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downward may lose up to 40% of the light.

instead, tubes are mounted onto a reflector with individual baffles between the tubes so

that light is directed downward to the garden. A good reflector may keep losses down to

20%. An alternative is to use tubes with reflective surfaces. These are made several

manufacturers. Often stores do not carry them but will special order thern. New

fluorescent corfigurations have made it easier to build a garden. Circle tubes and thin

tubed 8" doubles screw into incandescent sockets. Although these bulbs are not very

efficient they are step up from incandescents. Combinations of circle lights and tubes can

illuminate a garden very brightly. They can be used in extremely small spaces. These lamps

always seem to be on sale. When electrical costs are not a factor they are a inexpensive

way of setting up a garden. As tubes age they become less efficient. On the average, they

lose 25% of light theywere rated for after about a year of use. Lights which are turned on

and off a lot wear out faster. Three to six inch sections on both sides of the tube dull

out from deposits after a short term of use. Growers figure the effective length of a 4 ft

tube as 3 feet 4 inches and of an 8 ft tube as 7 feet. Light Spectrums and photosynthesis

Each source of light has a characteristic spectrum, which is caused by the varying wave

lengths of light therein. Fluorescents and other electric lights emit different shades of

light. To our eyes mid-day summer sunlight looks neutral, incandescent lights have a

reddish tint, fluorescents vary in spectrum according to their type, MH lamps a have a

blue coolness to them and HPS lamps look pink-amber. To produce chiorophyll, plants need

light from specffic spectrums, mainly red and blue. This is called the chloroplast light

spectrum. Once the chlorophyll is produced, a slightly different spectrum of light is used

by the plant fur photosynthesis, the process which results in the production of sugars.

Plants use red and blue light most efficiently but they also use use orange and yellow

light. Plants are continually growing producing new chioroplasts and chlorophyll so both

spectrums of light are being used by the plant continually. Plants reflect green light

rather than using it. Although the MH and HPS lamps emit different color light both lamps

emit high levels of light in the critical red and blue wavelengths. Either lamp can be

used for cultivation. HPS lamps produce faster growth because they emit more total light

useable by the plant. Many shop owners maintain that combinations of MH and HPS lights

produce the fastest growth, or alternatively, that MH units should be used for growth and

HPS units for flowering. There is no indication that either of these theories holds up.

HPS lamps produce faster growth than a comm bination of HPS and MH lamps. There is

absolutely no need to or advantage to buying a MH unit. Plants grown under HPS show some

stem etoliation (stretching) and ripen about aweek later. This is more than compensated

with a considerably larger crop. Some fluorescent tube manufacturers produce grow tubes

which are especially formulated to provide a spectrum of light similar to the chlorcphyll

synthesis or photosynthesis spectrum or a compromise between thern. The idea is sound, but

grow tubes produce only 35-60% of the light of a cool white fluorescent, and less light

useable by the plant. One manufacturer advertises Vita-Lite and Optima fluorescent tubes

which emit a light spectrum color balanced close to the sun's spectrum. However, they emit

only 75% of the light of a warm white fluorescent. COSTS HPS systems are the most

expensive to purchase of all of the lighting units. MH units area little cheaper and

fluorescents are the cheapest of alL However, this is figuring only the intial outlay.

Factoring in the cost per unit of light produced, the positions are reversed. HPS lamps

are the cheapest, followed by MH lamps and far behind come the fluorescents. In addition

HID lamps are considered easier to work with in the garden and produce a better crop than

fluorescents. Cost In cents per 1000 lumens of various lamps. (Expressed in cents per

kilowatt) In dollar terms the figures for a 1000 HPS are $0006, $0007, $0008, $0011 Step

By Step 1. The successful gardens I have observed use a minimum of 1000 lumens per sq. ft

during vegetative growth and 1,500 lumens during flowering These figures are bare

minimums, the more light the better. Gardens with 1500-2500 lumens during vegetative

growth and 2000-3500 during flowering seem to do best. 2. The most efficient light source

is a HPS lamp in a horizontal reflector. No other light source is needed. An HPS lamp

supplies all the spectrums of light needed by the plant for normal growth. Both

fluorescent fixtures and HID lamps use a much higher voltage of electricity than standard

110 volt house current. Fluorescent fixtures contain a ballast or transfurmer that

converts electricity to its proper voltage. HID lamps sometimes come in a fitting

containing the ballast. but most of the units made for indoor gardens are designed with

the ballast remote (separate, but connected by an electrical cord) from the lamp and

reflector. HID's with remote ballasts are much more convenient than units with the

ballasts enclosed since they weigh less. 400 watt ballasts weigh about 28 lbs. and 1000

watt ballasts weigh about 40 lbs. it is much harder to manipulate and secure a heavy

object like that overhead than it is to just leave it near ground level attached to the

lamp by an electrical cord. The lamp is hung from the ceiling using cord or wire attached

to a hook or pulley Light Movers Outdoors, plants receive light from many directions. Over

the course of the day the sun bathes plants in light starting in the east and travelling

west. leaves shaded during part of the day are under full sun at other times. Indoors,

using a stationary light. some plant parts are always shaded while others are always lit.

