Ultrastructural modifications in the apertural intine of Parietaria judaica L. (Urticaceae) pollen during the early stages of hydration

Hydration and activation of the Parietaria judaica L. (Urticaceae) pollen result in ultrastructural modifications in the apertural region. The particularly distinct intine under the apertures forms convex onci that undergo short but significant and reversible changes during the 10 first minutes of pollen grain hydration and activation. Such changes seem to involve the rough endoplasmic reticulum and show that the oncus is a dynamic structure. This confirms the elasticity of the intine and shows a new pattern of activity in this structure during hydration and activation of pollen germination in vitro.     

Structure of the apertural sporoderm of pollen grains inEuphorbia andChamaesyce (Euphorbiaceae)

The tricolporate pollen grains of 38 Mediterranean and Macaronesian species ofEuphorbia L. andChamaesyce S. F. Gray have a special apertural sporoderm not found in the other taxa of theEuphorbiaceae. At the apertural margo the ectexine is thinner because of shorter columellae and the thin, fragmented or even absent foot-layer. Ectexinous granules, mixed with endexinous material, are present near the ora. The endexine is homogeneous and thickened under the colpi (at the end and at the proximity of the end of colpus). Around the ora, the endexine is granulate and lamellar with irregular cavities. The apertural intine presents a characteristic structure with thickenings running along both sides of the colpi. The arrangement and structure of these intinous thickenings depend on the distance from the ora. This special morphology of the intine is present in all taxa studied here. The genusEuphorbia is considered to be the most evolved taxon of this family. The characteristic apertural sporoderm may be an adaptative modification to different physiological conditions, so it may present an apertural mechanism which is more adapted to harmomegathic changes and thus facilitate the germination and the formation of the pollen tube.     

An Unusual Cytoplasmic Component in Euphorbia peplus L. Endosperm

The coenocytic endosperm of Euphorbia peplus contains a complexsystem of flat, tightly-stacked membrane saccules which havea sinuous profile and a smooth or smooth-rough surface. Theyare joined by membrane-to-membrane links. The usual ergastoplasmiccisternae are an integral component of this system which canessentially be regarded as a sui generis from of endoplasmicreticulum.Copyright 1995, 1999 Academic Press Euphorbia peplus, TEM, ultrastructure, endosperm, endoplasmic reticulum, cell organelles     

八种国产大戟属植物的核型报道

8种大戟属Euphorbia L．植物的核型分析结果表明,大戟属不同亚属的染色体基数与其形态变 异的复杂性有一定关系。地锦草亚属subgen．Chamaesyce 3个种染色体基数分别为x=8,9,11;一品红 亚属subgen．Poinsettia两个种染色体基数均为x=7,分别为四倍体和八倍体;乳浆大戟亚属subgen． Esula 3个种,染色体基数分别为x=7,10,10。根据以前学者发表的资料分析,一品红亚属和大戟亚属 Subgen. Euphorbia的染色体基数是很稳定的,分别为x=7和x=10;通奶草E．hypericifolia为x=8 的四倍体,它不仅有染色体整倍性的变异,还有异基数性的变化。结合以前学者的研究,笔者支持x= 10为大戟属的最原始基数的观点。齿裂大戟E．dentata和通奶草具不同的染色体倍性,猫眼草E． esula的细胞染色体数目观察证实了我国存在四倍体的居群,与欧洲和北美的植物构成一个典型的多倍体复合体。     

Karyotypes of eight species of Euphorbia L. (Euphorbiaceae) from China

In this paper, eight species of the genus Euphorbia L. were cytologically studied. The three species of the subgenus Chamaesyce Raf., E. hirta, E. humifusa and E. hypericifolia, had chromosome numbers of 2n = 18, 22 and 32, with their basic chromosome numbers being x = 9, 11 and 8 respectively. The two species of the subgenus Poinsettia (Grah.) House. E. dentata, with 2n=28, a tetraploid, and E. cyathophora, with 2n= 56, a octoploid, had both the basic chromosome number of x= 7. The three species of the subgenus Esula Pers, E. lathyris, E. helioscopia and E. hylonoma, had chromosome number of 2n= 20, 42 and 20, with their basic numbers being x= 10, 7 and 10 respectively. The basic chromosome number of x = 8 is new for E. hypericifolia, in which x = 7 was previously reported. This indicates that this species had both ploidy(2n = 4x = 28, 8x = 56) and dysploidy(x = 7, 8) variations. In E. dentata, there occurred also ploidy variation (2n = 2x, 4x and 8x). A tetraploid cytotype of E. esula was found in China, its diploid cytotype and hexaploid cytotype being previously reported in North America, the Iberian Peninsula and some other European areas. Based on our results and those previously reported, we support the viewpoint that x＝10 may be the original basic chromosome number of Euphorbiaand discuss the role of polyploidy and dysploidy in the speciation and evolution of this genus     

