Contributed by: Nietzsche
PLANT
ABUSEHeat
Stress : Look closely below, and you'll
see the brown leaf edges that are indicative of heat
stress. This damage looks alot like nutrient burn,
except it occurs only at the tops of the plants closest
to the lamps. There's only one cure for this...get the
heat away from the plants, either by moving the lamps or
moving the plants.
Figure 1
Nutrient Solution Burn:
There's a
good chance that this leaf was subjected to nutrient
solution burn. These symptoms are seen when the EC
concentration of hydroponic solutions is too high. These
symptoms also appear when strong nutrient solution is
splashed onto the leaves under hot HID lamps, causing
the leaves to burn under the solution.
Figure
2
Many hydroponic gardeners see this
problem. It's the beginning of nutrient burn. It
indicates that the plants have all the nutrients they
can possibly use, and there's a slight excess. Back off
the concentration of the nutrient solution just a touch,
and the problem should disappear. Note that if the
plants never get any worse than this leaf (figure 3),
then the plants are probably just fine. Figure 4 is
definitely an over-fert problem. The high level of
nutrients accumulates in the leaves and causes them to
dry out and burn up as shown here. You must flush with
clear, clean water immediately to allow the roots to
recover, and prevent further damage. Now find the cause
of the high nutrient levels.
Figure
3 (left) and Figure 4 (right)
Over Watering:
The plants in
figure 5 were on a continous drip system, where nutrient
solution is constantly being pumped into the medium.
This tends to keep the entire root system completely
saturated. A better way would be to periodically feed
the plants, say for 1/2 hour every 2-3 hours. This would
give the roots a chance to get needed air to them, and
prevent root rot and other problems.
Don't be throw
off by the fact that the plants in figure 5 are sitting
in still water, this is actually an H2O2 solution used
to try and correct the problem. Adding an airstone to
the tub would also help add O2 to the solution.
Figure
5
pH
Fluctuation:
Both of these leaves in
figure 6 and figure 7 are from the same plant. It could
be over fertilization, but more likely it is due to the
pH being off. Too high or too low a pH can lock up
nutrients in the form of undisolvable salts and
compounds, some of which are actually toxic to the
plants. What then happens is the grower then tries to
supplement the plants diet by adding more fertilizers,
throwing off the pH even more and locking up even more
nutrients. This type of problem is seen more often in
soil mixes, where inconsistent mixing of the medium's
components leads to "hot" spots.
Figure
6 (left) and Figure 7 (right)
Ozone Damage:
Ozone damage
typically found near the generator. Although a rare
problem, symptoms generally appear as a Mg deficiency,
but the symptoms are localized to immediately around the
generator.
Figure
8
NUTRIENT
PROBLEMS
Root
Stunting:
Root stunting is characteristic
of calcium deficiency, acidity, aluminum toxicity, and
copper toxicity. Some species may also show it when
boron deficient. The shortened roots become thickened,
the laterals become stubby, peg-like, and the whole
system often discolours, brown or grey.
Symptoms
localized at shoot growing points.
New shoots
unopened; young leaves distorted; dead leaf tips; pale
green plant copper deficiency
New shoots withered or
dead; petiole or stem collapse; shoots stunted; green
plant calcium deficiency Young leaves pale green or
yellow; rosetting or dead tip; dieback; dark green plant
boron deficiency
MOBILE
ELEMENTS
Mobile elements are more likely
to exhibit visual deficiencies in the older leaves,
because during demand these elements will be exported to
the new growth.
Nitrogen
(N)
Nitrate - Ammonium is found in both
inorganic and organic forms in the plant, and combines
with carbon, hydrogen, oxygen and sometimes sulfur to
form amino acids, amino enzymes, nucleic acids,
chlorophyll, alkaloids, and purine bases. Nitrogen rates
high as molecular weight proteins in plant tissue.
