{"id":8002,"date":"2023-04-21T17:16:58","date_gmt":"2023-04-21T15:16:58","guid":{"rendered":"https:\/\/marijuanagrowing.com\/?p=8002"},"modified":"2024-01-31T13:36:11","modified_gmt":"2024-01-31T12:36:11","slug":"air-chapter-16","status":"publish","type":"post","link":"https:\/\/marijuanagrowing.com\/air-chapter-16\/","title":{"rendered":"Air – Chapter 16"},"content":{"rendered":"\n
Fresh air is essential to grow healthy gardens. Greenhouse and indoor gardens depend on a supply of fresh air. This precious resource often defines crop success or failure. Outdoor air is abundant and packed with the carbon dioxide (CO2) necessary for plant life. For example, the level of CO2 in the air is about 0.039 percent (389 ppm), but in a field of rapidly growing canna\u00adbis it could be only 250 ppm\u2014approximately a third of normal on a very still day. Wind blows in fresh CO2-rich air. Rain washes air and plants of dust and pollutants. The outdoor environment is often harsh and unpredictable, but there is always fresh air. CO2- rich air is even more critical in indoor and greenhouse gardens. It must be carefully controlled to replicate the best of the outdoor atmosphere.<\/p>\n\n\n\n
Air in a garden room or greenhouse must be moved either by natural currents or mechanically to simulate outdoor environments. Stale, depleted air is ventilated out and new CO2- rich air is drawn or forced into garden rooms and greenhouses. Air must be circulated to prevent stagnant air and stratification around leaves and within the structure.<\/p>\n\n\n\n
Carbon dioxide and oxygen provide basic building blocks for plant life. Oxygen (O2) is used for respiration\u2014burning carbohydrates and other foods to provide energy. CO2 must be present during photosynthesis. Without it, a plant will die. CO2 combines light energy with water to produce sugars. These sugars fuel the growth and metabolism of cannabis plants. With reduced levels of CO2, growth slows to a crawl. Except during darkness, a plant releases more O2 than is used and uses much more CO2 than it releases.<\/p>\n\n\n\n
Bottom branches are pruned to allow for extra airflow under plants. Fresh air is essential to keep plenty of carbon dioxide available for plants.<\/em><\/p>\n\n\n\n Extra airspace in this greenhouse will run out before harvest. The buds will soon touch the roof. The ventilation fans run full speed 24 hours a day.<\/em><\/p>\n\n\n\n Roots use air, too. Oxygen must be present along with water and nutrients for the roots to be able to absorb nutrients. Compacted, water-saturated soil has little space for the air that roots need, and nutrient uptake stalls.<\/p>\n\n\n\n Animals regulate the amount of air inhaled and the carbon dioxide and other elements exhaled through the nostrils via the lungs. In cannabis, O2 and CO2 flows are regulated by stomata. The larger the plant, the more stomata it has to take in CO2 and release O2. The greater the volume of plants, the more fresh, CO2-rich air they will need to grow quickly. When stomata are clogged with dirt and filmy spray residues, they do not work properly, thus restricting airflow. Keep foliage clean. To avoid clogging stomata, spray foliage with tepid water a day or two after spraying with any pesticides, fungicides, or nutrient solutions.<\/p>\n\n\n\n Stomata function is rather complex and is controlled by many variables, including external triggers such as light; increased or decreased internal pressure based on supply and evaporative potential; and the presence or concentration of certain gases such as CO2<\/strong>. For example, a 40-inch (1 m) tall plant can easily transpire a gallon (3.8 L) per day when the humidity is below 50 percent. How- ever, the same plant will transpire about a half-pint (0.2 L) on a cool, humid day.<\/p>\n\n\n Stomata are microscopic pores on leaf under- sides that are similar to an animal\u2019s nostrils.<\/em><\/p>\n\n\n\n Molecules\u2014O2, CO2, H2O, etc.\u2014are moved to the leaf surface in a mass flow situation known as the atmosphere. When the air is still, molecules migrate around under the energy of their own vibration\u2014a slow process. When the atmosphere moves, molecules move more quickly. When they reach the stomata, molecules encounter their first barrier to movement, the one at the opening, and like a port on the sea with lots of ships, this slows the movement because the molecules diffuse under their own power into the stomata and out of the stomata; the opening is a two-way street. Circulation in the area moves away those molecules that have exited faster and brings new ones to the stomata faster. Once inside, they vibrate their way across the cavity to the next barrier, located at the cell membrane, and the crowding begins again. Ventilation brings new molecules in while flushing old ones out. Ventilation can also be used to distribute heat and to control humidity.