||The Root Zone
Introduction to the Root Zone
||Beneficials at the Root
Root Health and Pathogen
||Using good microbes to fight
the bad ones
||Keeping a Sterile Hydroponic
Root Rot and Pythium
||Bacteria Slime Molds and other
||What to do if
you have a bacterial or fungal infection
||Introduction to the Root Zone
Plant roots are arguably the most important part
of a plant, and are also one of the most easily damaged. Root problems
and disease are the most common source of problems for growers.
If you want to maximize the the health and ultimate yield of your
plants, it is wise to have a clear picture of the crucial activites
going on at the root zone.
Roots are made up of tough, fibrous tissues containing cellulose,
hemicellulose, and lignin which branch into the soil mass (or grow
media,) anchoring a plant firmly. Their basic functions are critical
for plant survival: they absorb water, oxygen and minerals, and
they conduct these to where they are needed. With a strong and healthy
root zone, plants are able to access what they need for vigourous
growth. Without a healthy root system, your plants are doomed to
be weak and spineless, or even worse, dead.
A healthy root zone is a continuously growing one. In many plants
this cycle includes the natural death of older roots and the production
of new ones. This cycle of death and regeneration is often mistaken
by growers as a sign of disease, but so long as there are new roots
developing, some root death should not be a concern.
Root Zone Health and Color
A young plant root system should have lots of white furry root tips
everwhere. A healthy mature root system will be strong and fiborous
and will have a thick root mat. If the roots are cream or yellow
on top of the mat, they should still have many white root tips underneath
at the bottom.
Thick, fat, white furry roots are what you most want to see - they
are absolutely indicative of healthy root growth. Be aware however
that the color of a nutrient solution will stain the roots, turning
them yellow or brown. This is also true of many nutrient additives.
Older, more mature plants will have a darker cream-colored root
system, and some plants just tend to have a natural color pigment.
Root Zone Temperature
The temperature of the root zone and the temperature of the nutrient
solution can have a major effect on the healthy growth and appearance
of the root system. In general the temperature should be between
68 and 72 degrees farenheit. Colder or warmer conditions can cause
poor and stunted root growth, as the roots don't want to grow into
the unhospitable nutrient solution. Major root death can occur in
even brief periods of cold or heat stress. Poor temperature conditions
leave the door open to root disease.
Oxygen at the Root Zone
Lack of oxygen at the root zone is the leading cause of root death.
Roots NEED oxygen. Roots should never sit in stagnant or ponding
nutrient solution - make sure the trays are tilted and supported
to drain completely. Lack of oxygen can also be caused by decomposing
organic material in the nutrient solution or trays - this material
should always be removed. . Another problem can be too many plants
competing for too little oxygen. These problems are worsened by
high root zone temperatures.
Nutrient reservoirs should always be aerated by and air pump and
air stone. You can never have too much oxygen, so the more and stronger
air pumps used, the better. We have had great succes adding air
stones to the growing trays themselves, to supplement the root zone
area with addtional oxygen. Some growers use H202 to add additional
oxygen, as well.
EC/ TDS & pH
A nutrient strength level that is too high can be toxic to the root
zone and will cause poor and stunted growth. At extreme levels,
a too high level will cause actual death in the root zone. It is
best to increase nutrient levels gradually over time rather than
suddenly and all at once.
||The root zone of a plant is buzzing with life-essential
processes of incredible complexity. This zone of intensive activity
is called the rhizosphere. The root itself makes up part of the rhizosphere
(the endorhizosphere), while the root hairs, mucigel, and root cells
that have sloughed off constitute the ectorhizosphere.
The plant actually grows its own garden of microbes, along the root
surfaces. To do this, the light energy captured from photosynthesis
in the leaves is channeled down the stem through the phloem vessels
and out through epidermal cells to the external root surface. Incredibly,
up to 80% of the total plant energy--but usually 12 to 40%--is exuded
as mucigel into the ectorhizosphere as carbohydrates, amino
acids, and other energy-rich compounds. As the roots grow, the roots
slough off dead cells which form a slimy covering and help the roots
to slide easily as they grow. This slime is a food source for many
millions of beneficial microbes. This food doesn't stay around long.
