Ludwigia L.

Rocha, Amanda Macêdo & Melo, José Iranildo Miranda de, 2020, Diversity and distribution of Ludwigia (Onagraceae) in Paraíba State, Northeastern Brazil, European Journal of Taxonomy 639, pp. 1-24 : 5-6

Genus Ludwigia L.

Description

Herbs erect or prostrate, subshrubs to trees, terrestrial or aquatic plants; branches pubescent to glabrescent. Leaves alternate, generally sessile to subsessile; stipules generally lacking or reduced. Flowers solitary, axillary, pedicellate or sessile; bracteoles absent or conspicuous, normally 2, near the base of hypanthium; calyx 4–5-merous, dialysepalous, green or reddish, persistent; corolla 4–5–(6)-merous, dialypetalous, yellow or white, deciduous; androecium isostemonous or diplostemonous, disposed in two series, epipetalous shorter than the episepalous, stamens inserted at the base of the epigynous disk together with the petals; hypanthium not extended above the ovary, cylindrical or angular, 4–5-carpellar, 4–5-locular, ovaries numerous, placentation axial, stigma capitate, globose, slightly lobular, the number of lobules corresponds to the number of locules; nectariferous disk generally plain or convex, on the ovary, nectary depressed, covered with indumentum of white trichomes. Fruit a capsule. Seeds small, numerous, uni- or pluriseriate in each locule, free or embedded in endocarp, generally with inconspicuous raphe, in some sections it may be expanded and equal in size to the body of the seed, or rarely expanded and wing-shaped ( Ludwigia sect. Arborescentes Zardini & P.H.Raven ).

Distribution

The genus Ludwigia is pantropical. It is the only genus of the subfamily Ludwigioideae , composed of 83 species grouped in 23 sections, considered the most distinct genus of Onagraceae . Ten sections are distributed in South America, five in Africa, three in North America, three in Asia and two are not restricted to any continent. Main diversity centers are South America and North America ( Wagner et al. 2007; Pesamosca & Boldrini 2015).

Habitat

Specimens of Ludwigia were mainly collected from humid, flooded and aquatic environments ( Fig. 2 ).

Note

In Brazil, species vernacular names are ‘cruz-de-malta’ or ‘pimenta-d’água’.

Key to Ludwigia species recorded in the Paraíba State, Brazil

1. Leaves petiolate, leaf blade orbicular; petals white with yellow spot at the base .............................. ..................................................................................................... L. helminthorrhiza (Mart.) H.Hara

– Leaves subsessile to sessile, leaf blade elliptical to lanceolate or oblong-lanceolate to lanceolatelinear; petals entirely yellow (golden yellow or pale) ...................................................................... 2

2. Flowers pentamerous sometimes hexamerous; endocarp horseshoe-shaped ..................................... ............................................................................................................... L. leptocarpa (Nutt.) H.Hara

– Flowers tetramerous; when present, endocarp is never horseshoe-shaped ....................................... 3

3. Petals with emarginate apex; raphe inflated, with diameter equal in size to the body of the seed ................................................................................................... L. octovalvis (Jacq.) P.H.Raven

– Petals with acute or attenuate apex; raphe non-inflated, with diameter narrower than the body of the seed ................................................................................................................................................... 4

4. Fruits cylindrical; seeds usually pluriseriate and not embedded in the upper part of capsule, and uniseriate and embedded in endocarp in the lower part of capsule .................................................... ............................................................................................................. L. hyssopifolia (G.Don) Exell

– Fruits tetrangular; seeds all pluriseriate and not embedded in endocarp .......................................... 5

5. Leaf blade chartaceous; high nectariferous disk; capsule obconic ............ L. nervosa (Poir.) H.Hara – Leaf blade membranaceous; plain nectariferous disk; capsule oblongoid ...... L. erecta (L.) H.Hara.

Figures

Fig. 2. Environments where species of Ludwigia L. were detected in the studied area, Paraíba State, Brazil. a. Açude Boqueirão, Boqueirão. b. Fazenda ABA, Passagem. c–d. Cachoeira do Pinga, Lagoa Seca. e–f. Afloramento granítico, Puxinanã. g. Monteito. h. Santa Luzia. i. Serra do Jatobá, Serra Branca. j. Parque Estadual Pedra da Boca, Araruna. Photos: a–h = A.M. Rocha, i–j = F.K.S. Monteiro.