With a light in the center of the garden, plants closer to the source receive brighter

light than those at the periphery. Reflectors with different shapes distribute light in

varying patterns. A good quality reflector will spread the light evenly over the garden.

Still, a light coming from a single stationary source leaves some areas in permanent

shadow. Light movers were invented to solve these problems. The movers carry the lamp over

a fixed course so that entire the garden comes direcdy under the light part of the time.

These units are manufactured by a number ofsuppliers and use several innovative techhiques

to move the lamps. Some of them move the lamps quickly, so that the light passes over the

garden in less than a minute. Other movers take 40 minutes to traverse the course. Both

types improve light distribution in the garden. As a result, the plants grow at an even

rate. Since the plants are not stretching in one direction to the light, they grow

straighter, with more symetry. The rotating units seem most effective in a square room,

while the shuttles, which go back and forth, seem best in rectangular or odd shaped

spaces. REFLECTIVE MATERIAL Closet cultivators have found that electrically generated

light is precious so any generated is best conserved. Efficient indoor gardens must

reflect back the light straying out of the perimeter. Growers cover walls which cannot be

painted with flat white paint, with aluminum foil, Astrolon or mylar. This is extremely

important. Any light which hits a dark surface is absorbed and converted into heat, rather

than being used in the garden. Reflective material is easily hung using staples tacks or

tape. There are several ways growers make walls very reflective: White reflective paint.

Flat white paint defracts the light so that it is distributed more evenly through the

garden. Off.whites absorb a considerable amount of light so they are avoided. The best

paint for indoor gardens is greenhouse white which is formulated for maximum reflectivity.

Aluminum foil is used to line the walls. It is highly reflective and very inexpensive. Its

downsides are that is noisy when it moves with a breeze and has little tensile strength,

so that it tears easily when not attached to a surface. It is usually not used where it

will be moved around or used for a curtain or doorway because it crinkles and tears

easily. When the dull side out is used the reflection is defused rather than just

reflecting hot spots. Eighteen inch wide heavy duty rolls are the easiest to work with. In

places where heat must be conserved fiberglass insulation with aluminum reflective surface

is often used to line the walls. Silvered gift wrap comes in rolls or sheets. It is

composed of a thin metal foil glued onto paper wrap. It is very reflective, easy to use

and inexpensive. It is available from some wholesale gift paper houses or from gift shops.

Styrofoam is used in cool spaces where heat must be conserved. The walls can be lined with

styrofoam insulating material which comes on a roll or in sheets. (available in some

home-improvement stores). It is extremely reflective. The rolls come in several widths,

and is about 1/8" thick Mylar. Grow stores sell silvered mylar which is extremely

reflective. While mylar reflects most of the light, it is not opaque and it allows a dim

image through. The plastic film creases easily. Astrolon is a silvered plastic which is

extremely reflective, but not opaque. The thin plastic is quilted and very pliable. It is

very durable and very reflective. Step by Step 1. Successful closet cultivators know that

light should be distributed evenly throughout the grow space. light movers or several

lights may be indicated. 2. Smart growers line the walls of the growing area with a

reflective surface to conserve light. FOOD To keep plants alive and healthy, a grower

needs facts about plant nutrition. This chapter lists all the nutrients a marijuana plant

requires Although many elements are present in cannabis tissues, we will discuss only the

essential ones: those necessary for the plant to complete the vegetative, or reproductive,

phases of its life cycle. Along with hydrogen, carbon, and oxygen, the six other essential

elements, or macronutrients, that are present in the greatest quantities in plants are

nitrogen, phosphorus, potassium, calcium, sulfur, and magnesium. Eight other essential

elements required in smaller amounts (micronutrients) are iron, boron, manganese, copper,

molybdenum, chlorine, zinc, and cobalt. The physiological functions of these elements, as

well as the general visible symptorns of deficiencies of the same elements, are given on

