POWERING PHOTOSYNTHESIS
Light Stress
Plants’ photosynthetic
response to light varies
considerably between
species. Some plants
have evolved in shaded
conditions and need
much less light than
others. Many indoor plants
are in this category and can be
burned or damaged by use of highintensity lamps. Seedlings generally need
less light than mature plants and planting density also
determines how much output is needed from a light
source to reach light saturation and maximize yields.
Most commonly grown hydroponic vegetable and
flower crops become light saturated at around half the
light output of full sunlight, while some light-sensitive
plants may only need a fraction of this.
Growers soon become reasonably experienced at
picking up the signs of too much or too little light. Too
much light causes leaf burn, bleaching or scorching,
and plants become compact. Some species, such as
tomatoes and capsicums, may actually roll their outer
leaf margins inwards or point their leaf tips upwards
in an attempt to lower the amount of surface area
receiving the high light levels. Insufficient light often
Fruit flavor and
aroma is negatively
influenced by insufficient
lighting conditions.”
results in tall, spindly plants that stretch upwards,
becoming elon