Billions of bacteria, fungi, algae, actinomycetes, protozoa, and other
microbes feed upon this exudate.
Those Phenomenal Mycorrhizae
Especially important are the mycorrhizal fungi which extend
their thread-like hyphae from inside cortex cells out into the soil
for several millimeters. They extend the feeding volume of the root
by 10 to 1,000 times or more for most plant species (the cabbage
family being a notable exception), and extract and carry nutrients
back to the root. So important are they that scientists sometimes
call the root zone the mycorrhizosphere. Pine trees will
hardly grow without these fungi. There are two types- ectomycorrhiza
and endomycorrhiza. Ectomycorrhiza are found in association with
forest trees such as pines, eucalyptus and dipterocarps, while endomycorrhizal
associations are formed in horticultural, forest and agronomic crops
Feeding On Exudate
In return for the release of nutritional substances from plant roots,
microbes themselves produce chemicals that stimulate plant growth
or protect the plant from attack. These substances include auxins,
enzymes, vitamins, amino acids, indoles and antibiotics. These complex
molecules are able to pass from the soil into plant cells and be
transported to other parts of the plant, with minimal change to
chemical structure, where they can stimulate plant growth and enhance
plant reproduction. They may also play a role in enhancing the nutritional
composition of the plant. The types of molecules released are specific
for a variety of plants grown under certain conditions, forming
in effect a unique chemical signature. As these molecules are released
into the rhizosphere, they serve as food and growth stimulants for
a certain mix of microbes.
The USDA Agricultural Research Service, and other scientists have
shown that for each plant species, this characteristic chemical
soup stimulates the development of a select, beneficial company
of root-dwelling microbes. This microbial population colonizes the
root zone, producing certain chemicals that inhibit the growth of
pathogenic species. These organisms are also instrumental in supplying
the plant’s unique nutritional needs .
The rhizosphere is always functioning for the plant whether it is
growing in a field, in a pot, in a hydroponic media, or even in
a lake or ocean. The details of function may differ somewhat, but
the principles are the same in order for the plant to survive.
||Some of the main Beneficials at the Root Zone
Several varieties of Bacillus (i.e Bacillus megaterium) have been
found to play a role in the conversion of unavailable forms of phosphates
into plant available forms. In natural settings they can provide
near 10% of the available phosphorous in the soil solution. With
increased levels of plant available phosphorous, Bacillus strains
become less effective. However, if the Bacillus can sustain as a
back up it may continue to provide hungry blooms with phosphorous
if it should become otherwise unavailable or “locked out”.
This bacterium is of special interest to organic farmers who incorporate
rock phosphate into the growing medium or if introduced through
fertilizer teas, preparations, etc. Rock phosphate tends to be mostly
unavailable, breaking down into plant available forms over time.
Certain forms of Bacillus are known to inhibit pythium and other
pathogens. One of these is bacillus subtilis and is found in
Mycorrhizal fungi are especially effective in providing nutrients
to plant roots. These are certain types of fungi that actually colonize
the outer cells of plant roots, but also extend long fungal threads,
or hyphae, far out into the rhizosphere, forming a critical link
between the plant roots and the soil. Mycorrhizae produce enzymes
that decompose organic matter, solubilize phosphorus and other nutrients
from inorganic rock, and convert nitrogen into plant available forms.
They also greatly expand the soil area from which the plant can
absorb water. In return for this activity, mycorrhizae obtain valuable
carbon and other nutrients from the plant roots. This is a win-win
mutualism between both partners, with the plant providing food for
the fungus and the fungus providing both nutrients and water to
the plant. The importance of mycorrhizae in plant productivity and
health has often been overlooked.It has been well documented that
mycorrhizal plants are often more competitive and better able to
tolerate environmental stress.Mycorrhizal technology has likewise
made possible the production of inoculants to significantly improve
the survival, growth and establishment of trees and crops.
