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Shade Effect on Plant Growth - Part 2 of 4

Picture of palm trees with colorful sky

Components of Sun’s Energy that Support Plant Growth:

How does the sun's rays affect plant growth? Understanding the sun's differing components and their effects is key to knowing how to best support your plant's needs.

Sun’s energy is composed of:

  • PAR: Photosynthetically Active Radiation

    • Roughly equivalent to visible light spectrum 400-700nm

    • Colors below play the greatest role in plant growth

      • Blue Light 400- 495nm

      • Green Light: 495 –570nm

      • Red Light: 600-700nm

    • Far Red: 700- 800: Not as directly involved in photosynthesis but is a key component in other parts of plant development. Difficult for the eye to see, appears to be a deep red

  • Heat/Temperature

  • UV (A and B; key for flavonoid production)

    • UVA 315-400 nm;

      • Stem length and leaf breadth

      • Increases flavor and develops anti-oxidants

      • Helps cell wall strengthen to provide protection

      • Too much reduces efficiency of photosynthesis

    • UVB: 280-315nm

      • Starts production of flavonoids and anthocyanins

      • Too much can cause various stress responses


iPhone with app for measuring PAR
Example of tool used to measure to PAR

Other Aspects of the Sun’s influence on plant growth:

  • Daily Light Integral:

    • Amount of PAR light received by a plant in 24 hours

    • Measured in Photons of PAR per square meter per day (mol/m2/day)

    • Different plants need different DLI for optimal photosynthesis

  • Photosynthetic Photon Light Density

    • Amount of PAR received by plant at a given time

  • Location of sun in the sky- indicates to plants the length of the day

    • Important to plants sensitive to specific photo-periods, which influences flowering

Part 3: We will discuss how shade can directly impact your plants' growth.


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