<\/p>\n\n\n\n Temperature is a dominant factor for plant growth as well as most life processes on earth. An accurate thermometer is essential to measure temperature in all <\/em>garden rooms. Mercury or liquid thermometers are typically more accurate than spring or dial types, but they are ecologically unsound. An inexpensive thermometer will collect basic information, but the ideal thermometer is a day\/ night or maximum\/minimum type that measures how low the temperature drops at night and how high it reaches during the day. See chapter 15, Meters<\/em>, for more information on thermometers.<\/p>\n\n\n\n Under normal conditions, the ideal temperature range for cannabis growth is 72\u00baF to 76\u00baF (22.2\u00baC\u201324.4\u00baC). At night, the temperature can drop 5 to 10 degrees with little noticeable effect on growth rate. The temperature should not drop more than fifteen degrees or excessive humidity and mold might become problems. Daytime temperatures above 85\u00baF (29.4\u00baC) or below 55\u00baF (12.8\u00baC) will slow or stop growth. Maintaining the proper, constant temperature in garden rooms and greenhouses promotes strong, even, healthy growth. Make sure plants are not too close to heat sources such as ballasts, heaters, and heating vents, or they may dry out, maybe even get heat scorch. Cold intake air will also stunt plant growth.<\/p>\n\n\n\n Cannabis regulates its oxygen uptake in relation to the ambient air temperature rather than the amount of available O2. Plants use a lot of O2; in fact, a plant cell uses as much O2 as a human cell. The air must contain at least 20 percent O2 for plants to thrive.* Leaves are not able to release O2 at night, but roots still need it to grow. A plant\u2019s respiration rate approximately doubles every twenty degrees. Oxygen use by roots increases as they warm up, which is why fresh air is important both day and night. Temperatures above 85\u00baF (29.4\u00baC) are not recommended even when using CO2 enrichment. When it\u2019s too warm, photorespiration occurs faster than the plant can compensate, the system short-circuits, and O2 takes the place of CO2; this in turn shuts down the Calvin cycle** and thus the conversion of light to carbohydrates and energy.<\/p>\n\n\n\n Stomatal function: <\/strong>Increased internal pressure from active roots, increased temperature, or a blockage in the exit pathway, along with suitable triggers such as a decrease in internal CO2 levels and appropriate light triggers (usually UV light), allow for the guard cells of the stomata to become turgid and thus open (through other sometimes- complex processes involving potassium shifts and so on).<\/p>\n\n\n\n Decreased internal pressure from low temperatures, decreased water availability in the root zone, high internal levels of CO2, lack of environmental triggers, or a faster demand at the exit pathway than can be supplied, cause a wilting or slacking in the guard cells, which partially or totally closes them. This limits the amount of water escaping the plant and provides some protection. Either case can cause an imbalance between water need and fulfillment.<\/p>\n\n\n\n Humidity is similar to the pipe in a water line. The temperature is the power to run the pump, which is the vascular system of the plant. The valve after the pump and before the end is the stoma. The other side of the valve is the container or sink\u2014demand. As the power is increased to the pump, it pumps faster and more will flow. The larger the pipe, the more that will flow. The more open the valve the more that will flow. The larger the container at the end of the lines, the bigger the results of the system, because it can deliver more. Even though the pump may be pumping as fast as possible, the pipes have to be big enough to deliver the load. The valve has to be open enough to deliver, and the container has to be big enough to handle the load. If the pump is barely moving but the pipes are huge, then there is no pressure and the water will stop flowing or reaching all the containers (the valve is closed more and more to hold pressure in the system to keep water available for the life reactions in respiration, etc.).