Trianthema portulacastrum L. - AIZOACEAE - Dicotyledon

Common name : Horse purslane, carpet weed
Common name in Hindi : Santhi, patharchatta

Habit - © Pierre GRARD - Cirad Opposite and unequal leaves - © Pierre GRARD - Cirad Small white flowers - © Eang KHUON - RUA Capsule and seeds - © Pierre GRARD - Cirad Botanical line drawing - © -

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Diagnostic characters Biology Ecology and distribution Nuisance Weed control Botany Uses/Remark References

Diagnostic characters :

Horse purslane is an annual fleshy plant, prostrate to weakly raised, with numerous basal ramifications. It can reach 30 in 50cm in height.
The stem is finely hairy on faces exposed to the light.Leaves are simple, entire but of uneven size (a great in front of a small one). Twigs and flowers develop always in the base of the small one. The lamina is ovate and fleshy.
Flowers are solitary, sessile and with star shape, white to pale pink and very small.
Fruits are small capsules; seeds kidney-shaped, brown to black.

Biology :

Horse purslane is an annual or perennial species. It propagates by seeds and by fragments of stem which propagate from cuttings very easily. Two biotypes of T. portulacastrum occur in India. Typical description refers to red biotypes that form larger plants and reddish stems with long internodes; and green and smaller type, with shorter internodes, flowers with green bracts and pods, and white sepals. The red type is more abundant, but the green one appears earlier in the season.

Ecology and distribution :

T. portulacastrum is cosmopolitan, with no known centre of origin and widespread in Southeast Asia, tropical America and Africa. Common from sea level, in the sandy and muddy coastal zones, up to near 800 m. In India, both red and green biotypes grow best under partial shade and thrive in neutral to alkaline soils that are low in organic matter.

Nuisance :

It occurs in cultivation fields, waste places, roadsides, lawns and gardens. Occasionally, it is found in perennial crops and pastures. It is common in India in upland rice and in vegetable farming’s.

Weed control :

- Cultural
It may be difficult to control by tillage because of ready regrowth from cut stems.
Gibbago trianthemae, the causal agent of leaf spot on T. portulacastrum, was isolated from diseased plants collected in Texas, USA. Plants sprayed with conidia were killed within 9 days. In host-range studies, the fungus was pathogenic only to T. portulacastrum. This fungus may be a useful agent for the biological control of this species.
- Chemical
Propanil at 2 kg ha-1 applied two weeks after rice emergence or application of 2_4-D at 500 g/ha or Almix at 4g/ha.

Botany :

Rather fleshy plant, prostrate to erect and very branched, developing in mats.
Cylindrical, full, fleshy, finely pubescent on the face exposed to the light. Stems can achieve until 1 m of length. It is often tinged of purple. The ramifications are in the axils of the small leaves of every pair.
Simple, opposite with petiole expanded at the base. Stipules interpetiolar surmounted of a great tooth in the middle. The pair of leaves is very unequal in size. The great one long from 2 to 4,5cm and wide from 1 to 3,5cm, is carried by a petiole from 1 to 2cm. Its lamina is elliptic to obovate, with the tip very broadly rounded, base acute and shortly decurrent on the upper part of the petiole. Margin is entire and slightly wavy. The small leaf is almost sessile, more or less with elliptic shape. Faces are hairless, except for the minutely papillate-denticulate margins.
Solitary flowers, sessile, in the armpit of the small leaves and more or less inclusive in the petiolar sheath. Calyx with 5 sepals ovals to lanceolated. Corolla simple, with 5 white petals and pink-purple inside, lengths from 3 to 5mm, presenting a dorsal mucro sub apical. 15 - 20 stamens inserted at the top of the calyx tube.
Capsule dehiscent, from 4 to 5mm in length, with a single awn at the tip, opening around the middle, containing 2 to 8 seeds.
Kidney-shaped, in spiral ended by a beak, 2mm in diameter. The tegument is tuberculate, reddish, brown to black.
Cotyledons elliptic lanceolated, petioled, of uneven size, a from 12 to 16mm in length and 3 to 4mm wide, the other one from 10 to 12mm in length and 2 to 3mm wide, hairless and fleshy.
First leaves are opposite, simple, presenting the peculiarity to have a small leaf in front of a big one, in alternation. The petiole is brief, expanded at the base. The lamina is elliptic rounded, hairless, fleshy. An interpetiolar stipule decorated in the middle of an expansion acuminated from the second pair of leaves.

Uses/Remark :

References :

- Galinato M., Moody K., Piggin C. M. 1999. Upland rice weeds of South and Southeast Asia. IRRI. Philippines.
- Radanachaless T., Maxwell J. F. 1994. Weeds of soybean fields in Thailand. Multiple Cropping Center Publications. Thailand.

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