Small Achenes Research Articles

Strategies of diaspore dispersal investment in Compositae: the case of the Andean highlands.

Understanding diaspore morphology and how much a species invests on dispersal appendages is key for improving our knowledge of dispersal in fragmented habitats. We investigate diaspore morphological traits in high-Andean Compositae and their main abiotic and biotic drivers and test whether they play a role in species distribution patterns across the naturally fragmented high-Andean grasslands. We collected diaspore trait data for 125 Compositae species across 47 tropical high-Andean summits, focusing on achene length and pappus-to-achene length ratio, with the latter as a proxy of dispersal investment. We analysed the role of abiotic (temperature, elevation and latitude) and biotic factors (phylogenetic signal and differences between tribes) on diaspore traits and whether they are related to distribution patterns across the Andes, using phylogenomics, distribution modelling and community ecology analyses. Seventy-five percent of the studied species show small achenes (length <3.3 mm) and 67% have high dispersal investment (pappus length at least two times the achene length). Dispersal investment increases with elevation, possibly to compensate for lower air density, and achene length increases towards the equator, where non-seasonal climate prevails. Diaspore traits show significant phylogenetic signal, and higher dispersal investment is observed in Gnaphalieae, Astereae and Senecioneae, which together represent 72% of our species. High-Andean-restricted species found across the tropical Andes have, on average, the pappus four times longer than the achene, a significantly higher dispersal investment than species present only in the northern Andes or only in the central Andes. Small achenes and high diaspore dispersal investment dominate among high-Andean Compositae, traits typical of mostly three tribes of African origin; but traits are also correlated with the environmental gradients within the high-Andean grasslands. Our results also suggest that diaspore dispersal investment is likely to shape species distribution patterns in naturally fragmented habitats.

A New Species of &lt;I&gt;Cyperus&lt;/i&gt; (Cyperaceae) from Andaman and Nicobar Islands, India

Cyperus nicobaricus V.P. Prasad, belonging to the section Diclidium of the genus Cyperus L. is described here as a new species. It is closely allied to Cyperus odoratus L., but differs mainly in its perennial habit, short size of the plant, reduced inflorescence with congested spikelets and smaller achenes. The distinguishing characters are discussed along with a taxonomic key to differentiate it from the closely allied C. odoratus. An image of the type of the new species is also provided, along with its floral characters.

Adaptive variation in vegetative, reproductive and chemical traits of the Mediterranean Silybum marianum L., under desert-adjacent conditions

Adaptive variation of plant species is best evaluated under environmental gradients. Silybum marianum is a native to the Mediterranean basin, distributed continuously along an aridity gradient from northern Israel to the edge of the Negev desert. To elucidate the adaptive significance of traits associated with proximity to the desert and with increasing levels of aridity, we compared northern populations from the mesic Mediterranean end of the aridity gradient with southern, adjacent to the Negev desert populations, from the arid end. The F1 self-progeny of all populations were evaluated under open field conditions. Plants originated from southern populations grew taller and narrower, completed their life cycle earlier, and produced more abundant, smaller achenes, with a higher content of polyphenols, which grew into smaller seedlings. Correlative analysis revealed a latitudinal cline towards the desert, of a longer life cycle, and fewer, heavier, better germinating achenes, which grew into larger seedlings. We concluded that the proximity to the desert was reflected in the appearance of genotypes with improved chances of survival under arid conditions and with higher contents of polyphenols.