<\/p>\n\n\n\n This photo of half-opened stomata, the mouthlike openings on leaf undersides, was magnified 2500 times.<\/em><\/p>\n\n\n\n The opposite is true when the pump runs rapidly and the pipes are really small: not enough load is delivered and the process stops. If the pump runs wide open and the pipes are really big, then pressure drops to zero again and function stops; the same is true the other way. The over- all system will deliver zero load at the extremes of these four situations. So, in a situation where water (load) was available, where the temperature (power) was normal, where the container (sink) was appropriate, and the pipes very small, the valve would be more and more open to get the load delivered.<\/p>\n\n\n\n *By volume, dry air contains about 78.09 percent nitrogen, 20.95 percent oxygen, 0.93 percent argon, 0.039 percent carbon dioxide (390 ppm), and trace amounts of other gases. Note the ambient level of CO2 has increased from 350 ppm 50 years ago; as CO2 rises, the earth gets warmer.<\/p>\n\n\n\n **The Calvin cycle <\/strong>[aka Calvin\u2013 Benson-Bassham (CBB) cycle, reductive pentose phosphate cycle, or C3 cycle] is a series of biochemical redox reactions that take place in the stroma of chloroplasts in photosynthetic organisms. The light-independent reactions of photosynthesis are chemical reactions that convert carbon dioxide and other compounds into glucose. Melvin Calvin, James Bassham, and Andrew Benson discovered the cycle at UC Berkeley by using the radioactive isotope carbon-14.<\/p>\n\n\n\n Photorespiration<\/strong>, is a process in plant metabolism by which RuBP (a sugar) has oxygen added to it by RuBisCO (an enzyme) instead of carbon dioxide during normal photosynthesis. This is the beginning step of the Calvin- Benson-Bassham cycle. This process reduces efficiency of photosynthesis in C3 plants.<\/p>\n\n\n\n Under proper conditions when the water supply is abundant, higher air temperatures step up metabolic activity and speed up growth. The warmer the air is, the more water it is able to hold. This moist air often restrains plant functions and decelerates growth rather than speeding it. Typically, as air temperature rises, humidity falls and plants use water faster; then later in the light cycle, because more water moves into the air, the air becomes more humid. When the lights go out or air temperature naturally cools, humidity levels begin to rise until saturation, at which point moisture condenses out of the air. Moving the air slows or eliminates this process. Night- time\u2014when the lights go out\u2014often causes complications; problems result from excess humidity and moisture condensation when the temperature drops.<\/p>\n\n\n\n A plastic greenhouse helps regulate temperatures outdoors. Indoors, temperature regulation is accomplished in a variety of ways: air ventilation, air circulation, air conditioning, and more.<\/em><\/p>\n\n\n\n Heat buildup during warm weather can catch any gardener off guard and cause serious problems. Ideal garden rooms are located underground, in a basement, taking advantage of the insulating qualities of Mother Earth. With the added heat of the HID and hot, humid weather outdoors, an indoor room can heat up rapidly and greenhouse tempera\u00adtures can soar. More than a few garden\u00aders in the USA have lost their crops to heat stroke during the Fourth of July weekend, which is the first big holiday of the summer, and everybody wants to get away to enjoy it. Some gardeners for\u00adget or are too paranoid to maintain good ventilation in the garden room while on vacation. Temperatures can easily climb to 100\u00baF (37.8\u00baC) or more in garden rooms and greenhouses that are poorly insulated and vented. The hotter the air temperature, the more ventilation and water that are necessary.<\/p>\n\n\n\n Winter weather comes early to some gardens. This gardener was able to harvest his crop a long time before the snow arrived.