This variation enables the species to germinate under a range of environmental conditions and may contribute greatly to its success as a weed ( Maurya and Ambasht, 1973). It appears that different seed morphs vary in their dormancy and germination requirements. All of these variations in colour and form may be found in the seeds of a single plant ( Holm et al., 1977). Testa colour also varies significantly and can be black and shiny, brown or brownish-green. The seeds exhibit considerable polymorphy some are smooth, some striate, and others possess a raised reticulum. Seeds are able to remain viable for extended periods in the soil seed bank, perhaps for up to 40 years Toole and Brown (1946). (1981), but as many as 50,000–70,000 seeds per plant have been found Mandal and Pal (1990). Average seed production varies between 3000 and 20,000 seeds/plant Korsmo et al. Individuals of this species demonstrate a great deal of plasticity in response to their edaphic and biotic environment, and seed production varies greatly according to these factors. In Europe and America, it is a problem weed in maize, soybean, wheat, barley, potato and all vegetable crops. In addition, it is an important weed of tea and upland rice in Japan, citrus orchards and vineyards in Spain, cotton, soyabean and strawberries in the former Soviet Union, cotton, pastures and peanuts in the USA, rice in Mexico and tobacco in Canada ( Holm et al., 1977). In subtropical regions it is most common in wheat, chickpea, barley, winter vegetables, horticultural gardens, maize, sunflower and soybean. In temperate climates, it is a problem in almost all summer- and winter-sown crops. It is one of the principal weeds of Canada and Europe, and in India, Mexico, New Zealand, Pakistan and South Africa is ranked amongst the six most serious weeds ( Holm et al., 1977). It is a common weed in about 40 crops in 47 countries, being most frequent in sugarbeet, potatoes, corn and cereals. album seems to grow most vigorously in temperate and subtemperate regions, however it is also a potentially serious weed in almost all winter-sown crops of the tropics and subtropics. Seed nearly circular in outline, oval in cross section, sides convex, glossy, black, mean size 1.5 mm x 1.4 mm in diameter, weight 1.2 mg. Fruits is an achene (seed covered by the thin papery pericarp). Flower perfect, small, sessile, green calyx of 5 sepals that are more or less keeled and nearly covering the mature fruit petals 1 stamens 5, pistil 1, with 2 or 3 styles, ovary single-celled, attached at right angles to the flower axis. Inflorescence in irregular spikes clustered in panicles at the ends of the branches. Leaves alternate, simple ovate to rhomboid-oval, uppermost leaves mostly lanceolate, sometimes linear and sessile, glabrous, usually white with a mealy-covering, particularly on young leaves, all leaves densely covered with small, utriculate hairs. Stems erect, branched towards apex, 0.2–2 m tall, glabrous, furrowed, often with red or light-green streaks, branching varies from slight to extensive. Fewer, smaller stomata on upper compared to lower leaf surface ( Srivastava, 1967). Epidermal cells are more or less polygonal in shape. Many branches may emerge from main tap root system. Cotyledons petiole, lanceolate-linear, mealy, bluish-grey with a reddish tinge beneath, 6–12 mm long and 1.5–4 mm broad ( Korsmo et al., 1981). Summary of InvasivenessĪn erect, branched (occasionally unbranched) annual herb, green, more or less coated with white mealy pubescence. album has also been used to treat rheumatism, liver disorders and burns. Leaves and seeds are used in traditional medicine to treat a wide range of disorders and have been used as an anthelmintic, cardiotonic, carminative, digestive, diuretic and laxative. album contains several antinutritional factors such as saponins, phytates and oxalic acid, but these are largely broken down by cooking. It is valued for its high protein content and balanced amino acids with high lysine and methionine contents.
Young leaves and stems are collected from the wild, or grown in home gardens, elsewhere in Africa, Asia and South America. It is also cultivated across the Himalayas and northern India as a leafy vegetable. Hermaphrodite and female flowers develop in non-shattering seed heads with larger seeds than wild plants.
Landraces grown for seed are usually taller than their weedy counterparts (up to 4 m tall) and inflorescences are large, compact, exserted and leafless, often drooping. A very variable cosmopolitan, polyploid weedy complex, with landraces selected in the Himalayan region cultivated as a pseudocereal for seeds.
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