Lemna aequinoctialis Welw., Apont.

Freitas, Rafaelle Neves, Silva, Maria Francilene Souza, Paiva, Jousimar Silva, Mayo, Simon Joseph & de Andrade, Ivanilza Moreira, 2017, Taxonomic survey of the Araceae Juss. in the coastal region of Piauí state, northeast Brazil, including the Rio Parnaíba Delta, Iheringia, Série Botânica 72 (3), pp. 341-350 : 343

1. Lemna aequinoctialis Welw., Apont. 578. 1858 [1859].

( Figs. 1 A-C, 2A)

Minute, free-floating aquatic plant. Root one per frond, 0.5-4 cm long, surrounded at the base by a winged root sheath. Fronds 1-5 × 0.5-3 mm, sessile, in groups of 2-3, obovate to lanceolate, chlorophyllous, longer than wide, glabrous, shiny on both sides, apex rounded, base obtuse, margin entire; two papillae present on the upper surface of the frond, one at the base and another near the distal margin of the frond; veins three, one central and two curved laterals. Flower and fruit not observed.

Selected material: Cajueiro da Praia : Boa Vista, 08.XI.2011, Freitas 39, 40 ( HDELTA) . Ilha Grande : Barro Vermelho, 16.III.2012, Freitas 69 ( HDELTA) . Parnaíba : Fazendinha, 09.IX.2011, Freitas 31, 33 ( HDELTA) ; Braço do Rio Igaraçu , 30.XI.2011, Freitas, 43, 44, 45, 58, 59, 60 ( HDELTA) .

Comments: This species, popularly known as “lentilhad’água”, is found along the margins of rivers, streams and lakes, sharing the same environment with other aquatic plants such as Wolffiella spp. , Pistia stratiotes , Eichhornia crassipes and species from the family Poaceae .

It occurs in tropical and subtropical regions around the world ( Landolt 1986, WCSP 2015). In Brazil it occurs in the North (Amazonas), Northeast (Alagoas, Bahia, Ceará, Pernambuco, Piauí, Rio Grande do Norte), Mid-West (Mato Grosso do Sul, Mato Grosso), Southeast (Espírito Santo, Rio de Janeiro), and South (Santa Catarina) ( Coelho et al. 2015). A species which has been introduced to many regions, it occurs mainly in shallow lakes, near farms, and other in areas with human influence, where it can cover most of a water body in a short time via vegetative propagation, and can form communities with Wolffiella lingulata and W. oblonga .

Figures

Figs. 1A-S. Araceae from the coastal region of Piauí.A-C. Lemna aequinoctialis Welw.; A. Habit,side view; B. Habit, seen from above;C. Frond showing three veins; D-G. Lemna valdiviana Phil. D. Habit, side view; E. Habit, seen from above; F. Frond showing single vein; G. Fruit; H-N. Montrichardia linifera (Arruda) Schott. H. Habit; I. Inflorescence; J. Stamen; K. Stigma see from above; L. Female flower in longitudinal section showing ovule; M. Infructescence; N. Seed; O-S. Pistia stratiotes L. O. Habit; P. Leaf blade seen from above showing venation; Q. Inflorescence; R. Fruit; S. Seed.