Pectis harryi (Compositae: Heliantheae: Pectidinae), a new species from a rock platform in the Departamento de Santa Cruz, Eastern Bolivia

Summary. A new, dwarf perennial species of Pectis (Compositae: Heliantheae: Pectidinae), Pectis harryi, is described and illustrated from the Departamento de Santa Cruz, eastern Bolivia. The new species adds to the increasingly recognised richness of the rock platforms and low granite shield inselbergs (lajas) of the provinces of Nuflo de Chavez and Velasco. The species has had its Conservation Status recorded as CR (Critically Endangered), although the species may already be extinct in the type locality. The species appears relatively isolated within the genus in its dwarf suffruticose habit, solitary, relatively long-pedicellate small capitula and achenes possessing relatively few, barbellate setae; three types of setulae apices are recorded on the achenes. A short key to the species now known from Bolivia is provided. Comparison is made with other perennial species from Brazil and Colombia. Additional problems with Glaziou’s collection localities are highlighted.

Morphometric Analysis of Sunflower (Helianthus annuus L.) Achenes from Mexico and Eastern North America1

Morphometric Analysis of Sunflower ( Helianthus annuus L.) Achenes from Mexico and Eastern North America. Sunflower (Helianthus annuus L.) has played a major role in the evolution of agricultural systems in the Americas. The discovery of ancient domesticated remains from archaeological deposits in pre-Columbian Mexico offers new dimensions to widely accepted viewpoints on the domestication pattern of H. annuus. Although American sunflower populations north of Mexico have been examined extensively, Mexican indigenous domesticated landraces have not been studied in any detail. In this study, we morphologically assessed wild and domesticated sunflower achenes from Mexico and compared them to similar datasets from eastern North America. Additionally, we evaluated the utility of four computer-assisted shape measurements in discriminating between wild and domesticated sunflower achenes (fruits) and compared variation in achene size among modern wild and cultivated populations from both Mexico and the U.S. We found that, of the shape parameters tested, none were informative in distinguishing wild achenes from domesticated varieties. Subsequent size analysis, using conventional parameters of length, width, and thickness, showed that modern wild populations from Mexico had smaller achenes compared to modern populations from eastern North America. Domesticated achenes unearthed from Mexican archaeological sites, however, were significantly larger than the early domesticated specimens recovered from eastern North America. Our methodological results indicate that variation in archaeological sunflower achenes is better described by conventional size parameters rather than computerized shape analysis.

Vegetative and Reproductive Morphology of an Extinct Early Cretaceous Member of Platanaceae from the Braun’s Ranch Locality, Kansas, U.S.A.

Abstract Early Cretaceous platanoid species are presented, based on observations of isolated organs from the Braun Ranch locality, Kansas, and the Yankee Hill I locality, Nebraska. Approximately 500 leaf specimens and 238 infructescence specimens have been studied in detail. The reproductive axis may contain up to 37 sessile, globose infructescences. Fruits are small achenes and lack dispersal hairs. The leaves are typically three-lobed, with basal or suprabasal actinodromous or palinactinodromous venation. Secondary venation is dominantly craspedodromous. Typically, one secondary vein extends into each tooth and is accompanied by tertiary or higher-order veins, which form a series of ascending loops. Tertiary veins are percurrent, with those in the axils of primary-primary and primary-secondary veins forming a V-shaped pattern. Conically inflated petiole bases are hollow and enclose axillary buds. Stipules are triangular and small and are observed only on immature leaves. The repeated and common co-occur...

Fagopyrum pugense (Polygonaceae), a New Species from Sichuan, China

Fagopyrum pugense T. Yu (Polygonaceae, Polygonoideae), known only from Luojishan, Puge County, Sichuan Province, China, is described and illustrated. It is closely related to F. gracilipes (Hemsl.) Dammer ex Diels, but differs in the plants having thicker stems and branches with densely erect-villose pubescence, numerous nodes and short internodes, ovate to cordate leaves that are minutely rugose with small pustules, and small achenes. The karyotype studies were also conducted, and the results are presented.

Morphological Characteristics and Isozyme Analysis of Triploid Achenes Obtained in the F2 Generation of Interspecific Hybrids between Lactuca sativa L. and L. saligna L.