M y•cor•rhi•zal - The symbiotic association of
the mycelium of a fungus with the roots of a seed plant.
Species of aerobic bacteria which converts ammonia to nitrite. One
of the critical bacteria in nitrogen cycle. Optimum pH range between
6.0 and 9.0, temperature 10oC - 34oC. Will acclimate to changes
in water quality, but activity is reduced during acclimation which
can lead to a build up of ammonia.
Nitrosomonas eat ammonia, they absolutely LOVE it. They Convert
plant available ammonium (NH4) to unavailable nitrite (NO2).
These bacteria convert the nitrite (NO2) resulting from the nitrification
above into nitrate (NO3-), an important form of Nitrogen that all
Bacteria that secrete a variety of compounds including antibiotics
that prevent and control root zone pathogens. A closely related
species of Streptomyces produces the antibiotic that we use, streptomycin.
Many studies demonstrate the bacteria’s effectiveness at controlling
root diseases, and select foliar diseases. An interesting consideration
noted in one study is that they will also reduce levels of some
nitrogen fixing bacteria in the soil.
Some species of fungi that parasitize other fungi, such as Trichoderma,
have been observed physically attacking and destroying pathogenic
fungi. Strains of Trichoderma are found naturally occurring in many
soils can play a role in the prevention and control of root pathogens,
ultimately providing a healthier soil environment which can lead
to higher yields. Some research suggests that the proteins in Trichoderma
can degrade chitin, which is a structural component found in pathogenic
fungi such as powdery mildew and in insects.
Some innovative propagation materials are inoculated with strains
of Trichoderma.Many forms of coco coir contain it naturally. CANNA's
Coco Growing Media is innoculated with it. If a healthy root
environment is maintained, the bacteria will continue to colonize
the roots and multiply in the growing media. The trichoderma help
to form a protective layer around the root system, helping to fend
off invading pathogens, etc.
||Root Health and Pathogen Control
In hydroponics we can promote a plant's rhizosphere
capability by insuring it has the proper minerals, as well as a
well aerated root zone to allow for good air and water movement
. We also suggest using an organic amendment like
Liquid Karma as well as a general enzymatic product like Hygrozyme
SensiZym from Advanced Nutrients that will encourage the proliferation
of healthy rhizosphere microbes. You may also wish to use a root
stimulator / stress reliever like CANNA
Rhizotonic. It is a powerful, organic stress-reliever which
stimulates new root development, increases resistance against disease
and improves the vigour of plants.
Most root pathogens seem to be opportunistic -that is, they take
advantage of weak and/or damaged roots. Thus the best defense is
to keep roots healthy in the first place. In the beginning of this
FAQ we went over some of the basics, those being temperature and
oxygenation. We can also add a silica to the nutrient solution such
Blast. Silica has been shown to greatly reduce plant death,
root decay and yield losses caused by root disease. It does this
by fortifying plant tissues against attack. The disease may still
be present, but it is not able to do damage.
It has been found by numerous studies that plant roots colonized
by a mixture of different bacterial and fungal species, are far
more resistant to pathogenic attack. Mycorrhizal fungi form an impenetrable
physical barrier on the surface of plant roots, varying in thickness,
density and fungal species, according to the plant species, plant
health and soil conditions. Ideally the beneficial microbes out-compete
pathogenic species and form a protective layer on the surface of
living plant roots. In soil it is usually only when the beneficial
species of bacteria and fungi are killed by continuous soil disturbance
and toxic chemicals that pathogenic species have an advantage.
||Using Good Microbes to fight the Bad Ones
There are a slew of new beneficial microbial products
on the market, and they have a variety of effects ranging from breaking
down nitrogen into useable forms to cleaning the roots to warding
off negative microbiological pathogens. These good microbes also
activate, enrich and stimulate the roots - they help to create beautiful
fuzzy white root growth like you have never seen before.
