Growth in Plants
Every plant species has particular conditions where they will
flourish. There are various physical factors that affect
the growth rate of plants; however, all plants share one universal
growth limiting factor. Minimally stated it is "the
rate of any growth process controlled by 2 or more factors
is limited by the factor in least supply". In layman's
terms, the chain of growth is only as strong as the weakest
Basic Factors Affecting Plant Growth
There are seven (7) fundamental factors that have the potential
to limit or assist in the growth of a plant. These seven
factors are listed below:
- pH Level - The acid/alkaline levels in soil, growth medium,
nutrient solution etc.
- Light - Intensity, color and photoperiod or length of
- Atmosphere - Some sub-factors are oxygen, carbon dioxide
- Nutrients or Soluble Minerals - Found in the soil or hydroponic
- Temperature - Both of the air and the root zone. Also,
the variation between the high and low temperature plays
a part in growth or lack thereof.
- Soil or Hydroponic Growing Media Particle Size - The size
affects the rate of drainage as well as aeration or oxygen
content at the root zone
- Water - Will effect all other factors and all other factors
can effect water.
With that said, what are the optimal conditions for growing
For most plant life, the most favorable pH value is between
6 - 6.8. This is not something that should consume one's
time as the pH level of the hydroponic solution will change
from night to day and even hour to hour. This is caused
by plants taking in the nutrients and then emitting carbon
dioxide at night. As long as the pH level maintained
in the system is between 5.8 and 6.8 it will not limit the
growth of the most plants.
In the summer when the sun is the brightest and plants reside
outside or in a greenhouse, sunlight is generally not a limiting
factor. However, some plants do require partial shade
to grow best.
In regards to hydroponic systems where light may not be as
as strong, light may be limiting factor. One may want
to employ a light meter and consult a horticulture book to
measure and learn the minimum footcandles for the species
in the crop.
The blue and red portions of the light spectrum are most
efficient in producing plant growth. The red spectrum
may also stimulate the flowering response in various plants.
Some plants also have precise photoperiod needs, to stimulate
flowering, like the Chrysanthemums.
Carbon dioxide and humidity are the two most influential sub-factors
in the atmosphere category.
Typically, humidity is not likely to be a limiting factor.
If the air increases in humidity, then increased ventilation
must be provided. For every 10 degrees Fahrenheit rise
in temperature, the air will hold twice the moisture.
Relative humidity from 40 to 60% is beneficial for most plants.
For plants that have enough warmth, light and nutrients,
the likely growth limiting factor will be carbon dioxide.
The most advantageous growth temperature for many species
will increase if sufficient carbon dioxide is available. Outside
air contains about 300 PPM of Carbon dioxide. Though,
with all other factors being available in adequate measure
the best carbon dioxide level may be between 2500 PPM and
4000 PPM. PLEASE NOTE: Carbon dioxide levels over 2500
PPM are toxic to humans.
As mentioned previously there are two temperature zones that
one must be aware of in a hydroponic system: Air and Root.
The most favorable air temperature for most plant species
is between 65-85 degrees Fahrenheit. If the air temperature
is in excess of the range, it places stress on the water and
nutrient uptake system of the plant. Below 60 degrees
Fahrenheit plant growth will be stunted considerably.
The root zone temperature is an entirely separate concern.
The optimum is about 70 to 75 degrees Fahrenheit. This
allows maximum nutrient and water intake.
Nutrients, also dubbed "plant food", are soluble
minerals that, when mixed with water, allow the plant to feed.
Needed nutrients fall into two categories: Macro and Micro
Macro elements are vital to plant health; these include:
Other elements needed are called Micro elements. Included
in this category are:
It is important to note that some of the Micro elements are
toxic to the plant at levels as low as 0.01 PPM.
The total strength of the solution usually ranges from 500
to 3500 PPM. There is a wide variation here as it widely
depends on the plant species and temperature. For most
plants, a solution strength of 1000 PPM to 2000 PPM facilitates
growth best. A note of caution: use a lower solution
strength in very hot climates.
Nutrients are only absorbed if oxygen is readily available
at the root zone. The optimum dissolved oxygen content
of the nutrient solutions 6 PPM at 70 - 75 degrees Fahrenheit.
This is realized by continual aeration of the solution.
The best media particle size is usually between 3 to 8 mm.
This permits rapid drainage while allowing fresh air to be
drawn into the root zone. The growing media should also
be inert, to prevent interactions with the nutrient solution.
The capillary action of the media also affects the optimum
size. For example, Rock wool has 0.005 mm fibers with
96% pore space. This works extremely well as it is porous
and allows for drainage and aeration.
Through the products provided by High Nutrients, you may
be able to elude many of the factors that will limit the growth
of a given crop.
Carbo-Load plant sugar supplement