Effect of Light in Horticulture

Light plays a crucial role in plant growth, development, and productivity in horticulture. It affects photosynthesis, flowering, fruiting, and overall plant health. The three key aspects of light that influence horticultural crops are light intensity, light quality, and photoperiod.

1. Light Intensity (Brightness of Light)

    Light intensity significantly affects crop production by directly impacting the rate of photosynthesis which is the process by which plants convert light energy into chemical energy to grow; 

    higher light intensity generally leads to increased photosynthesis and thus, greater crop yield, but too much light can also damage plants, meaning each crop has an optimal light intensity range for best growth. 
    Key points about light intensity and crop production:
    • Photosynthesis:
      As light intensity increases, the rate of photosynthesis typically increases, allowing plants to produce more carbohydrates (sugars) needed for growth. 
    • Optimal light range:
      Each plant species has an optimal light intensity range where photosynthesis is maximized; exceeding this range can lead to stress and reduced growth. 
    • Low light effects:
      When light intensity is too low, plants may become spindly with pale leaves due to reduced photosynthesis and slower growth. 
    • High light effects:
      Excessive light intensity can cause leaf scorching, bleaching, and even damage plant tissues, impacting yield potential. 
    • Plant adaptation:
      Different crop varieties have varying tolerance levels to light intensity, with some being better suited to high-light environments and others to low-light conditions. 
    Factors influencing light impact on crops:
    • Light quality:
      The specific wavelengths of light (blue, red, etc.) also affect plant growth, with certain wavelengths being more efficient for photosynthesis. 
    • Plant canopy structure:
      The density of leaves within a canopy can affect how much light reaches lower leaves, influencing their photosynthetic activity. 
    • Growing environment:
      Factors like greenhouse conditions, shade cloth, and planting density can be manipulated to optimize light exposure for plant growth.

Light intensity refers to the amount of light energy a plant receives. 


It significantly impacts plant growth in the following ways:

Effects of Light Intensity on Plants

  • Photosynthesis: Higher light intensity increases photosynthesis, leading to better plant growth and higher yield.
  • Leaf Development: Plants grown in low light have larger, thinner leaves, while those in high light develop smaller, thicker leaves.
  • Fruit and Flower Production: Many fruiting and flowering plants require high light intensity for better blooming and fruit set.
  • Stem Growth: Low light conditions result in elongated, weak stems (etiolation), whereas high light produces strong, compact plants.

Crop Responses to Light Intensity

  • High Light Crops: Tomato, pepper, citrus, and most fruit trees need full sunlight for maximum yield.
  • Medium Light Crops: Vegetables like lettuce, spinach, and cabbage can tolerate moderate light conditions.
  • Low Light Crops: Indoor plants like ferns, orchids, and snake plants thrive in shade or indirect light.

Managing Light Intensity in Horticulture

  • Greenhouses and Shade Nets: Used to control light levels for delicate crops.
  • Artificial Lighting: LED and fluorescent lights supplement light in controlled environments.
  • Pruning and Spacing: Helps optimize light penetration for better crop growth.