The new array of products on the market can be confusing an misleading.
We only sell products that we are familiar with and have personal
experience with. Here are some of what we think are best.
/ Earth Nectar: a two-part mycorrhizal fungi innoculant - in
to earth mycorrhizal root innoculant: in powdered form for soil
Piranha colonizes the root zone with 26 beneficial fungi (in
powder form for hydro)
Bacterial blend of 57 microorganisms, with 1.4 billion Colony Forming
Units per gram
juice Liquid solution consisting of five strains of bacterial
microbes, one is a nitrogen fixer
Hydroguard Water treatment and pathogen supressor made of four
benefical bacteria: Bacillus subtilis, Paenibacillus polymxa, Bacillus
circulans, and Bacillus amyloliquefaciens.
||The Other Route: Keeping the Reservoir Sterile
Some would argue that one of the strengths of hydroponics
is its sterile environment, and the notion of exposing growing systems
to bacterial and fungal organisms would be self-defeating, if not
sacrilegious. These growers rely on sterile growing environments,
strong disinfectants and a product like
SM-90. Another option is
Hydrogen Peroxide. Each of these offer their own protection
and benefits. But NEITHER SM-90 or Hydrogen Peroxide works well
with organic aditives in the reservoir. They do not work well together
and SM-90 has also been known to react poorly with Superthrive.
In a sterile growing environment, your goal is to have a super
clean reservoir. This is harder than it sounds. Folks who have been
growing in the same area with the same equipment for years might
find that they are suddenly having root problems when they never
had them before. Or a new grower might begin having problems right
from the beginning.
Keeping your reservoir totally sterile can work very well, but
once you get a population of icky badness it will keep coming back
again and again. Some pathogens such as pythium are almost impossible
to get rid of completelely. No matter how many times you sterilize
everything with a bleach solution, the problem returns. It can get
very frustrating and expensive to constanly be battling. More and
more innovative growers are moving toward a more wholistic approach
of using good microbes in the reservoir.
||Root Rot and Pythium
"Root rot" is a generic name for several
common opportunistic waterborne diseases that can seriously affect
indoor and outdoor crops year round. "Pythium" is the
name of one of these diseases and is also used as a generic term
for several different root rot and stem rot fungus species (including
Pythium, Verticillium, and Phytophthora, and Fusarium). The term
“damping-off” is also often used and usually applies
to disease in seeds, seedlings and clones.
Whatever you call them, these diseases attack the
roots of a plant and can rapidly infect crops in all stages. Damage
includes reduced yields and crop failure. Pythium is particularly
damaging in recirculating hydroponic systems as they provide ideal
conditions for rapid growth and spread of infectious spores; a single
infected plant can breed and send spores to all the plants.
The best thing is to prevent root rot from ever taking hold in the
first place. It is an opportunistic disease which means that it
is looking for sick, injured or weakened plants. Pythium is almost
impossible to 100% eradicate from an infected system; this involves
starting completely over (with new parents, containers, equipment,
etc). It is probably present even if you don't know it - just waiting
for its chance to get in.
“The best preventative measure against Pythium
attack is a healthy, rapidly growing plant as this is an opportunist
pathogen and will enter at the site of tissue injury or if the
plants are overly succulent, weakened or stressed for some reason.
Often root damage during the seedling stage as plants are introduced
to the hydroponic system is a danger time for Pythium infection.
Pythium is of greatest threat during the seed germination and
seedling development stage when plants are most vulnerable to
attack, and adequate control and elimination of the pathogen during
this stage is the best preventative measure of Pythium control
in hydroponic systems. Strong healthy plants will develop resistance
to Pythium attack during the seedling stage and this will prevent
problems at a later stage of growth. “
Dr. Lynette Morgan, Growing Edge Magazine
"Nutrient Temperature, Oxygen and Pythium in Hydroponics"t
How to Avoid a bad case of Root Rot
- Monitor plants and roots frequently
- Maintain a clean system – change and sterilize reservoir
- Design your system to combat pathogens
- keep your nutrient reservoir between 68 and 72F to maximize
root growth, Dissolved Oxygen levels and inhibition of Pythium.
