Swainsona formosa, Sturt pea, is an Australian ornamental plant belongs to the genus Swainsona. The plant is classified under family Fabaceae. It is one of the Australia's best known wildflowers. Its was named after English botanist Isaac Swainson, famous for its distinctive bloodred leaf-like flowers, each with a bulbous black centre. This black centre is known as "boss". It is native to the arid regions of central and north-western Australia, and its range extends into all mainlands of Australian states with the exception of Victoria. The plant is well adapted to harsh desert conditions such as low rainfall and temperature extremes. Plant grows well in open plains and dry woodlands and is often found in disturbed habitats such as along roadsides. It is the floral emblem of the state of South Australia. The plant is an annual to biennial herb with long roots and creeping stem.

Common names of Swainsona formosa plant
Various workers given different names to Swainsona formosa during time to time. Some of the common names for Swainsona formosa (2). Names of author and years in which the name have been proposed are given below :
Showy Donia (G. Don, 1832), Beautiful Donia (G. Don, 1832), Dampier's clianth (Veitch, 1850), Dampier's Clianthus (Hooker, 1858), Sturt's pea (Adelaide Advertiser, 1858), Sturt pea (de Mole, 1861), Captain Sturt's desert pea (Aspinall, 1862), Desert pea (Anon., 1864), Sturt's desert pea (Tenison-Woods, 1865), Glory flower (Bailey, 1883), Glory pea (Bailey, 1883), Sturt's glory pea (Anon., 1886), Lobster claws (The Garden, 1890), Blood flower (Parker, 1898), Dampier's glory pea (Guilfoyle, 1911), Australian glory pea (Guilfoyle, 1911), Dampier pea (Harris, 1980)

Distribution
The plant is widely distributed to Central and South Australia - from Karratha (Western Australia) to New South Wales and Queensland, and from Alice Springs (Northern Territory) to South Australia - in all mainland Australian states except Victoria. It has been introduced to England in 1855.

Habitat
Sturt's Desert Pea is well adapted to life as a desert plant. It grows in arid woodlands and on open plains, often as an ephemeral following heavy rain. Most forms of the plant are low-growing or prostrate however in the Pilbara region of north-western Australia varieties growing as tall as 2.0 m have been observed.

History of Sturt pea
Specimens of Sturt pea were first collected by William Dampier who recorded his first sighting on 22 August 1699. These specimens are today in the Fielding-Druce Herbarium at Oxford University in England.

Legend of Sturt pea
The flower is referred to as the "flower of blood" by some Koori groups. This title came from the legend that tells of young woman who escaped marriage to n elderly gentleman by eloping with her younger lover. The shunned man and some of his friends tracked the couple down after some years and killed them both, as well as the relatives with whom they had lived. Some time later, the old man returned to the place
where he had killed the lovers and found the ground covered with the scarlet flowers that we known as the Stuart's desert pea.

Taxonomy of Sturt pea
On a number of occasions the systematic position of Sturt pea plant has been changed. It was initially treated in the 18th century in the genus Clianthus as Clianthus dampieri, and later became more widely known as Clianthus formosus (formosus is Latin for "beautiful"). However it was later reclassified under the genus Swainsona as Swainsona formosa, the name by which it is officially known today.

Morphological description
Swainsona formosa is classi?ed as a day-neutral annual plant. In general, dayneutral plants blooms when they reach a certain morphological maturity, regardless of day length and photoperiod. It is one of the most showy winter annuals. The plants have well developed branching system and grow up to a height of 80.0 cm.

Root
The plant also has a long tap root that improves its ability to access water in an arid environment.

Stem
The stem is herbaceous and its growth is prostrate. Stem growth is slow and it develops horizontally. Colour of the stem is green. At the time of flowering erect stem growth is clearly visible and flowering starts at these stems. The flowering stem is erect, 50-150(-200 cm) long, greyish green to reddish.

Leaf
The pinnate leaves are grayish green and can have as many as 15 leaflets. They are covered with fine white hairs that reflect sunlight and help the plant maintain a suitable temperature under the hot desert sun. The leaves and stems are covered with downy hairs. The leaves are odd-pinnate, up to 30 cm long, petiolate, the leaflets with short petiole or sessile, elliptic, greyish green, downy with striking midrib.

Flower
The inflorescence is 6-9-flowered, up to 30 cm long, the flowers are 4-9 cm in length and grow in clusters of vertical stalks, the petals are usually blood red or scarlet, rarely yellowish or whitish, with a glossy black swelling at the base of the petals. The flower itself has the shape of a parrot's bill or a lobster's claw and is very pretty in appearance. The flowers are quite large, 6.0 to 8.0 cm across and are borne in clusters of 4 to 6 flowers. The flowers are pendulous and dark crimson in colour with a raised black base which resembles the eyes. The colour can range from white to deep pink and, in rare cases, a bicolor form in which the upper petal is scarlet and the other petals are white tipped and edged with scarlet. Most varieties, but not all, have a distinctive black swelling called a boss at the base of the top petal. Flowers mainly from January to July. Flowers are bird-pollinated in the wild.

Fruit
The fruit is a legume, about 5.0 cm long, slightly curved and each yield 50 or more flat, kidney-shaped seeds at maturity.,

Seed
The seeds have a very hard outer coating that resists germination unless they are scratched or soaked in water. They often germinate quickly after heavy rain.

