Lathyrus L.
(Hitchcock, 1952)
Plants annual or
perennial herbs, with taproots or more commonly rhizomes. Stems erect to
spreading or climbing, angled or winged, unbranched
or branched, unarmed, glabrous or pubescent with nonglandular
hairs. Leaves alternate, even-pinnately compound with
2–10 leaflets (rarely with an extra lateral leaflet along 1 side), the petiole
often expanded or winged, the rachis extended into a conspicuous, unbranched or branched tendril (this poorly developed elsewhere).
Stipules leaflike, with a basal outgrowth or lobe of
tissue on 1 side, this rounded or more commonly triangular, descending or
clasping the stem, the margins otherwise entire or less commonly toothed, the
venation mostly inconspicuous, persistent; stipels
absent. Leaflets oblong to elliptic or linear, the margins
entire, the surfaces glabrous or hairy, pinnately
veined or only the midvein visible (often with 3 main
veins in L. sylvestris).
Inflorescences axillary, racemes or clusters, occasionally reduced to solitary
flowers, the bracts 1–3 mm long, shed early, bractlets
absent. Calyces 5-lobed, the tube bell-shaped, usually oblique, often somewhat
pouched on 1 side at the base, more or less 2-lipped, the lobes subequal or the 3 lower lobes longer than the upper 2,
variously shaped, sharply pointed at their tips, glabrous or hairy. Corollas papilionaceous, pink, red, purple, or white (yellow
elsewhere), lacking conspicuous, contrasting markings near the base of the
banner, the banner with a short, sometimes broad, stalklike
base, the expanded portion obovate to nearly
circular, notched at the tip, sharply curved or bent backward, the wings
narrowly to broadly obovate, shorter than to slightly
longer than the banner, usually curved over or around but not fused to the
keel, the keel shorter than the wings, boat-shaped, curved upward, mostly
tapered to a bluntly or sharply pointed tip. Stamens 10, 9 of the filaments
fused and 1 free nearly to the base, all similar in length or in 2 alternating,
slightly shorter and longer series, the free portions of the filaments slender,
but usually broadened toward their tips, the anthers small, attached at the
base, all similar in size, yellow or occasionally orange. Ovary sessile or very
short-stalked, glabrous or occasionally hairy, the style abruptly curved or
bent upward toward the base, somewhat flattened, hairy on the inner surface
toward the tip, more or less persistent at fruiting, the stigma terminal, short
or somewhat elongate. Fruits legumes, oblong to linear, tapered asymmetrically
to a sharply pointed or more commonly beaked tip, flattened or in a few species
turgid, not or only slightly constricted between the seeds, straight or
slightly curved upward, 2- to numerous-seeded, dehiscing by 2 valves, these green
to brown at maturity, usually twisting spirally after dehiscence. Seeds oblong
to kidney-shaped, nearly circular or somewhat angular in outline, flattened or
not, the surface smooth or wrinkled, olive brown to dark brown, sometimes
mottled. About 160 species, nearly worldwide, most diverse in
temperate regions.
Lathyrus is a member of the tribe Fabeae, which is one of the most economically important
groups in the family and also includes the related genera Lens Mill. (lentil), Pisum L. (garden pea), and Vicia L. (vetch).
Species of Lathyrus
are widely planted for soil cover, green manure, and occasionally for human
food. The seeds of L. sativus
L. (grass pea) are high in protein and it has been cultivated for at least
8,000 years (Smartt, 1990). They are highly drought
resistant and produce a crop when other crops fail completely. The use of the
species as food for humans and fodder for livestock is limited by the presence
of toxic nonprotein amino acids that cause a syndrome
known as lathyrism, one of the oldest neurotoxic
diseases known (Burrows and Tyrl, 2001). Symptoms
include spasms, weakness, paralysis of the legs, and ultimately muscular
atrophy. Lathyrism remains a problem in impoverished
countries where people are forced to subsist on Lathyrus peas for lengthy periods
in times of famine. Curiously, the evolution and divergence of Lathyrus species
has been accompanied by a threefold increase in chromosome size and fourfold
increase in the amount of DNA (Narayan, 1982; Nandini
et al., 1997).