Keys Dictionary

Word	Meaning
Perennial	Living for several or many years.
Perianth	The collective term for calyx and corolla of a flower. The term is derived from Greek words translated as peri, 'around' and anthos, 'flower'.
Perigynous	Referring to flowers in which the sepals, petals and stamens are fused at the base to form a cup-shaped structure called a hypanthium or floral tube.
Persistent	The retention of plant structures after their normal purpose has been fulfilled. Caducous refers to falling early, and deciduous to falling seasonally.
Perulae	The scales of a leaf bud..
Perulate	Refers to one of the scales of a leaf bud.
Petal	A single unit of the corolla of a flower.
Petiolate	With a leaf stalk, not sessile.
Petiole	The stalk of a leaf. In compound leaves, the petiole changes into the rachis at the first leaflet pair.
Petiolule	The stalk of an individual leaflet in a compound leaf. Petiolulate means having a petiolule.
Pheromone	Pheromones are specifically designed chemicals, released into the environment, that trigger behavioural responses in members of the same species, or responses in other specific organisms, such as insects. Fig trees attract their pollinator wasps by releasing species-specific volatile compounds that act as pheromones when the flowers are ready to be pollinated. Each species of fig-pollinator wasps, for example, is matched to a specific species of fig tree, and the female wasp can only detect pheromone-like scents emitted by its partner species of fig tree.
Phloem	Phloem is living tissue that moves sap containing sucrose and other organic nutrients throughout the plant as needed. The movement in phloem is multi-directional from areas storing sugars to areas using sugars. In trees, the phloem is the innermost layer of the bark. Beneath the phloem lies a layer of xylem.
Photoperiodism	The plant's physiological response to changes in day and night length. This enables plants to adapt to seasonal change.
Photosynthesis	A process by which plants, and some other life forms, use energy from sunlight to synthesise, or build, carbohydrates from water and carbon dioxide. Carbohydrates in various chemical forms fuel the plant's activities. In this complex process, oxygen is released, which maintains atmospheric oxygen levels that are critical for life on earth.
Phototropism	Bending of a stem or other organ in response to light.
Phyllary, phyllaries	Individual bract within an involucre or involucel.
Phylogeny	The study of relationships between different taxa, or groups. Refer to taxonomy.
Pileous	Covered with hair, or furry.
Pilose	Specifically referring to a covering of short, soft fine hairs. Refer to pubescent.
Pinna, pinnae	A single unit, or leaflet, of a pinnate leaf, or the first division of a bi-pinnate leaf, where this first division is itself divided into leaflets.
Pinnate	A compound leaf with leaflets arranged on each side of a rachis or central axis. The rachis is an extension of the petiole. A pinnate leaf may either be paripinnate, with an equal number of leaflets, or imparipinnate, with a terminal leaflet. The term pinnate also refers to how lateral veins are arranged in relation to the midrib.
Pinnatifid	Pinnately lobed with shallow lobes. The term is sometimes used for any pinnately lobed leaf, irrespective of depth.
Pinnatilobate	With lobes arranged in a pinnate manner.
Pinnatipartite	Pinnately divided to about halfway to the midrib.
Pinnatisect	Pinnately divided almost to the midrib.
Pinnule	The secondary or higher division of a compound leaf. In simpler language, a pinnule is any of the ultimate leaflets of a bipinnate leaf.
Pistil	the female organ of a flower that consists of ovary, style and stigma. In syncarpous flowers, the term refers to the whole gynoecium, whereas in apocarpous flowers, the term pistil refers to each separate unit of carpel, style and stigma. See gynoecium.
Placenta	The wall of the ovary to which the ovules or seeds are attached.
Plicate	Pleated or folded, as a folding fan. Many palm leaves are plicate, folded longitudinally with distinct ridges.
Plinerved	Several nearly equal secondary veins arising at or near the base.