the following pages. Nitrogen Function: Development of chlorophyll. Promotes stem and

fruit growth. Increases protein synthesis. Occurs in amino acids, nucleic acids, enzymes,

coenzymes, membranes and other constituents of plant life. Deficiency: In young plants,

stunted growth and yellowish green leaves. Bottom leaves appear light green, followed by

yellowing, drying, and shedding, with purplish red pigments in veins. Stems are short and

thin; growth is upright and spindly; flowering is reduced. Phosphorus Function: Stimulates

early root formation. Hastens maturity. Stimulates blooming. Plays a major role in the

production of ATP (adenosine triphosphate), a plant energy source. Also found in nucleic

acids, fats, coenzymes, and sugar phosphates. Deficiency: Young plants stunted, leaves

dark blue-green, sometimes purplish. Stems thin; veins may show signs of necrosis

(blackening and decay of tissues). Plants often dwarf at maturity. Potassium Function:

Necessary to the formation and transfer of starches, sugars, and oils in the plant. Needed

as a cofactor for more than forty enzymes. Performs a vital function in the stomatal

movements. (Stomates are structures, found on the leaves, which allow for the exchange of

gases and water vapor with the air.) Improves seed quality. Deficiency: Leaves usually

dark blue-green with marginal chlorosis (failure to produce normal amounts of

chlorophyll). Necrosis, appearing first on bottom leaves; a wrinkled or corrugated

appearance between the veins. Calcium Function: Influences absorption of plant nutrients.

Neutralizes acidic conditions. Neutralizes toxic compounds produced in the plants.

Necessary for the development of roots. Component of cell walls. Needed as a coenzyme for

the breakdown of ATI and phospholipids. Deficiency: Leaves chlorotic, rolled, curled.

Break-down of growing tissues in the stem and roots. Roots poorly developed and may appear

gelatinous. Sulfur Function: Component of amino acids, some fats, proteins, enzymes,

coenzymes, and other cellular compounds. Deficiency: Leaves light green to yellow in

color, starting along the veins of the top leaves. Thin stems. Magnesium Function:

Necessary for a large number of enzymes involved in phosphate transfer. Component of the

chlorophyll molecule. Deficiency: Spotted chlorosis with veins green and leaf web tissue

yellow or white, appearing first on the bottom leaves. In severe cases the leaves may wilt

and shed; brittleness is common; necrosis usually occurs. Micronutnents Iron Function:

Occurs in many of the respiratory enzymes and activates others. Deficiency: White

chlorosis between the veins in the leaves, first on the bottom leaves, often becoming

necrotic; leaves may become completely white with brown margins and tips. Boron Function:

Involved in carbohydrate transport. Necessary for root development. Reduces oxygen uptake

by ground leaf tissue. Deficiency: Top leaves necrotic, shed; growing tissues break down

and may become necrotic; roots short and stunted; flowering reduced. Manganese Function:

Required for the activity of enzymes in photosynthetic production of oxygen. Deficiency:

Spotted chlorosis with leaf web tissue yellow or white, appearing first on the top leaves.

Stems yellow, often woody. Copper Function: Found in some enzymes, activates others,

particularly those enzymes connected with respiration and the chloroplasts. Deficiency:

Wilting of the top leaves, often followed by death; chlorophyll and other pigments

reduced. Molybdenum Function: Necessary to enzymes and for the breakdown of nitrogen.

Deficiency: Light yellow chlorosis; leaves may fail to develop. Chlorine Function:

Involved in the photosynthetic reactions for the release of oxygen. Deficiency: Wilting of

the leaf tips with chlorosis and necrosis at the bottom of the wilted area. Zinc Function:

Component of numerous enzymes. Deficiency: Leaves chlorotic and necrotic, with the top

leaves affected first; shedding; whitish chiorosis between the veins of the bottom leaves.

Cobalt Function: A component of the Vitamin B12 complex (coenzyme). Deficiency: Top leaves

chlorotic; roots considerably reduced. Plants require nutrients in order to grow. The

roots absorb the nutrients from the water as dissolved salts. These are the simple

com-pounds found in chemical fertilizers. Organic fertilizers travel a more circuitous

route, first breaking down from complex molecules through microbial action, and then

dissolving into the water. Nitrogen (N), Phosphorous (P) and Potassium (K) are called the

macro-nutrients because plants use large quantities of them The percentages of N, P and K

are always listed in the same order (N-P-K) on fertilizer packages. Calcium (Ca), sulfur

