Abstract
Euphorbiaceae s.l. presents several morphological types of fruits, of which the schizocarp is the most common. The fruits of weed species of Euphorbia graminea Jacq., Euphorbia heterophylla L., Euphorbia hirta L. (= Chamaesyce hirta (L.) Millsp.) and Euphorbia prostrata Aiton (= Chamaesyce prostrata (Aiton) Small) are objects of this study. Inflorescences and fruits in development were collected on the campus of the State University of Maringa (UEM), Brazil, fixed in FAA 50 and glutaraldehyde, dehydrated and sectioned with a rotary microtome according to standard morphology and anatomy techniques. The species present several anatomical similarities, though there are some differences related to the outer epidermis of the ovaries, which is glabrous in E. graminea and hairy in the other species. The ripe fruits present a papilose exocarp and lack trichomes, except for E. hirta. The ovules are anatropous, bitegmic and crassinucellate; the seeds are exotegmic and the embryos are straight.
Highlights
Euphorbiaceae s.l. presents several morphological types of fruits, such as a bacca, coccarium and polospermatium (Spjut 1994) or schizocarp, capsule, drupe or a berry (Barroso et al 1999)
The genus belongs to the large tribe Euphorbieae (Euphorbioideae), which is considered monophyletic on the basis of the inflorescence (Judd et al 2002)
The present research deals with the structure and development of fruits and seeds of selected weed species, with emphasis on: a) the definition of the fruit type of the studied species; b) the discussion about the origin and differentiation of the sclerenchymatous tissue which occurs in the species; c) the evaluation of whether the ovules and seeds of the species present the basic characters of Euphorbioideae and Euphorbieae that were formulated by Tokuoka & Tobe (2002); and d) an analysis to see if there are significant structural differences of the fruits and seeds among the species of Euphorbia and Chamaesyce
Summary
Euphorbiaceae s.l. presents several morphological types of fruits, such as a bacca, coccarium and polospermatium (Spjut 1994) or schizocarp, capsule, drupe or a berry (Barroso et al 1999). The tribe Euphorbieae was divided into three subtribes, of which Euphorbiinae is the largest and nearly cosmopolitan In this subtribe the involucre is made up of five bracts, the male flowers lack a perianth and the female flowers are mostly devoid of a perianth (Webster 1975). The present research deals with the structure and development of fruits (pericarp) and seeds of selected weed species, with emphasis on: a) the definition of the fruit type of the studied species; b) the discussion about the origin and differentiation of the sclerenchymatous tissue which occurs in the species; c) the evaluation of whether the ovules and seeds of the species present the basic characters of Euphorbioideae and Euphorbieae that were formulated by Tokuoka & Tobe (2002); and d) an analysis to see if there are significant structural differences of the fruits and seeds among the species of Euphorbia and Chamaesyce
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