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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