

  5. 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)

  6. 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

  7. 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)

  8. 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

  9. 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

  10. Plant Environment: Temperature • Low temperature effects • Freezinginjury: • Temperature stress Sunscald Frost crack

  11. 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

  12. 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

  13. 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

  14. 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

More Related