80 degrees and above will bring on a fast case of root rot.
- Constant aeration – maintaining high dissolved oxygen
levels inhibits pathogens and accelerates root growth
- keep a lid on your reservoir to keep plant matter and light
- Maintain a low pH of 6.2 or less to inhibit pythium growth
- Use prevention!! Use tank additives to give your roots the
edge they need to grow strong and healthy!! Check out the
Roots and Prevention section.
||Bacterial slime and other horrifying nasties
||These are not the beneficial bacteria and fungi that
we have already spoken about. These bacteria cause cloudy reservoirs,
slimy build up, weird reservoir fuzz, gelatin growths and wild pH
fluctuations. These are the reservoir monsters.
When these bad microbes are present at high populations and are
happily feeding on organic matter, they use up just about all the
oxygen in the nutrient solution, suffocating the plants. They release
toxic substances as a biproduct of their life cycle. They also suppress
the good microbes at the root zone and cause problems with nutrient
uptake and plant growth.
Bacteria slime and cloudy reservoirs
Bacteria can make the water cloudy, but tend to produce more of
a slime or jellylike, smelly mass in the system.If you have it,
you will notice slimy reservoir walls and perhaps an oily slick
on the water. Another symptom can be a foamy buildup in the reservoir.
If left to their own devices, these bacterial growths will smother
the roots, depriving them of oxygen. Some species of anaerobic bacteria
thrive in an environment deprived of oxygen and can produce chemical
metabolites, such as alcohols, aldehydes, phenols and ethylene,
that are toxic to plant roots and to other microorganisms.
Other symptoms of bacterial infections can be fuzzy, cotton like
growths, or the growth of fur. Just in case you are wondering, that
white fuzzy growth you see at the tip of your roots is desireable.
That is not bacteria - That is the good stuff - you should see tiny
fine white hairs at thje roots.
All of these nasties require organic matter to feed on. They may
be there as the result of a buildup of dead roots and leaves in
the root zone, but usually they are the result of adding an organic
product to the reservoir. If the conditions are just right, the
bacteria will begin to thrive.
One option is to use no organic additives at all and to rely strictly
on chemical nutrients based on fertilizer salts. We think a better
choice is to continue using organic material, but also using an
enzymatic addtive like Hygrozyme
that will break down the unwanted organic matter in the reservoir
. If you would like to use additives such as bat guano, compost
or fish-based products, you might consider run to waste instead
of a recirculating system.
||What to do if you have a bacterial or fungal infection
You will want to completely clean out your system
- if you can, you should remove each plant, rinse it off, perhaps
even dip it in an H202 solution. You should trim off any dead roots.
you should then clean your entire system using a strong bleach or
h202 solution. We suggest soaking everything in bleach for a few
hours. You will definately want to soak your pump and any tubing
in bleach. Make sure you rinse everything very well before putting
the plants back in .
If your plants are damaged, you might want to run the nutrient solution
at a lower concentration than usual. We highly recommend using an
enzymatic addditive such as Hygrozyme.
. You should also run a stress relief additive like CANNA
Rhizotonic. We always suggest using
Liquid Karma , but if your problem is real bad, you might want
to lay off the organics a little bit.
While your roots are really hurting, you may want to foliar feed
your plants with Nitrozime
Master If you haven't already, you should read the section
above about inncoulating your system with good microbes.
Keep an eye on your reservoir. Be prepared to clean it out regularly,
as soon as any sign of a infections (cloudy water or wild pH fluctuations)
Remember IT IS MUCH EASIER TO PREVENT a pathogenic attack than
it is to ddeal with it once it has occured!