(S), and magnesium (Mg) are also required in fairly large quantities. They are often

called secondary nutrients. Smaller amounts of iron (Fe), zinc (Zn), manganese (Mn), boron

(B), cobalt (Co), copper (Cu), molybdenum (Mo), and chlorine (Cl) are also required These

are called the micro- nutrients. When marijuana germinates, it requires a modest amount of

N and larger amounts of P. This supports vigorous root growth and limits etoliation

(stretching) of the stem When it goes into its vigorous growth stage, usually within two

weeks, marijuana's need for N increases. The nutrient is used in building amino acids, the

sniff protein is made from During the reproductive stage, when the plant flowers, the

female's flower growth is promoted by P and K Plants which are being grown in soil mixes

or mixes with nutrients added such compost, worm castings or manure do better when watered

with a dilute soluble fertilizer, too. When a non-nutritive medium is used, the nutrients

are supplied as a solution in the water from the beginning T"pical formulas used for

the seedling and earlygrowth stages include: 7-9-5, 5-10-5,4-5-3. Formulas for the fast

growth stage usually have a little more nitrogen. Most growers use different formulas for

the different growth stages. Other growers supplement low nitrogen formulas with fish

emulsion or other high nitrogen formulas. Some gardeners use the same ferttlizers

throughout the plant's life cyclc Atypical formula fbr this is 20-20-20. Plants growing

under warm conditions (over 80 degrees) are given less N to prevent stem etoliation.

Plants grown in cool environments are given more N. During flowering a high P formula

promotes flower growth Formulas such as 3-10-4, 5-20-5 and 4-30-12 are used Plants are

sometimes grown using a nutrient solution containing no N for the last 10 days. Many of

the larger leaves yellow and wither as N migrates from old to new growth The fertilizer

should be complete, that is, it should contain all of the secondary and trace elements.

Some fertilizers do not contain Mg This is supplemented using Epsom salts, available at

drug stores. Sometimes growers prefer to use more than one fertilizer. They find that

changing the formulas and ingredients helps to prevent stresses and deficiencies. However,

the chemicals in each fertilizer are blended to remain soluble. Different fertilizer

formulas may react with each other. As a result some of the chemicals may precipitate and

become unavailable to the plants. To prevent this growers use only one fertilizer at each

watering Over fertilization is very dangerous. when plants are under-fertilized more

nutrient can be added, no harm done. Overfertilization can kill a plant quickly. Growers

take no chances when they change hydroponic nutrient-water solutions every 2 weeks. Even

though the solution may have nutrients left, it is probably unbalanced since the plants

have used some of the nutrients, and not others. Temperature, movement, humidity and

content of the air all affect plant growth. Unlike warm-blooded animals, which can

function regardless of the outside temperature, plants rate of metabolism, how fast they

function and grow is controlled by the temperature of the surrounding air. At low

temperatures, under 65 degrees, the photosynthesis rate and growth are slowed The

difference in growth rate is not readily apparent if the temperature dips once in a while

or the low temperatures are not extreme. However, temperatures under 50-55 degrees

virtually stop growth Temperatures in the 40's cause slight temporary tissue damage. when

temperatures dip into the high thirties tissue damage which takes several days to repair

may result, especially in older plants. when temperatures rise above 78 degrees, cannabis'

rate of growth slows once again as the plant uses part of its energy to dissipate heat and

keep its water content constant. The rate of growth continues to slow as the temperature

rises. Photosynthesis and growth stop somewhere in the 90's. When the lights are off,

Photosynthesis stops. Instead, the plants use the sugars and starches for energy and

tissue building The plants do best when the temperature is lower during this part of the

cycle. The fact that the lamps are off; will lower the temperature quite a bit, and

ventilation can be used to cool the space down. Looking at a marijuana leaf under a

magnifying glass, a viewer will notice that there are small "hairs" covering it.

These appendages form a windbreak which slows air movement around the leaf This helps to

modily the temperature by holding air which has been warmed by the tissue surface, similar

to the way hair or fur keeps warm air trapped near the skin. Since plants transpire water,

the air surrounding the leaf surfaces is more humid than the air in the surrounding

environment. Outside, there is usually a breeze so that air is ventilated from the

surface. The breeze removes waste gasses and humidity and brings fresh air containing C02

in contact with the surface. Indoors, air movement is easily achieved using fans. The

movement should be swift but not forceful leaves should have slight movement. Oscillating

fans are convenient means gardeners use to provide an air stream to all sections of the

garden. A dralt which is too strong can be buffered against a wall so that the current

