Keys Dictionary

Word	Meaning
Pneumatophore	A specialised breathing root that grows upwards from horizontal roots, usually with lenticels for gas exchange. Such breathing root adaptions enable floodplain specialists to survive seasonal waterlogging, when the soil-water air-space system becomes anaerobic.
Pod	A dehiscent, dry fruit with two valves, or lobes, fused together along seams that split open. Pods may be long and narrow, or more rounded. See legume.
Poikilochlorophyllous	Poikilochlorophyllous species in the Xerophyta genus tolerate extreme dryness by dismantling their photosynthetic processes and losing all their chlorophyll during the prolonged drying phase. Once moisture returns, water uptake through the leaf surface is of first importance for recovery. The plant then resynthesises chlorophyll. This enables the plant to avoid photo-oxidative damage and maintain its photosynthetic capacity, despite long periods of desiccation.
Pollen	The powdery fertilising agent carried in the anthers of flowering plants.
Pollination	The transfer of pollen from an anther to a stigma.
Polygamous	A plant that bears both unisexual and hermaphrodite (bisexual) flowers on the same or on separate plants of the same species.
Polyploidy	Refers the presence of multiple copies of identical or similar chromosome sets in one plant species. This is a heritable condition in plants, and is considered as a major driver in plant evolution.
Precocious	Ripening early or before its time.
Prickle	A hard pointed structure growing on a stem that arise from the epidermis, and not from vascular or woody tissue. Refer to spine.
Primary growth	Growth in an apical meristem.
Protandrous	A flower that sheds pollen before its stigma is receptive, to avoid self-pollination. Male functionally precedes female functionally.
Pseudaril	A structure that resembles an aril but is attached to the endocarp, not to the seed.
Puberulous	Covered with minute hairs or very fine down; finely pubescent.
Pubescent	Covered with short soft hair; downy. Refer to pilose.
Pulvinus	A swollen petiole at the leaf base that facilitates growth-independent movement. Asymmetric swelling and contraction of the pulvinus helps in periodic leaf movement. Pulvini are common in Fabaceae.
Pustulate	With slight blister-like elevations.
Putamen	A hard or stony endocarp.
Pyrene	The fruit-stone within a drupe or drupelet, produced by the ossification of the endocarp, or lining of the fruit.
Raceme	A simple inflorescence in which flowers are borne at equal distances along a single elongated axis, which continues to grow indefinitely. The flowers at the base of the central stem develop first. The flowers can be stalked or sessile (see spike). Compare with cyme and spike.
Racemose	The adjective form of raceme.
Rachilla	The central axes that bears the leaflets of a bipinnate leaf.
Rachis	The portion of the main axis of a compound leaf that bears the leaflets. The petiole ends and the rachis begins at the point of the first leaflets.
Receptacle	A receptacle is the enlarged end of a pedicel, which is the stalk of a single flower. In a compound inflorescence, receptacles are the enlarged ends of peduncles or flower stalks. In a fig, the receptacle wraps around the hundreds of flowers it bears, thus forming the fig.
Recurved	Bent backwards, as in recurved thorns.
Reflexed	Curved backwards or downwards.
Reniform	Shaped like a kidney.
Repand	The margin is uneven or wavy, with shallow undulations. See sinuate margins.
resin	Resin is a hardened or viscous secretion produced by plants in response to injury, protecting the plant from pathogens and insects. Resins may also deter herbivores. Resin is not soluble in water.
Resin	Exudate from a cut or other damage to the plant, that hardens when exposed to air. Resin is not soluble in water, and it is not latex.
Reticulate	Net-veined. When the smallest veins of a leaf are interconnected to give the appearance of a mesh-like net.