Seven (18%) and 4 (6.2%) individuals from 39 and 65 F2 progenies obtained from the two interspecific FI hybrids between Lactuca saligna L. and L. sativa L. cv. Bronze were found to be spontaneous triploids. The length (mm) and weight (mg) of achenes formed on L. sativa, L.saligna and their F, hybrids were 4.01, 1.04; 2.70, 0.35; and 4.41 mm, 1.33 mg, respectively, and those of achenes obtained from L. saligna × L. sativa was 2.51 mm and 0.29 mg. The size of achenes obtained on the Fj hybrids ranged from 3.3 to 6.2 mm and 0.2 to 2.4 mg. The size of the F2 triploid seeds from the FI hybrids were classified into 2 groups; 5 triploids with small achene (0.7-1.1 mg) and the remaining 6 triploids with even heavier achene than L. sativa (>1.8 mg). The phenotype of 5 isozyme loci studied, Got-l, Pgi-l, Pgi-2, Pdh-1, and Pdh-2, always showed the 4 : 4 : 1 in band intensity in the triploids, which enabled us to analyze the genotypes. When the gene of L. sativa was named 'l' and that of L. saligna, 'g', all triploids were always heterozygous in the 5 isozyme loci, ggl or gll ; this suggests that triploids resulted from a union of a reduced gamete with an unreduced gamete. The triploids from small achenes were ggl in almost all of the five loci, whereas those from the large achenes were gll. Thus, the curious combinations between achene size and the genotypes indicate that the survival rate of individuals with the distorted combination of genes to one of the two parent species is higher than that with the random combination.

Studies in African Cyperaceae 29. Scleria afroreflexa, a new species from western Cameroon

A new rare species, Scleria afroreflexa. is descriped from an upland area (1500 m) of South west Cameroon. It is most similar to S. sheilae Rayn., another rare species only known from one collection from a rocky habitat at 800 m near Yaounde in southeastern Cameroon. S. afroreflexa differs, however, in its more dense inflorescence with reflexed branches, its more hairy leaves, smaller achenes and in its montane habitat. Notes on habitat, ecology, distribution and conservation are given for the two species.

Role of within-individual variation in capitulum size and achene mass in the adaptation of the annual Centaurea eriophora to varying water supply in a Mediterranean environment.

To clarify the adaptive value of variation in capitulum size and achene mass, plants of Centaurea eriophora were studied in a glasshouse and in a natural population. C. eriophora plants consist of a basal leaf rosette from which an erect stem grows, with lateral branches of various orders ending in capitula of different orders. Primary, secondary and tertiary capitula are comparable in size and they produce similar numbers of achenes, which are similar in weight (large achenes). These capitula are formed during April, May and early June, and constitute the normal or primary flowering. Following ripening of tertiary capitula, leaves senesce, but, later during June and the first half of July, a secondary flowering of a variable number of smaller capitula may occur if wet conditions persist for longer than usual. Plants that have almost senesced develop small lateral branches 1-2 cm long bearing a few small leaves and ending in a capitulum about half the diameter of capitula from the primary flowering period. The number of achenes produced in these capitula (small achenes) and their weight are 70 and 30% less, respectively, than those of capitula formed during primary flowering. These reductions appear to result from restricted availability of resources. Large and small achenes have similar dispersal characteristics and possess similar germination potential. However, large achenes produce seedlings that are capable of emerging from greater burial depths, providing the resulting plants with a potential advantage. The normal flowering period coincides with the optimum time of year for flowering and fruiting in the south of Spain, and only if rainfall lasts longer than usual does secondary flowering occur. Secondary flowering extends the normal flowering and fruiting periods, thereby providing a supplementary crop of smaller, yet viable, fruits. It can be considered to be an adaptive response to the unpredictable Mediterranean climate, optimizing the use of available resources.