Functional andromonoecy in Euphorbia (Euphorbiaceae)

The occurrence of cyathia containing staminate flowers but lacking a pistillate flower was studied in 17 species of Euphorbia. Male cyathia were found in the majority of species studied (88.2%) giving functional andromonoecy. In the male cyathia, the pistillate flower is generally totally absent, but sometimes a vestigial pistillate flower with a non-functional ovary is present. The proportion of male cyathia varied at both the population and species level. The position of male cyathia within the inflorescence showed a constant pattern among species: the proportion of male cyathia decreased from the first to the last levels of the pleiochasia. In general, perennial species had significantly higher proportions of male cyathia than annual species (mean 20 and 2.3%, respectively). In annual species there was a trend for production of male cyathia only in the first level of the inflorescence, whereas in perennials production up to the fourth level of the inflorescence was usual. Functional andromonoecy is common in Euphorbia and represents a new sex segregation in the genus. The selective forces causing this secondary sex segregation in Euphorbia, such as improved pollination or increased outcrossing, are discussed.     

Phylogenetics and the evolution of major structural characters in the giant genus Euphorbia L. (Euphorbiaceae)

Euphorbia is among the largest genera of angiosperms, with about 2000 species that are renowned for their remarkably diverse growth forms. To clarify phylogenetic relationships in the genus, we used maximum likelihood, bayesian, and parsimony analyses of DNA sequence data from 10 markers representing all three plant genomes, averaging more than 16kbp for each accession. Taxon sampling included 176 representatives from Euphorbioideae (including 161 of Euphorbia). Analyses of these data robustly resolve a backbone topology of four major, subgeneric clades--Esula, Rhizanthium, Euphorbia, and Chamaesyce--that are successively sister lineages. Ancestral state reconstructions of six reproductive and growth form characters indicate that the earliest Euphorbia species were likely woody, non-succulent plants with helically arranged leaves and 5-glanded cyathia in terminal inflorescences. The highly modified growth forms and reproductive features in Euphorbia have independent origins within the subgeneric clades. Examples of extreme parallelism in trait evolution include at least 14 origins of xeromorphic growth forms and at least 13 origins of seed caruncles. The evolution of growth form and inflorescence position are significantly correlated, and a pathway of evolutionary transitions is supported that has implications for the evolution of Euphorbia xerophytes of large stature. Such xerophytes total more than 400 species and are dominants of vegetation types throughout much of arid Africa and Madagascar.     

Two new species of Euphorbia subsp. Euphorbia (Euphorbiaceae) from east and northeast Somalia

Two small species of succulent, spiny Euphorbia are described as new, both with limited distributions, E. ammophila from the coastal plain of eastern Somalia, and E. densispina from the mountain ranges of the northeast.     

Phytochemical analysis and evaluation of antioxidant and anti-acetylcholinesterase activities of Euphorbia dendroides L. (Euphorbiaceae) latex

The aim of this study was to evaluate the antioxidant and anti-acetylcholinesterase properties and phytochemical constituents of the latex from Euphorbia dendroides L. (Euphorbiaceae) growing wild in Sicily. Phytochemical analysis revealed that into E. dendroides latex the triterpenoids were the most abundant among the identified compounds. Furthermore, a high content of polyphenols mainly as phenolic acids, was found. The antioxidant and free-radical scavenging properties, by several in vitro assays such as DPPH, TEAC and FRAP, have been evaluated. The results showed that E. dendroides latex has significant antioxidant activity, as measured by DPPH assay (2927.01?±?98.03 µmols of Trolox equivalent (TE)/100g FW). Reactivity towards ABTS radical cation and ferric-reducing antioxidant power (FRAP) values were 7580.95?±?97.65 µmols of TE/100g FW and 4383.13?±?95.30?μmol of TE/100g FW, respectively. The latex exhibited also significant inhibition of acetylcholinesterase activity with an IC₅₀ value of 4.46 µg/mL (C.L.?=?2.002–9.947). Furthermore, Brine shrimp (Artemia salina) cytotoxicity bioassay showed that the larvae viability was significantly affected at higher concentrations than those capable to induce significant antioxidant and anti-acetylcholinesterase effects (LD₅₀ 25 µg/mL). The results suggest that polyphenols and terpenoids can contribute significantly to antioxidant and anti-acetylcholinesterase activities of E. dendroides latex.     