Plants need lots of N during vegging, but it's easy
to overdo it. Added too much? Flush the soil with plain
water. Soluble nitrogen (especially nitrate) is the form
that's the most quickly available to the roots, while
insoluble N (like urea) first needs to be broken down by
microbes in the soil before the roots can absorb it.
Avoid excessive ammonium nitrogen, which can interfere
with other nutrients.
Too much N delays flowering.
Plants should be allowed to become N-deficient late in
flowering for best flavor.
Nitrogen
Deficiencies:
Plants will exhibit lack of vigor,
slow growth and will be weak and stunted. Quality and
yield will be significantly reduced. Older leaves become
yellow (chlorotic) from lack of chlorophyll. Deficient
plants will exhibit uniform light green to yellow on
older leaves, these leaves may die and drop. Leaf
margins will not curled up noticeably. Chlorosis will
eventually spread throughout the plant. Stems, petioles
and lower leaf surfaces may turn purple.
Figure
9
As seen in figure 10 consumption
of nitrogen (N) from the fan leaves during the final
phase of flowing is 100% normal.
Figure
10
Nitrogen Toxicity:
Leaves are often dark green and in the early stages
abundant with foliage. If excess is severe, leaves will
dry and begin to fall off. Root system will remain under
developed or deteriorate after time. Fruit and flower
set will be inhibited or deformed.
With breakdown of
vascular tissue restricting water uptake. Stress
resistance is drastically diminished.
Phosphorus (P)
Phosphorus is a
component of certain enzymes and proteins, adenosine
triphosphate (ATP), ribonucleic acids (RNA),
deoxyribonucleic acids (DNA) and phytin. ATP is involved
in various energy transfer reactions, and RNA and DNA
are components of genetic information.
Phosphorus (P) deficiency:
Figure 11
is severe phosphorus (P) deficiency during flowering.
Fan leaves are dark green or red/purple, and may turn
yellow. Leaves may curl under, go brown and die.
Small-formed buds are another main symptom.
Phosphorus deficiencies exhibit slow growing, weak
and stunted plants with dark green or purple
pigmentation in older leaves and stems.
Some
deficiency during flowering is normal, but too much
shouldn't be tolerated. Red petioles and stems are a
normal, genetic characteristic for many varieties, plus
it can also be a co-symptom of N, K, and
Mg-deficiencies, so red stems are not a foolproof sign
of P-deficiency. Too much P can lead to iron deficiency.
Purpling: accumulation of anthocyanin pigments;
causes an overall dark green color with a purple, red,
or blue tint, and is the common sign of phosphate
deficiency. Some plant species and varieties respond to
phosphate deficiency by yellowing instead of purpling.
Purpling is natural to some healthy ornamentals.
Figure
11
Figure 12 shows Phosphorus (P)
deficiency during vegatative growth. Many people
mistaken this for a fungus, but look for the damage to
occur near the end of leave, and leaves the color dull
greyish with a very brittle texture.
Figure
12
Phosphorus (P)
Toxicity:
This condition is rare and usually
buffered by pH limitations. Excess phosphorus can
interfere with the availability and stability of copper
and zinc.
Potassium
(K)
Potassium is involved in maintaining
the water status of the plant and the
tugor pressure
of it's cells and the opening and closing of the
stomata. Potassium is required in the accumulation and
translocation of carbohydrates. Lack of potassium will
reduce yield and quality.
Potassium
deficiency:
Older leaves are initially chlorotic
but soon develop dark necrotic lesions
(dead
tissue). First apparent on the tips and margins of the
leaves. Stem and branches may become weak and easily
broken, the plant may also stretch. The plant will
become susceptible to disease and toxicity. In addition
to appearing to look like iron deficiency, the tips of
the leaves curl and the edges burn and die.
Potassium - Too much sodium (Na) displaces K,
causing a K deficiency. Sources of high salinity are:
baking soda (sodium bicarbonate "pH-up"), too much
manure, and the use of water-softening filters (which
should not be used). If the problem is Na, flush the
soil. K can get locked up from too much Ca or ammonium
nitrogen, and possibly cold weather.