<\/em><\/p>\n\n\n\n The cold of winter is the other tempera\u00adture extreme. Think back and remember past winter storms in your climate. Elec\u00adtricity often goes out in cities and sur\u00adrounding areas. Water pipes freeze and heating systems fail. Some residents are driven from their homes until electric\u00adity can be restored, often days later. In such cases gardeners return to find their beautiful gardens wilted, stricken with the deepest, most disgusting green only a freeze can bring. Broken water pipes, ice everywhere! It is difficult to combat such acts of God, but if possible, always keep garden rooms and greenhouses above 50\u00baF (10\u00baC) and definitely above freezing, 32\u00baF (0\u00baC). If the temperature dips below this mark, the freeze will rupture plant cells, and foliage will die back or, at best, grow slowly. Growth slows or stops when the temperature dips below 55\u00baF (12.8\u00baC). Stressing plants with cold weather conditions is not recommended; it may yield a proportionately higher THC content, but it will reduce plants\u2019 overall productivity.<\/p>\n\n\n\n A thermostat <\/strong>measures temperature and controls it by turning on or off a device that regulates heating or cool\u00ading, keeping the temperature within a predetermined range. A thermostat can be attached to an electric or combus\u00adtion heater. Often indoor garden rooms can take advantage of individually thermostat-controlled electric baseboard heaters in each room.<\/p>\n\n\n\n A thermostat can be used to control cooling vent fans in all but the coldest garden rooms and greenhouses. When it gets too hot in a room, the thermostat turns on the vent fan, which evacuates hot, stale air. The vent fan remains on until the desired temperature is reached, then the thermostat turns off the fan. A thermostat-controlled vent fan offers adequate temperature and humidity control for many garden rooms and green\u00adhouses. A refrigerated air conditioner can be installed if heat and humidity are a major problem, but such devices draw a lot of electricity. If excessive heat is a problem but humidity is not a concern, use a swamp cooler. These evaporative coolers are inexpensive to operate and keep garden rooms and greenhouses cool in arid climates.<\/p>\n\n\n\n An accurate thermometer is necessary equip\u00adment for all indoor, greenhouse, and outdoor cannabis gardens.<\/em><\/p>\n\n\n\n Ambient temperature regulation is essential for healthy cannabis growth regardless of whether plants are grown indoors, outdoors, or in a greenhouse.<\/em><\/p>\n\n\n\n A combination thermometer\/hygrometer that registers maximum and minimum readings helps keep the garden room\u2019s atmosphere constant.<\/em><\/p>\n\n\n\n Common thermostats include <\/strong>single-stage and two-stage. The single-stage thermostat controls a device that keeps temperature the same both day and night. A two-stage thermostat is more expensive but can be set to main\u00adtain different daytime and nighttime temperatures. This convenience can save money on heating and provides exacting control over plant growth.<\/p>\n\n\n\n Note: <\/strong>Sometimes a slight day\/night differential in temperature, even as slight as two degrees, can bring about physiological changes in plant growth, such as intense foliage coloration or an increased production of resin and other metabolites.<\/p>\n\n\n\n This garden room is equipped with a thermo\u00adstat that controls both day and night tempera\u00adtures. On the left is a CO2 controller.<\/em><\/p>\n\n\n\n This thermostat is controlled with a mercury switch visible in the center-left of the photo.<\/em><\/p>\n\n\n\n Insulated garden-room walls help immensely to keep garden-room temperature independent of outside atmospheric conditions.<\/em><\/p>\n\n\n\n A directional air conditioner directs cool air over the entire area of this garden room.<\/em><\/p>\n\n\n\n Many electronic garden room and greenhouse controllers <\/strong>have been developed in the last decade. These controllers can operate and integrate every appliance in garden rooms and greenhouses. More sophisticated con\u00adtrollers integrate the operation of CO<\/strong>2 <\/strong>equipment and vent and intake fans. If temperature and humidity regulation are causing cultural problems in your garden rooms and greenhouses, consider purchasing a controller.<\/p>\n\n\n\n Uninsulated <\/strong>garden rooms and green\u00adhouses experience significant tempera\u00adture fluctuations and require special consideration and care. Before growing in such a location, make sure it is the only choice. If forced to use a sunbaked attic that cools at night, make sure maximum insulation is in place to help balance temperature instability. Enclose the garden room or greenhouse to con\u00adtrol heating and cooling.