Two questions for a veteran

Humidity Humidity is relative, that is, air holds different quantities of water at different temperatures. Relative humidity is the ratio between the amount of moisture in the air and the greatest amount of moisture the air could hold at the same temperature. In other words, the hotter it is, the more moisture air can hold; the cooler it is, the less moisture air can hold. When the temperature in a grow room drops, the humidity climbs and moisture condenses. For example, an 800 cubic foot (10 x 10 x 8 feet) grow room will hold about 14 ounces of water when the temperature is 70 degrees F and relative humidity is at 100 percent. When the temperature is increased to 100 degrees F, the same room will hold 56 ounces of moisture at 100 percent relative humidity. That's four-times as much moisture! Where does this water go when the temperature drops? It condenses, just like dew condenses outdoors, onto the surface of plants and grow room walls.

A 10 x 10 x 8 foot (800 cubic feet) grow room can hold:

4 oz. of water at 32 degrees F.
7 oz. of water at 50 degrees F.
14 oz. of water at 70 degrees F.
18 oz. of water at 80 degrees F.
28 oz. of water at 90 degrees F.
56 oz. of water at 100 degrees F.

Relative humidity increases when the temperature drops at night. The more temperature variation, the greater the relative humidity variation. Supplemental heat or extra ventilation is often necessary at night if temperatures fluctuate more than 15 degrees F.

Cannabis Clue – The moisture holding capacity of air doubles with every 20o F increase in temperature


Cannabis grows best when the relative humidity range is from 40 to 60 percent. As with temperature, consistent humidity promotes healthy, even growth. Relative humidity level affects the transpiration rate of the stomata. When humidity is high, water evaporates slowly. The stomata close, transpiration slows and so does plant growth. Water evaporates quickly into dryer air causing stomata to open, increasing transpiration, fluid flow and growth.
Warning! Air that holds 16 ounces of water at 75 degrees F will hold only 10 ounces at 60 degrees, causing 6 ounces of water to condense out of the air into the room.
Transpiration in arid conditions will be rapid only if there is enough water available for roots to draw in. If water is inadequate, stomata will close to protect the plant from dehydration, causing growth to slow.
Measuring Relative Humidity
Relative humidity control is an integral part of insect and fungus prevention and control. Humidity above 80 percent discourages spider mites but promotes fungus, root and stem rot. Humidity levels below 50 percent reduce the chances of fungus and rot.

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AlteredBeast said:

I need to know the following. First, explain to me how the level of humidity effects plant growth. What happens if the humidity is too low, too high, optimal, and in which stages of growth is humidity level most important?

Next, I need to know about light leaking onto the flowering plants. What will happen and how much light will it take to make an effect?

I've read alot of threads on riu so far so I know that there are alot of you guys and gals out there who are full of useful info on these two subjects so dont be shy, I wanna know everything you know.

And just for fun, have any of you ever tried The Third Dimension by TGA? If so how was it? Quality smoke? Worth growing?

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earlymorninstonepeomp said:

"First, explain to me how the level of humidity effects plant growth. What happens if the humidity is too low, too high, optimal, and in which stages of growth is humidity level most important"?
Environmental conditions influence cannabinoid biosynthesis by modifying enzymatic systems and the resultant potency of Cannabis. High altitude environments are often more arid and exposed to more intense sunlight than lower environments. Recent studies by Mobarak et al. (197 of Cannabis grown in Afghanistan at 1,300 meters (4,350 feet) elevation show that significantly more propyl cannabinoids are formed than the respective pentyl homologs. Other strains from this area of Asia have also exhibited the presence of propyl cannabinoids, but it cannot be discounted that altitude might influence which path of cannabinoid biosynthesis is favored. Aridity favors resin production and total cannabinoid production; however, it is unknown whether arid conditions promote THC production specifically. It is suspected that increased ultraviolet radiation might affect cannabinoid production directly. Ultraviolet light participates in the biosynthesis of THC acids from CBD acids, the conversion of CBC acids to CCY acids, and the conversion of CBD acids to CBS acids. However, it is unknown whether increased ultraviolet light might shift cannabinoid synthesis from pentyl to propyl pathways or influence the production of THC acid or CBC acid instead of CBD acid.
Take what you will from that.......s far as "light leaking".....well i guess at least a few times an outdoor plant will be on he receiving end of a full moon during its life cycle sooooo......no more than what one would expect during a full moon at worst and.....none at all if you're smarter than the light
TGA...Noooope. Lemon G yes

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