Wine Grape Growing
PEDICEL. A stalk of one flower or fruit in a cluster.
PEDUNCLE. The portion of the rachis from the shoot stem to the first branch of the cluster.
PERENNIAL WEEDS. Weeds with a life cycle greater than two years. Perennial weeds reproduce by seed and vegetative organs, such as rhizomes or tubers.
PERENNIAL WOOD. It is the permanent wood of a grapevine. It is the older, "woodier", thicker wood of the trunk & cordons of the vine.
PERMANENT WILTING POINT. The soil moisture content at which plants will not recover from wilting.
pH. A numerical measure of the acidity or hydrogen ion activity of a substance, e.g., grape juice or soil.
PHENOLS. A varied group of compounds found mainly in skins, stems and seeds in the case of grapes. They include anthocyanin, tannins and many flavor compounds. Precipitated, they form an important part of wine's sediment and play a considerable role in wine ageing.
PHERMONE. A chemical substance (i.e., sex attractant) produced by an animal that serves as a stimulus to other individuals of the same species for a behavioral response.
PHOTOSYNTHESIS. The formation of carbohydrates (sugars, mainly glucose and fructose) in the vine (mostly stored in the fruit) from water and carbon dioxide, by the action of sunlight on the chlorophyll in the vine (produced mostly in the leaves).
PHYLLOXERA. Grape phylloxera (Daktulosphaira vitifoliae) is an aphid-like insect that feeds on grape roots, native to the eastern U.S. where American grape species developed a natural tolerance. Susceptible plants decline and die.
PHYTOTOXIC. Causing injury or death of plants or portions of plants.
PIERCE'S DISEASE. A bacterial infection of the vine that is spread by an insect called the blue-green sharpshooter.
PLANT PENETRANT. An adjuvant that enhances a liquid's ability to penetrate plant roots, leaves, and stems.
PPM. Parts per million, a unit of concentration often used when measuring levels of materials in air, water, etc. One ppm is one part in 1,000,000. The common unit mg/liter is equal to one ppm.
POWDERY MILDEW. A fungal disease of the vine.
PRIMORDIA. Primordia are the growing points of a bud.
PRIMORDIAL SHOOTS. The buds which develop on this year's fruiting wood. They will give rise to the fruiting shoots for next year.
PRUNING. Pruning is the removal of portions of the vine for the purpose of maintaining its size and productivity. The size and productivity is maintained by ensuring that the vine retains a proper number of fruiting buds.
PRUNING WEIGHT. Pruning weight is determined by the amount of wood that is pruned off one vine in a single season. This can be used in formulas to determine how many buds should be removed and/or left on the vine as part of balanced pruning techniques.
PTO. Power take off shaft. The part of a tractor used to transmit power to a wide variety of implements.