Grower's Dictionary A-lamp n. standard incandescent lamp. absorption n. The process by which plants take up water through their roots. AC/H abbr. Air Changes per Hour. Measure of ventilation in enclosed spaces derived from ventilation fan CFM and cubic volume of a given space. 10 AC/H would indicate ventilation adequate to completely replenish air in a given space ten times per hour. 20 AC/H is considered optimal for cannabis cultivation, cooling load notwithstanding. acid an acidic solution. A solution with a pH of 0-7.0. acidify v. to lower the soil's pH to meet the characteristics of acid soil. activated carbon n. ionized carbon granules, typically the main component in filters, effective in removing impurities from air and water. Activated carbon filters are effective in odors from air. activator n. any of various substances such as microorganisms and nutrients, which, when added to a compost pile, speed the breakdown of organic matter. Also called compost activator and compost inoculant. active air intake n. means of ventilating enclosed spaces with the use of mechanical fans or pumps. (ant. passive air intake). adsortion n. condensation on the soil's surface. aerate v. 1. to expose to the air. 2. to charge with air. Hydroponics operations often aerate nutrient solutions to reduce algae and bacterial growth and increase oxygenation. aeration n. an exchange of air in the soil with air from the atmosphere. Earthworms accomplish this, as does digging and turning the soil to loosen it. aeroponic n. variant of hydroponic cultivation in which liquid nutrient chemicals are aerosolized and sprayed on plant roots to increase oxygenation and nutrient solubility. Aeroponics is considered an advanced form of hydroponics and can help achieve slightly greater yields and faster growth when properly tended. algae n. simple organisms of the plant kingdom, lacking roots, stems, leaves, and flowers. Most grow in water, such as seaweeds or pondweeds. Seaweeds are valuable as fertilizers. alternate adj. 1. Placed at uneven sequences upon the stem, as alternate leaves, which are solitary at the junction with the stem, in distinction from opposite or whorled. 2. Opposite to the intervals between organs, as petals that are alternate with sepals, or stamens with petals. Cannabis plants are often transferred from vegetative growth to flowering when upper leaf stems begin to alternate. aluminum sulfate n. a colorless salt used as a soil amendment to increase soil acidity. amendment n. a term for any conditioner or material (like lime, gypsum, etc.) that is added or worked into the soil to make it more productive. Soil amendment is often required for successful outdoor growing. ammonium nitrate n. 1. An inorganic fertilizer used to add nitrogen to the soil. 2. The form that nitrogen takes in numerous commerical fertilizers. ammonium sulfate n. an inorganic fertilizer applied to soil (20.6% N) ampere (AMP) n. measure of electric current strength in the meter-kilogram-second system. It is the steady current that when flowing in straight parallel wires of infinite length and negligible cross section, separated by a distance of one meter in free space, produces a force between the wires of 2 × 10-7 newtons per meter of length. annual n. plant that lives one season or up to one year. Annuals can be carried over into a successive seasons by preventing them from setting seed. Cannabis is an annual plant. anther n. the part of a stamen that contains the pollen, usually located at the end of a slender stalk often in the center of a blossom. ampere (AMP) n. measure of electric current strength in the meter-kilogram-second system. It is the steady current that when flowing in straight parallel wires of infinite length and negligible cross section, separated by a distance of one meter in free space, produces a force between the wires of 2 × 10-7 newtons per meter of length. apatite n. 1. Chief mineral found in phosphate rock. 2. An inorganic compound found in bones; a component of bone meal. aphid n. any of several kinds of small, many- colored sucking insects, usually congregate on new growth (which often becomes distorted) of a great variety of plants, including ornamentals, like roses, and vegetables, like cabbage and broccoli. Easily controlled by insect predators, insecticidal soap, botanical insecticides, or traditional pesticides. aphid trap n. a pheromone-baited (scent-baited) device to lure and capture aphids. Aphytis wasp n. (see scale parasite.) apophyllous adj. in botany, having distinct leaves, applied to a whorled flower with distinct sepals and petals arc n. luminous discharge of electricity between two electrodes in HID lighting. arc discharge n. transfer of electricity across two electrodes (anode and cathode), characterized by high electrode current densities and a low voltage drop at the electrode. (see high intensity discharge). arc tube n. enclosure which contains the luminous gases and also houses the arc. attenuate adj. tapering gradually to a narrow point. Most cannabis strains are known for their natural attenuate phenotype, similar to a "pine tree." Training, pruning, and other methods are used to alter the shape to avoid detection, as well as enhance branching. asexual propagation v. (see clone) auxin n. 1. naturally occurring plant hormone which promotes branching and root growth 2. organic substance characterized by its ability to promote growth, particularly of roots. It is an active ingredient in rooting compounds. axis n. the stem; the central part or upright support of a plant to which organs or parts are attached.