reaches the garden indirectly. Marijuana functions best at a humidity of 40-65%. Higher

humidity causes problems in two ways. First, fungi which attack marijuana become active at

higher humidities. They affect all parts of the plant, but especially the buds, which

contain moisture holding crevices, are dark and have little air movement. The other

problem with high humidity is that plants have a hard time dissipating water transpired by

the stomata (plant pores). The humidity level is a measure of how saturated the air is

with moisture. That is, how much water the air is holding as a percentage of its water

holding potenflal The warmer the air the more moisture it can absorb, so that when the

temperature rises the air becomes less saturated and the humidity goes down, even though

the same amount of water is dissolved in the air. The reverse happens when the temperature

declines. The same amount of water may be in the air, but the air's water holding capacity

is lower so the humidity rises. There are several ways to maintain the proper temperature

and humidity. The easiest method gardeners use to rid a space of excess heat or moisture

is to vent the space. Small spaces such as a closet or shed are easily vented into the

room because of the large surface area in contact with the general space. Room temperature

and humidity conditions are similar to those needed by the plants. Heated rooms may be a

little low in humidity, but the moisture level in the micro environment surrounding the

plants is usually higher. This is caused by evaporation of water from the medium and by

plant transpiration. Since hot air rises and cool air sinks, a fan placed above the plants

pulls out the heated air. Squirrel fans and other ventilation fans make these setups a

snap. Fxperienced gardeners choose fans with the capacity to move the room's cubic area

every 10 minutes. As an example a fan in 200 cubic foot grow space moved 20 cubic feet per

minute. Increasing the rate of air change using a fan has beneficial effects besides

controlling temperature and humidity. A breeeze which causes some movement of the stem

increases its strength When a plant moves in the wind, small tears develop in the tissues.

The plant quickly grows new tissue, thickening and strengthening the stem. A breeze also

increases the amount of C02 available to the plant. C02. Sensible growers know that open

windows are not as good a solution as fans for several reasons. They present a new problem

regarding detection, both by light and odor, and plant pests living outside might use the

passage-way to find new indoor feeding grounds. Some growers use a closed system. The air

is cooled using an air conditioner, the humidity is lowered using a dehumidifier and the

C02 is supplied using a tank Each of these units is connected to a sensor so that they go

on and off automatically. In temperate areas the air conditioner remains on a small part

of the time, except during the summer when it may be called on for heavy dutywork The air

conditioner also dehumidifies the room. A small sized dehumidifier can keep a room at

desired humidity when the temperature is within the acceptable range. Grow spaces located

in basements or attics may get cool during the winter. An electric or gas heater designed

for indoor use is often used to increase the temperature. Electric heaters raise the

temperature, but decrease the humidity of the room because no additional moisture is added

to the air. Gas heaters vented into the grow space provide C02, moisture and heat to the

plants. Plant roots are very sensitive to cold temperatures. Containers placed directly on

a cold floor lose their heat. To conserve warmth the units are set on a pallet or the

floor, or it is covered with a layer of styrofoam sheet, which is both an excellent

insulation material and light reflector. Heat mats and heating cables which are

thermostatically regulated to keep trays and soil in the mid-seventies are sold in many

garden shops. Water in reservoirs is often heated using aquarium equipment. Every plant

needs air to grow. But what are the best atmospheric conditions for a marijuana plant, and

how can they be achieved? This chapter covers the most important factors: optimization of

humidity, carbon dioxide and oxygen levels, temperature, and air circulation. It also

examines the significant effects of carbon dioxide concentration and root aeration, and

explains how these may be controlled to produce the best possible plants. Stomates are

structures through which plants make contact with the atmosphere. Stomates are numerous

small pores in the epidermis of leaves, stems, fruits, and flowers. On leaves, they appear

more on the undersurface than on top. Surrounding each stomate are two elongated cells,

known as guard cells. These specialized cells provide the mechanical means for opening and

closing the stomates. The mechanisms involved in this opening and closure are still widely

at issue, but certainly two contributing factors are C02 concentration and water stress.

(These factors will be discussed in later sections.) The stomates have two important

functions. One is the exchange of gases with the air. Carbon dioxide is drawn into the

leaves for photosynthesis, and the oxygen produced is released into the air, through the

stomates. The other function, which occurs simultaneously, is the release of water vapor

from the leaves. Under normal field conditions this water loss would interfere with

optimal growth. However, with the water culture, this becomes a most beneficial effect.