New pair-spined species of Euphorbia (Euphorbiaceae) from Somalia

Eighteen new species of Euphorbia subgenus Euphorbia are described and their relationships discussed. All are endemic to Somalia, with limited distributions in the northern Regions. One, E. phillipsioides , has been identified mistakenly for some time as E. phillipsiae , which is shown to be conspecific with E. golisana. E. xylacantha , considered by N. E. Brown to be synonymous with E. monacantha , is reinstated as a distinct but variable species.     

On the unusual distribution pattern of leaf sclereids in Androstachys johnsonii Prain (Euphorbiaceae)

The leal sclereid pattern is described and interpreted as consisting of two types: fibre–like idiolibrosclereidsi in loose bundles above the veins bill often with branches protruding into the intercostal areas and highly branched idioblaslic sclereids lying in the mesophyll but with branches associated with die veins. The significance of "this pattern is discussed in relation to taxonomy and to oilier leal sclereid patterns in angiosperms.     

A new arborescent Euphorbia (Euphorbiaceae) from northern Somalia

Euphorbia spissa, sp. nov., a tree known from a single population on a rocky limestone slope in northern Somalia, is described and illustrated. The species is compared with the widespread E. tirucalli, as well as with E. cameronii and E. bariensis (endemics in Somalia), E. arbuscula (endemic on Socotra), and E. uzmuk (endemic in northern Yemen).     

Seed morphology of Iranian annual species of Euphorbia (Euphorbiaceae)

Euphorbia (Euphorbiaceae) is one of the largest and most diversified cosmopolitan genera of flowering plants. South‐west Asia is a major centre of diversity and contains c. 65 annual species, 35 of which occur in Iran. In this article, the seed morphology of all Iranian annual species was studied, including E. aulacosperma and E. rhabdothosperma, both new records for Iran. Quantitative and qualitative macro‐ and micromorphological features of seeds and caruncles were investigated using stereomicroscopy and scanning electron microscopy. Caruncle characters (shape, size, colour) and seed characters (shape, size, colour, ornamentation) are often constant and useful in identification and classification. An identification key and scanning electron micrographs are provided for all known Iranian taxa. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 167 , 212–234.     

Preliminary results on the ichthyocidal properties of Euphorbia ingens (Euphorbiaceae)

Euphorbia ingens belongs to the family Euphorbiaceae, which includes a variety of latex-producing plants, the majority of them having ichthyocidal properties (Coates-Palgrave 2000). Tests to determine the degree of virulence of E. ingens latex used Cyprinus carpio and Xenopus laevis as the main test organisms. Fish and frogs were exposed to various concentrations of latex to determine the concentration lethal only to the fish. The same concentrations were then used to determine the stability of the latex, by exposing fish in tanks with and without biological filtration. The breakdown period varied, with it breaking down quicker with biological filtration than without it. Once the stability of the latex within a system was determined, crabs, aquatic snails, frogs and fish were all simultaneously tested in a tank at the same concentration as before. Within 12 hours all the fish and half the frogs died, whereas the crabs and snails appeared not to suffer any detrimental effects. The poison degraded and became harmless to fish within 48 hours. Thus, the latex of Euphorbia ingens is a temporarily effective ichthyocide when applied in the correct concentrations.     

Euphorbia gokakensis sp. nov. (Euphorbiaceae) from sandstone formations in Karnataka,India

Euphorbia gokakensis, a new succulent species of Euphorbiaceae, is described from the Belgaum district of Karnataka, India. The new species belongs to Euphorbia subgen. Euphorbia, and closely resembles Euphorbia caducifolia Haines. However, it is distinguished by its characteristic dwarf habit forming a compact cushion that hardly exceeds 50 cm in height.     

