Pea Family — Fabaceae
|Silvery oxytrope, Oxytropis arctobia.|
Formerly known as Leguminosae, this cosmopolitan family of 13,000 species contains the legumes – vital food plants, such as peas, beans, lentils, soybeans, peanuts, alfalfa, and liquorice. There are two kinds of flower produced by species in the Fabaceae: regular – whereby parts of the flower are similar in size and shape – and irregular – parts of the flower are of varying shapes and lengths. Sixteen species are found in the Arctic, belonging to five genera: milk-vetches, Astragalus, liquorice-roots, Hedysarum, beach peas, Lathyrus, lupines, Lupinus, and oxytropes, Oxytropis.
General Information and Anatomy
All Arctic Fabaceae have irregular flowers composed of five sepals and five petals that vary in size and shape. The upper and largest petal is called the "banner" petal; two similar, lateral petals are the "wing" petals; and the lower, boat-shaped petal, called the "keel," is actually two fused petals. The ten stamens are oddly shaped as well – nine are united, while the tenth grows freely. The fruits are called legumes and resemble a typical garden pea pod.
There is one deadly, but attractive, plant: the arctic lupine, Lupinus arcticus. Even though its seeds resemble peas, they are lethally toxic. Its flowers are blue and white; its distinct leaves are palmately compound and bear soft, downy hairs underneath. The arctic lupine is endemic to the Arctic Cordillera.
The oxytropes, Oxytropis sp., have flowers that are arranged in head-like clusters atop leafless stems. Their leaves are pinnately compound and arise from a stocky tap root. Aside from their naked flower stems, oxytropes can be distinguished from the milk-vetches by examining the keel petals – those of Oxytropis are tipped with a sharp tooth. The arctic oxytrope, O. arctica, is ubiquitous on the dry soil and open tundra of the Central Arctic islands, where it is endemic. Its flowers are sweetly scented and dark purple; a distinct white marking on the banner petal probably functions to guide their primary pollinators, bumblebees, as they come in for landing on the lower keel petal. Arctic oxytrope is similar to silvery oxytrope, O. arctobia, but lacks the silver-haired upper leaf surfaces of the latter species. Maydell's oxytrope, O. maydelliana, the most widespread member of this genus, is characterized by its shaggy calyx and legumes – the shagginess results from long, black and white, hairs. Its flowers are pale yellow and grow in groups of five to seven on a short spike.
A single species, the wild beach pea, Lathyrus japonicus, is found along arctic seashores. Beach-peas, like other legumes, are "nitrogen-fixers." They possess structures on their roots that contain special bacteria – these microorganisms extract atmospheric nitrogen and convert it to nitrates. The wild beach pea has pale bluish flowers that are often darker in colour towards the base and its leaves are very tender, light green, and clammy to the touch. The range of this plant is restricted to beaches on arctic mainland shores. It grows in a sprawling manner across the sand and acts to reduce beach erosion.