Cultivation
It is often considered difficult to cultivate, but if treated carefully, its successive produce of exquisite flowers makes it a rewarding and worthy plant to grow. Swainsona formosa makes a very attractive garden plant if given the right conditions. It is a short-lived perennial plant in its native habitat, but most gardeners treat it as an annual. Established plants can tolerate light frost. It can be easily grown from seed, but the seeds should be scoured or nicked first to promote germination. Because of the unpredictability of water, this eye-catching annual takes advantage of rains by germinating, growing and seeding quickly. In its natural habitat it then dies, leaving behind hard-coated seeds which are slowly worn down and cracked by high temperatures or worn with sand abrasion in readiness for germination with the next rains.

It can also be propagated by following methods: 1. Seeds 2. Tissue culture. 3. Grafting

It is sometimes grafted onto another legume such as the New Zealand native, Clianthus puniceus, to make it easier to grow in humid conditions.

In Australia
It is generally grown in the hot, arid, sandy areas of Australia, and is sensitive to root disturbance. Plant is able to survive in harsh conditions. It does not grow easily as a garden plant. The Desert Pea enjoys good drainage for healthy growth. It does not like wet roots, unless its natural conditions can be replicated by creating built-up beds of sandy loam with full sun and sparse watering. The main flowering period is from September to December but flowering can occur all year round. Some plants have two or more flowering periods over a year. Seeds are present on plants from December to April, but may persist on the plant for much longer period. In natural conditions plant grows in sandy and well drained soil. Flowering and seed production varies markedly from year to year which is mainly influenced by climatic conditions.

In India
The plant enjoys healthy growth and good flowering in well manure, drained soil and likes sunny place. In excessive rainfall areas such as Kolkata, it fails to perform well. It grows exceedingly well under climatic condition prevailing in Delhi. It is recommended that before sowing, the hard seed coat may be punctured at one end for the better germination. Sowing is done at September-October, preferably in situ. Seeds may be sown in 7.0 cm nursery pots and the plants are transplanted along with soil without disturbance in a mound or un-glazed terracotta pot or a hanging basket to ensure excellent drainage. Rain protected area should be selected for the better performance of the plant. An ideal spot would be in the shelter of tree in a very well-lit position. Full sun is particularly important in winter season. Special care should be taken at the time of irrigating the plant so that water remains off the leaves as much as possible, particularly in humid climates. Plants need staking. Blooming takes about 3 1/2 months.

Common diseases and its prevention
Although much admired, these plants are notoriously hard to grow outside their natural desert environment as they are prone to fungal diseases and root rots.
Three fungi are responsible to cause root rots on Swainsona formosa: 1. Pythium sp., 2. Rhizoctonia sp. 3. Fusarium avesaeum.

All root rots produce similar symptoms of stunting, yellowing foliage, wilting and ultimately the death. Swainsona formosa suffers from infection during the early stage of production; large established plants do well in field beds, provided soil is well drained and irrigated properly. Seedlings have slowly developing root systems that are highly prone to root rot.

Viruses can be destructive; the risk of virus infection is higher when Clianthus seedling shared green house space with a variety of other crops. The basis for preventing root rots is sanitation and providing a good culture for the plants. Drainage is critical, irrigate to maintain proper moisture, but do not leave soil saturated for extended periods. Chemical fungicide drenches or biological fungicides such as Root Shield or Soil Guard are also helpful.

Light is so essential for plants that they have two different systems to take advantage of it, explains Meng Chen, an assistant professor of biology at Duke University.

A familiar system - chloroplasts - turn sunlight into fuel via photosynthesis. The photosynthetic pigment inside chloroplasts, chlorophyll, is where the green colour comes from. And then there is a system of light-sensitive proteins called photoreceptors that use light as information and direct plant development and growth. One of the things the plant does with that information is control how it makes chloroplasts. "The greening process is completely dependent on the presence of light.
However, how light triggers the making of chloroplasts is still unknown," Chen said. A team of researchers from Duke University and the Salk Institute for Biological Studies has found a central part in the machinery that turns plants green when they sense light. The team has identified a key intermediary between the light system for information and the light system that makes fuel. The hope is that this knowledge will help researchers use a plant's own photo-sensory systems to increase agricultural yields or improve the photosynthesis of biofuel crops. It is published in Cell.

Plants have an array of photoreceptors that are tuned to different wavelengths of light. One type, called phytochromes, are sensitive to red and far-red light and play a major role in the making of chloroplasts and the growth of the stem, said Chen. One of the first things that happen when the plant detects light is that these phytochromes move from the cell's cytoplasm to its nucleus, where the genes are kept. The photoreceptors gather in discrete spots known as phytochrome nuclear bodies. In an earlier study, Chen had found that the size and number of phytochrome nuclear bodies was directly related to light intensity. Chen ran genetic screens for mutants with abnormal phytochrome nuclear bodies. He identified a new gene, hemera, that seems to be required for both the localization and the signaling of phytochrome. It is present in all land plants studied so far, according to a Duke University press release. Mutant plants without hemera were found to have dramatically reduced sensitivity to red and far-red light, they failed to develop chloroplasts, were albino, and died while still only seedlings.