<\/p>\n\n\n\n When CO<\/strong>2 <\/strong>is enriched <\/strong>to levels of 0.7 to 0.9 percent (700\u2013900 ppm), a temperature of 75\u00baF to 80\u00baF (23.9\u00baC\u2013 26.7\u00baC) promotes faster exchange of gases. Photosynthesis and chlorophyll synthesis are able to take place at a faster rate, causing plants to grow more rapidly. Remember, this higher tempera\u00adture increases water, nutrient, and space consumption, so be prepared. Unless in a functioning sealed room, CO2- enriched plants still need ventilation to remove stale, humid air and promote plant health.<\/p>\n\n\n\n The temperature in the garden room tends to stay the same, top to bottom, when the air is circulated with an oscil\u00adlating fan or fans. In an enclosed garden room, HID lamps and ballasts keep the area warm. Placing remote ballasts near the floor on a shelf or a stand also helps break up air stratification by radiating heat upward, while protecting them from water splashes and floods. Garden rooms in cool climates stay warm during the day when the outdoor temperature peaks, but they often cool off too much at night, when cold temperatures set in. To compensate, gardeners turn on the lamp at night to help heat the room, but leave it off during the day. Sometimes it is too cold for the lamp and ballast to maintain satisfactory room temperatures.<\/p>\n\n\n\n A barrel filled with water <\/strong>(or a nutrient reservoir) will collect heat during the day. At night, when temperatures cool, the heat banked in the water slowly radiates to warm the growing area. This passive means of heating requires only a container and space to locate it. See chapter 11, Greenhouses<\/em><\/a>, for more information.<\/p>\n\n\n\n Garden rooms in homes are usually equipped with a central heating and\/ or air conditioning <\/strong>vent. The vent is usually controlled by a central thermo\u00adstat that regulates the temperature of the home. By adjusting the thermostat to 72\u00baF (22.2\u00baC) and opening the door to the garden room, it can stay a cozy 72\u00baF (22.2\u00baC). However, using electric power is expensive and often wasteful. Keeping the thermostat between 60\u00baF and 65\u00baF (15.6\u00baC\u201318.3\u00baC), coupled with the heat from the HID system, should be enough to sustain 75\u00baF (23.9\u00baC) temperatures. Other supplemental heat sources such as inefficient incandescent lightbulbs and electric heaters are expensive and draw extra electricity, but they provide instant heat that is easy to regulate. Propane and natural gas heaters increase temperatures and burn oxygen from the air, creating CO2 and water vapor as by-products. This dual advantage makes using a CO2 generator economical and practical, especially in greenhouses. Make sure to properly vent all enclosed spaces when generating CO2 with fossil fuels.<\/p>\n\n\n\n Air conditioning is expensive but often already installed in many homes.<\/em><\/p>\n\n\n\n This propane heater is also a CO2 generator.<\/em><\/p>\n\n\n\n Electric oil-filled radiators are a good option for many small gardens. They can supply just enough heat during nighttime hours to main\u00adtain temperature levels and not let humidity get out of control.<\/em><\/p>\n\n\n\n Kerosene heaters with an open flame <\/strong>generate heat and CO2. Look for a heat\u00ader that burns its fuel efficiently and com\u00adpletely with no telltale odor of the fuel in the room. Do not use old kerosene heaters or fuel-oil heaters if they burn fuel inefficiently. A blue flame is burning all the fuel cleanly. A red flame indicates only part of the fuel is being burned. I\u2019m not a big fan of kerosene heaters and do not recommend using them. The room must be vented regularly to avoid build\u00adup of toxic carbon monoxide (CO), also a by-product of combustion.<\/p>\n\n\n\n Diesel oil <\/strong>is a common source of indoor heat. Many furnaces use this dirty, pol\u00adluting fuel. Woodstoves pollute too, but work well as a heat source. A vent fan is extremely important to exhaust polluted air and draw fresh air into a room heated by an oil furnace or a woodstove.<\/p>\n\n\n\n Propane and LP gas heaters <\/strong>are the most common way to heat greenhouses. Some of these heaters have an open flame, others do not. Combustion burns oxygen out of the air, which in turn increases CO2 levels in the greenhouse.<\/p>\n\n\n\nStomata<\/h3>\n\n\n\n
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