Figure
13
Figure 14
Potassium (K)
Toxicity:
Usually not absorbed excessively by
plants. Excess potassium can aggravate the uptake of
magnesium, manganese, zinc and iron and effect the
availability of calcium.
Magnesium (Mg)
Magnesium is a
component of the chlorophyll molecule and serves as a
cofactor in most enzymes.
Magnesium (Mg)
deficiency:
Magnesium deficiency will exhibit a
yellowing (which may turn brown) and interveinal
chlorosis beginning in the older leaves. The older
leaves will be the first to develop interveinal
chlorosis. Starting at leaf margin or tip and
progressing inward between the veins. Notice how the
veins remain somewhat green though as can be seen in
figure 15.
Notice how in figure 16 and 17 the leaves
curl upwards like they're praying? They're praying for
Mg! The tips may also twist.
This can be quickly
resolved by watering with 1 tablespoon Epsom
salts/gallon of water. Until you can correct nutrient
lockout, try foliar feeding. That way the plants get all
the nitrogen and Mg they need. The plants can be foliar
feed at teaspoon/quart of Epsom salts (first powdered
and dissolved in some hot water). When mixing up soil,
use 2 teaspoon dolomite lime per gallon of soil.
If
the starting water is above 200 ppm, that is pretty hard
water, that will lock out mg with all of the calcium in
the water. Either add a 1/4 teaspoon per gallon of epsom
salts or lime (both will effectively reduce the lockout
or invest into a reverse osmosis water filter.
Mg
can get locked-up by too much Ca, Cl or ammonium
nitrogen. Don't overdo Mg or you'll lock up other
nutrients.
Figure
15
Figure 16
Figure
17
Magnesium (Mg) Toxicity:
Magnesium toxicity is rare and not generally
exhibited visibly. Extreme high levels will antagonize
other ions in the nutrient solution.
Zinc (Zn)
Zinc plays a roll in the
same enzyme functions as manganese and magnesium. More
than eighty enzymes contain tightly bound zinc essential
for their function. Zinc participates in chlorophyll
formation and helps prevent chlorophyll destruction.
Carbonic anhydrate has been found to be specifically
activated by zinc.
Zinc Deficiencies:
Deficiencies appear as chlorosis in the inter-veinal
areas of new leaves producing a banding appearance as
seen in figure 18. This may be accompany reduction of
leaf size and a shortening between internodes. Leaf
margins are often distorted or wrinkled. Branch
terminals of fruit will die back in severe cases.
Also gets locked out due to high pH. Zn, Fe, and Mn
deficiencies often occur together, and are usually from
a high pH. Don't overdo the micro-nutrients, lower the
pH if that's the problem so the nutrients become
available. Foliar feed if the plant looks real bad. Use
chelated zinc. Zinc deficiency produces "little leaf" in
many species, especially woody ones; the younger leaves
are distinctly smaller than normal. Zinc defeciency may
also produce "rosetting"; the stem fails to elongate
behind the growing tip, so that the terminal leaves
become tightly bunched.
Figure
18
Zinc Toxicity:
Excess
Zinc is extremely toxic and will cause rapid death.
Excess zinc interferes with iron causing chlorosis from
iron deficiency. Excess will cause sensitive plants to
become chlorotic.
IMMOBILE
ELEMENTS
Immobile elements will show
their first symptoms on younger leaves and progress to
the whole plant.
Sulphur
(S)
Sulfate is involved in protein
synthesis and is part of the amino acids, cystine and
thiamine, which are the building blocks of proteins. It
is active in the structure and metabolism in the plant.
It is essential for respiration and the synthesis and
breakdown of fatty acids.
Sulphur (S)
deficiency:
The initial symptoms are the
yellowing of the entire leaf including veins usually
starting with the younger leaves. Leaf tips may yellow
and curl downward. Sulfur deficiencies are light green
fruit or younger leaves with a lack of succulence.