The movement of water within plants is one of the most important processes in botany. It

is still not clearly known how water flows up and out of the plant, but the

transpiration-cohesion theory offers some explanation. When water evaporates from the

stomates on the leaves (transpiration), a water shortage is created within the leaves. As

a result, water is pulled up through the plant to compensate for the amount lost in

transpiration. (This creates a continuous cycle in which water is absorbed and released

back into the atmosphere.) The pulling effect results from the cohesion, or "sticking

together," of the water molecules. Attraction between the molecules is sufficient to

pull water up the stem from the roots and on into the leaves. Transpiration performs three

major functions. First is the flow of water through the plant; second, the delivery of

minerals; third, the cooling of the leaves and other organs by the evaporation of the

water. Water flow depends on the rate of transpiration. During the reproductive phase of

growth, with relatively high temperatures and low humidity in the growth chamber (see

Chapter 5), adequate water flow is critical. Under normal conditions, such temperatures

and humidity would be extremely harmful, simply because water could not be absorbed from

the soil fast enough, and permanent wilting or thermal death could occur. However, water

culture allows for immediate absorption of water to guarantee that transpiration will

continue at an optimal rate. Transpiration also provides a mechanism for the delivery of

minerals to the rapidly growing shoot tissues. When water moves up through the plant, the

minerals it contains are absorbed by the newly-forming tissues as fast as they can be

delivered. The mineral concentration within the plant then becomes low by comparison with

that of the nutrient solution surrounding the roots; this allows more minerals to move

into the roots along with the water necessary for transpiration. This is why careful

maintenance of the correct concentrations of minerals is so important. The ability of the

plant to transpire is essential for the prevention of thermal death. Transpiration is a

diffusion process, with the water molecules moving from the leaves (an area of high water

vapor concentration) into the air (an area of lower water vapor concentration). Since

water is a good thermal conductor, the heat is dissipated into the air with the water

vapor. Many environmental factors, both extemal and internal, influence the rate of

transpiration. However, the three environmental factors that have the greatest effect on

transpiration are air movement, temperature, and relative humidity. As transpiration

occurs, water molecules gather around the openings of the stomates. When air moves across

the surfaces of the leaves, the water escapes into the air. Not only is air movement

important for removing water vapor; it also brings carbon dioxide into contact with the

stomates. It has been estimated that transpiration proceeds twenty times as fast in moving

air as it does in still air. However, raising the air velocity past a certain point does

not increase the rate of transpiration. (Moreover, as plants become larger, supporting

them in high air velocities becomes very difficult.) Therefore, a gentle breeze is most

effective in removing water vapor. Air circulation through growth chambers has posed a few

engineering problems, but these have been solved. Temperature exerts a drastic influence

on the rate of transpiration. With an increase in temperature, water moves from the leaf

cells to the stomates, where it is then removed into the atmosphere. However, as we have

mentioned, if the temperature rises too high, it may cause thermal injury or death. On the

other hand, if the temperature is too low, adequate transpiration will not occur. Relative

humidity is the water vapor content of the air. It is also the controlling factor in

transpiration. Most greenhouse growers feel that high relative humidities give better

growth results. However, it has been found that high humidity only decreases the amount of

water used during transpiration. Other than that, it has no significant effect on growth.

It is for this reason that humidity is used to control the rate of water flow through the

plant during transpiration. Since our discussion has been focused on the growing of

marijuana, we will investigate the fact that by modifying relative humidity and other

environmental factors, it is possible to control the rate of transpiration and therefore

the growth rate, and influence the production of THC in the plant. The ability of plants

to produce carbohydrates from inorganic materials is the most significant difference

between plants and animals. Carbohydrates can be divided into three basic food groups, all

of which contain carbon, hydrogen, and oxygen. Production of carbohydrates in plants takes

place in order to supply energy (sugars), build cell walls (cellulose), and provide food

storage (starch). Some carbohydrates (the sugars) are water-soluble, while others (starch

and cellulose) are not. The most common carbohydrates are sucrose (C12H22011), glucose

(C6H1206), and starch, which consists of chains of glucose units. Incorrect carbon dioxide

concentration is frequently the factor that keeps photosynthesis from proceeding at its

maximum rate, and therefore limits the production of carbohydrates as well. This is

because the concentration of C02 in the atmosphere is .03 percent or 300 ppm (parts per

million), which is far below the optimal amount that plants can use. However, an increase

in the carbon dioxide concentration to levels above 3,000 ppm produces inhibitory effects.

This is largely due to the increased production of carbonic acid, which results in a

reduction in pH. The reduction of pH causes closure

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