PALE. The inner, and usually smaller of two scaly bracts immediately subtending the grass flower in a spikelet. With the lemma it forms the outer hull of the grass seed.

PANICLE. A many branched flower head with flowers at the end of each branch. Annual Bluegrass is typical of a panicle type inflorescence.

PATHOGEN. Any disease-producing organism, parasite, or virus.

PERCHED WATER TABLE. A soil layer above the normal water table that remains nearly soaked after watering due to an underlying layer of coarse aggregates, usually drainage rock.

PERCOLATION. The downward movement of water out of the root zone.

PERENNIAL. A plant that lives for more than two years.

PRICKLE. A layer of cells below the endodermis, the tissue from which branch roots originate.

PESTICIDE. Any chemical or physical agent that destroys pests. For example: NEMATICIDE, herbicide, insecticide, fungicide, acaricide, rodenticide.

PETIOLE. A leaf stalk, grasses do not have petioles.

PH. The negative logarithm of the hydrogen ion concentration in solution. Used as relative measure of acidity and alkalinity.

PHLOEM. Living conduction tissue whose main function is transporting food.

PHOTOPERIOD. The period during the 24 hours when it shines at physiological intensities.

PHOTOSYNTHESIS. The use of light energy to synthesize organic molecules within the plant.

PHYTOMER. An internode with a leaf, plus the portion of the node at the upper end and a bud, plus a portion of the node at the lower end.

PHYTOTOXIC. Injurious or poisonous to plants. Incorrect use of pesticides often results in phytotoxicity problems.

PISTIL. A female flower part, collectively made up of the stigma, style, and ovary.

PLUGGING. Vegetative propagation of grasses by means of small sod pieces. Zoysia is a commonly plugged species.

POISON. Signal word indicating a highly toxic pesticide. The oral LD50 range is 0-50 mg/kg. See DANGER.

POLYSTAND. A turfgrass community composed of two or more species or cultivars.

POLYSTAND COMPATIBILITY. Refers to whether or not turfgrasses will grow together to make a desirable turf.

PORE SPACE. The space between soil particles.

POSTEMERGENCE. After germination and emergence from the soil. Commonly used in reference to herbicide classification.

PPM. Parts per million.

PREEMERGENCE. Prior to germination and emergence from the soil. Used to classify herbicides.

PREPLANT. A herbicide or other pesticide applied anytime before the crop is planted.

PROCUMBENT. Growing along the ground, not erect.

PROPAGULE. In turf, vegetative segments capable of initiating new plants.

PROTECTANT. A chemical applied to the plant in advance of the arrival of the pathogen. Many fungicides are classified as protectants.

PROSTRATE. Growing flat along the ground.

PUBESCENT. Having soft hair or down.

PUPA. The resting stage of an insect which passes through four stages of develop-ment: egg, larva, pupa, and adult in its maturation.

PURITY. The percentage by weight of pure seed in a package of seed.

PUSTULE. A small, raised blister, or pimplelike swelling that may rupture the epidermis to expose the causal agent.

PWP. Permanent Wilting Point. The soil moisture level at which a plant wilts and will not recover.

PYCNIDIUM. A closed, flasklike, fruiting structure found in some fungi. It commonly bears pycnidiospores which may be called conidia.