Elongated roots and woody stem. Although it's hard to
see in figure 19, the upper stems of this plant are
purple. Although many varieties of cannabis do get
purplish stems, the trait generally extends the entire
length of the plant's stem, and not just near the top as
in this specimen.
Figure
19
Sulphur Toxicity:
Leaf
size will be reduced and overall growth will be stunted.
Leaves yellowing or scorched at edges. Excess may cause
early senescence.
Calcium
(Ca)
Calcium plays an important role in
maintaining cell integrity and membrane permeability.
Calcium Deficiency:
Young leaves are
affected first and become small and distorted or
chlorotic with irregular margins, spotting or necrotic
areas. Bud development is inhibited, blossom end rot and
internal decay may also occur and root may be under
developed or die back. Deficiency will cause leaf tip
die-back, leaf tip curl and marginal necrosis and
chlorosis primarily in younger leaves. Symptoms: young
leaves develop chlorosis and distortion such as
crinkling, dwarfing, developing a strap-like shape,
shoots stop growing and thicken.
Calcium
Toxicity:
Difficult to distinguish visually. May
precipitate with sulfur in solution and cause clouding
or residue in tank. Excess calcium may produce
deficiencies in magnesium and potassium.
Iron (Fe)
Iron is
an important component of plant enzyme systems for
electron transport to carry electrons during
photosynthesis and terminal respiration. It is a
catalyst for chlorophyll production and is required for
nitrate and sulfate reduction and assimilation.
Iron deficiency:
- Pronounced
interveinal chlorosis similar to that caused by
magnesium deficiency but on the younger leaves.
-Leaves exhibit chlorosis (yellowing) of the
leaves mainly between the veins, starting with the lower
and middle leaves.
Caused by factors that
interfere with iron absorption of roots: over
irrigation, excessive soluble salts, inadequate
drainage, pests, high substrate pH, or nematodes. This
is easily corrected by adding an iron supplement with
the next watering.
Fe is unavailable to plants
when the pH of the water or soil is too high. If
deficient, lower the pH to about 6.5 (for rockwool,
about 5.7), and check that you're not adding too much P,
which can lock up Fe. Use iron that's chelated for
maximum availability. Read your fertilizer's ingredients
- chelated iron might read something like "iron EDTA".
To much Fe without adding enough P can cause a
P-deficiency.
Note : When adding iron to the
solution, it is often necessary to not use fertilizer
for that watering. Iron has a tendency of reacting with
many of the components of fertilizer solutions, and will
cause nutrient lockup to occur. Read the labels of both
the iron supplement and the fertilizer you are using
before you attempt to combine the two.
Figure
20
Iron Toxicity:
Excess
accumulation is rare but could cause bronzing or tiny
brown spots on leaf surface.
Manganese (Mn)
Manganese is
involved in the oxidation reduction process in the
photosynthetic electron transport system. Biochemical
research shows that this element plays a structural role
in the chloroplast membrane system, and also activates
numerous enzymes.
Manganese Deficiency:
Interveinal chlorosis of younger leaves, necrotic
lesions and leaf shredding are typical symptom of this
deficiency. High levels can cause uneven distribution of
chlorophyll resulting in blotchy appearance. Restricted
growth and failure to mature normally can also result.
-Mn gets locked out when the pH is too high,
and when there's too much iron. Use chelated Mn.
Manganese Toxicity:
Toxicity:Chlorosis, or
blotchy leaf tissue due to insufficient chlorophyll
synthesis. Growth rate will slow and vigor will decline.
Chlorine (Cl)
Chloride is involved in
the evolution of oxygen in the photosynthesis process
and is essential for cell division in roots and leaves.
Chlorine raises the cell osmotic pressure and affects
stomata regulation and increases the hydration of plant
tissue. Levels less than 140 ppm are safe for most
plants. Chloride sensitive plants may experience tip or
marginal leaf burn at concentrations above 20 ppm.
