Chapter 8

Effects of Temperature on Greenhouse Crops

(draft book excerpts)

The most important environmental parameters that need to be controlled for optimal greenhouse climate are temperature, light, relative humidity, and carbon dioxide (CO2). Temperature is the most important single parameter in greenhouse controls as temperature has a significant role in plant growth and development. The optimal temperature depends on the plant species grown and desired level of photosynthetic activity. Different crop species have different optimum growing temperatures and these optimum temperatures can be different for the root and the shoot environment and for the different growth stages during the life of the crop. Temperature can also affect plant quality. A plant may flower at a fast rate at high temperatures, but it may have reduced quality compared to a plant grown cooler. Grown for longer periods of time under cooler temperatures, plants generally have thicker stems, greater branching, more flowers and larger flowers. Typical greenhouse temperatures vary between 50 to 68 degrees F (10 to 20° C). Too high temperature reduces plant growth, eventually resulting in plant wilting and death whereas too low temperature limits plant growth.

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Within This Chapter: Effects of Temperature on Greenhouse Crops

  • Introduction to Effects of Temperature on Greenhouse Crops
  • Temperature Requirements for Greenhouse Crops
  • Cardinal Temperatures for Greenhouse Crops
  • Base Temperature
  • Optimum Temperature
  • Maximum Temperature
  • Cold-tolerant and Cold-sensitive Crops
  • Suboptimal Production Temperatures for Cold-tolerant Crops
  • Temperature Requirements for Stages of Crop Development
  • Day/night Temperature Differential for Greenhouse Crops
  • Day-night Temperature Relationships (DIF)
  • Height Control by DIF
  • Implementation of DIF in Warm Seasons
  • Computer Control of DIF
  • Average Daily Temperature for Greenhouse Crops
  • Temperature Influence on Plant Growth
  • Photosynthesis
  • Respiration
  • Transpiration
  • Vapor Pressure Deficit
  • Optimum Vapor Pressure Deficit Values
  • Adjusting Vapor Pressure Deficit
  • Temperature Influence of Plant Quality
  • References