Evolutionary bursts in Euphorbia (Euphorbiaceae) are linked with photosynthetic pathway

The mid‐Cenozoic decline of atmospheric CO₂ levels that promoted global climate change was critical to shaping contemporary arid ecosystems. Within angiosperms, two CO₂‐concentrating mechanisms (CCMs)—crassulacean acid metabolism (CAM) and C₄—evolved from the C₃ photosynthetic pathway, enabling more efficient whole‐plant function in such environments. Many angiosperm clades with CCMs are thought to have diversified rapidly due to Miocene aridification, but links between this climate change, CCM evolution, and increased net diversification rates (r) remain to be further understood. Euphorbia (～2000 species) includes a diversity of CAM‐using stem succulents, plus a single species‐rich C₄ subclade. We used ancestral state reconstructions with a dated molecular phylogeny to reveal that CCMs independently evolved 17–22 times in Euphorbia, principally from the Miocene onwards. Analyses assessing among‐lineage variation in r identified eight Euphorbia subclades with significantly increased r, six of which have a close temporal relationship with a lineage‐corresponding CCM origin. Our trait‐dependent diversification analysis indicated that r of Euphorbia CCM lineages is approximately threefold greater than C₃ lineages. Overall, these results suggest that CCM evolution in Euphorbia was likely an adaptive strategy that enabled the occupation of increased arid niche space accompanying Miocene expansion of arid ecosystems. These opportunities evidently facilitated recent, replicated bursts of diversification in Euphorbia.     

A new spiny Euphorbia (Euphorbiaceae) species from northeast Somalia

A small succulent, spiny Euphorbia is described as a new species, E. patentispina , endemic to Somalia, with a limited distribution in the northeast region of Bari. Its relationship to other species of the same group—those producing subsessile capsules and a single spine from each spine shield—occurring in northern Somalia is discussed.     

The occurrence of C(2) photosynthesis in Euphorbia subgenus Chamaesyce (Euphorbiaceae)

This study investigated whether Euphorbia subgenus Chamaesyce subsection Acutae contains C(3)-C(4) intermediate species utilizing C(2) photosynthesis, the process where photorespired CO(2) is concentrated into bundle sheath cells. Euphorbia species in subgenus Chamaesyce are generally C(4), but three species in subsection Acutae (E. acuta, E. angusta, and E. johnstonii) have C(3) isotopic ratios. Phylogenetically, subsection Acutae branches between basal C(3) clades within Euphorbia and the C(4) clade in subgenus Chamaesyce. Euphorbia angusta is C(3), as indicated by a photosynthetic CO(2) compensation point (Г) of 69 μmol mol(-1) at 30 °C, a lack of Kranz anatomy, and the occurrence of glycine decarboxylase in mesophyll tissues. Euphorbia acuta utilizes C(2) photosynthesis, as indicated by a Г of 33 μmol mol(-1) at 30 °C, Kranz-like anatomy with mitochondria restricted to the centripetal (inner) wall of the bundle sheath cells, and localization of glycine decarboxlyase to bundle sheath mitochondria. Low activities of PEP carboxylase, NADP malic enzyme, and NAD malic enzyme demonstrated no C(4) cycle activity occurs in E. acuta thereby classifying it as a Type I C(3)-C(4) intermediate. Kranz-like anatomy in E. johnstonii indicates it also utilizes C(2) photosynthesis. Given the phylogenetically intermediate position of E. acuta and E. johnstonii, these results support the hypothesis that C(2) photosynthesis is an evolutionary intermediate condition between C(3) and C(4) photosynthesis.     

Laticifer starch grain morphology and laticifer evolution in Euphorbia (Euphorbiaceae)

The micromorphology of starch grains in the nonarticulated laticifer was examined in 200 taxa of succulent and nonsucculent Euphorbia. Rod, spindle, osteoid, discoid and intermediate shapes were found in latex. These unusual starch grain shapes are assumed derivatives from more rounded grains present in other angiospermous cells. Unbranched, rod–shaped grains were present in latex of annual and perennial herbaceous taxa. Spindle, osteoid, and discoid shapes, often branched, occurred in xerophytic, succulent taxa. Leafy taxa in several subgenera possessed rod–shaped grains. Taxa of the primitive subgenus, Esula , possessed the shortest rod–shaped grains derived from rounded grains common in parenchyma. Length of rod–shaped grains increased through herbaceous subgenera and culminated in Poinsettia where grain length may be extremely great. Dwarf or shrubby succulents with thickened roots have osteoid grains. Shrubby or arborescent coralline and cactiform species, specialized taxa, possessed large branched grains. Grain morphology of Euphorbia was compared with that from latex of other genera of the Euphorbiaceae. These in–depth analyses of laticifer plastids demonstrates the applicability of starch grain morphology for interpreting the progressive evolution of the nonarticulated laticifer as a cell type within the genus Euphorbia.