Chlorine Deficiency:
Wilted chlorotic leaves
become bronze in color. Roots become stunted and
thickened near tips. Plants with chlorine deficiencies
will be pale and suffer wilting.
Chlorine Toxicity:
Burning of leaf tip or margins. Bronzing, yellowing
and leaf splitting. Reduced leaf size and lower growth
rate.
Boron (B)
Boron biochemical
functions are yet uncertain, but evidence suggests it is
involved in the synthesis of one of the bases for
nucleic acid (RNA uracil) formation. It may also be
involved in some cellular activities such as division,
differentiation, maturation and respiration. It is
associated with pollen germination.
Boron
Deficiency:
Plants deficient in boron exhibit
brittle abnormal growth at shoot tips and one of the
earliest symptoms is failure of root tips to elongate
normally. Stem and root apical meristems often die. Root
tips often become swollen and discolored. Internal
tissues may rot and become host to fungal disease.
Leaves show various symptoms which include drying,
thickening, distorting, wilting, and chlorotic or
necrotic spotting.
Boron Toxicity:
Yellowing of
leaf tip followed by necrosis of the leaves beginning at
tips or margins and progressing inward before leaves die
and prematurely fall off. Some plants are especially
sensitive to boron accumulation.
Copper
(Cu)
Copper is a constituent of many enzymes and
proteins. Assists in carbohydrate metabolism, nitrogen
fixation and in the process of oxygen reduction.
Copper Deficiency:
Symptoms of deficiency are a
reduced or stunted growth with a distortion of the
younger leaves and growth tip die-back. Young leaves
often become dark green and twisted. They may die back
or just exhibit necrotic spots. Growth and yield will be
deficient as well.
Copper Toxicity:
Copper is
required in very small amounts and readily becomes toxic
in solution culture if not carefully controlled. Excess
values will induce iron deficiency. Root growth will be
suppressed followed by symptoms of iron chlorosis,
stunting, reduced branching, abnormal darkening and
thickening of roots.
Molybdenum (Mo)
Molybdenum is a component of two major enzyme
systems involved in the nitrate reeducates, this is the
process of conversion of nitrate to ammonium.
Molybdenum Deficiencies:
Often interveinal
chlorosis which occurs first on older leaves, then
progressing to the entire plant. Developing severely
twisted younger leaves which eventually die. Molybdenum
deficiencies frequently resemble nitrogen, with older
leaves chlorotic with rolled margins and stunted growth.
Molybdenum Toxicity:
Excess may cause
discoloration of leaves depending on plant species. This
condition is rare but could occur from accumulation by
continuous application. Used by the plant in very small
quantities. Excess mostly usually does not effect the
plant, however the consumption of high levels by grazing
animals can pose problems so she might not be too good
to smoke.
Sodium (Na)
Sodium seems to
encourage crop yields and in specific cases it acts as
an antidoting agent against various toxic salts. It may
act as a partial substitute for potassium deficiencies.
Excess may cause plant toxicity or induce deficiencies
of other elements. If sodium predominates in the
solution calcium and magnesium may be affected.
Silicon (Si)
Silicon usually exists
in solution as silicic acid and is absorbed in this
form. It accumulates as hydrated amorphous silica most
abundantly in walls of epidermal cells, but also in
primary and secondary walls of other cells. It is
largely available in soils and is found in water as
well. Inadequate amounts of silicon can reduce tomato
yields as much as 50%, cause new leaves to be deformed
and inhibit fruit set. At this time toxicity symptoms
are undetermined.
Cobalt (Co)
Cobalt is essential to many
beneficial bacteria that are involved in nitrogen
fixation of legumes. It is a component of vitamin B12
which is essential to most animals and possibly in
plants. Reports suggest that it may be involved with
enzymes needed to form aromatic compounds. Otherwise, it
is not understood fully as to its benefit to plant
growth, but it is considered essential to some animal
health issues.
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