Achene mass variation in Ericameria nauseosus (Asteraceae) in relation to dispersal ability and seedling fitness

Abstract1. Ericameria nauseosus (Asteraceae) is a highly variable shrub species of western North America, whose achene mass varies sevenfold among subspecies and populations. We examined trade‐offs between seedling fitness and dispersal ability by asking: does greater achene mass reduce dispersal ability, and is this potential disadvantage to large achenes compensated for by increased pappus investment? Does smaller achene mass reduce seedling fitness, and is this potential disadvantage to small achenes compensated for by increased relative growth rate (RGR)?2. Dispersal ability was measured as fall rate in still air, while seedling fitness was measured as dry mass at two ages for 21 populations belonging to nine subspecies.3. Fall rate was positively correlated with achene plume loading−1/2, but because of variation in pappus investment and geometry, both plume loading−1/2 and fall rate were only weakly positively correlated with achene mass. Relative pappus investment did not show a consistent increase with achene mass.4. Seedling dry mass was strongly positively correlated with achene mass for 2‐week‐old seedlings grown without added nutrients. This correlation was significant but weak with added nutrients at 2 weeks, and by 4 weeks it was no longer significant. Seedling RGR was strongly negatively correlated with achene mass.5. Achene mass variation was related to both seedling fitness and dispersal ability, but compensation was evident mainly as faster RGR in populations with small achenes.

Achene heteromorphism in the cleistogamous species Centaurea melitensis

Centaurea melitensis is a cleistogamous annual plant displaying achene heteromorphism. Variation is linked to capitulum type: a) initial cleistogamous capitula produce thick achenes bearing a short pappus; b) in final cleistogamous capitula achenes are small with a short pappus; and c) chasmogamous capitula produce small achenes with a longer pappus. The present study, carried out in Córdoba (Spain), examines variability in achenes by analysis of morphology, timing, dispersal and germinative capacity, and monitors the subsequent development of seedlings at different densities. Results confirm the heterogeneous nature of the achenes produced, and suggest that Centaurea melitensis has developed a life history strategy (cleistogamy and achene heteromorphism) highly adapted to the unstable habitat (subnitrophilous pioneer pasture communities) in which it grows.

Impact of insects and fungi on doublegee (Emex australis) in the Western Australian wheatbelt

Biotic influences on doublegee(Emex australis Steinheil) seed production wereinvestigated as a precursor to the introduction of new insect biologicalcontrol agents for this weed, and to investigate the cause of doublegeedecline in the northern and central wheatbelt of Western Australia since 1990.The symptoms of the decline are doublegee plants of reduced size withdistorted leaves, collapsed stems, and smaller achenes(the spiny seed-bearing fruit) that crumble when mature.Three sites were investigated in 1992 by surveys for insects and fungi, andinsect and fungus exclusion experiments.Emex stem blight (Phomopsis emicis R. G. Shivas) waspresent at the 3 study sites. The Watheroo site had comparatively high levelsof dock aphids (Brachycaudus rumexicolens Patch) ondoublegee plants, the Badgingarra site had a comparatively high density ofdock sawfly (Lophyrotoma analis Costa) on doublegee, andvery few insects were present on doublegee at the Wongan Hills site. Viruseswere not detected in samples of plants showing the effects of decline.The exclusion experiment showed a significant effect of removing insects andfungi on achene dry weight at the Watheroo site. There was no treatment effectat the Badgingarra and Wongan Hills sites. The biology of the fungus and theaphid lead to the conclusion that the primary cause of doublegee decline isthe dock aphid. This indicates that biological control againstE. australis might be achieved by using insects thatindirectly affect seed quality.

A new Bulbostylis (Cyperaceae) from Somalia

Bulbostylis somaliensis Lye (Cyperaceae) is described from Somalia. It is closely related to B. hispidula (Vahl) R. Haines, but differs in its smaller achenes as well as in the shape and surface structure of the achenes. The major diagnostic characters are the non-triangular achene and the outermost cells to the pericarp, which have several papillae in each cell. Three subspecies are distinguished, viz. subsp. somaliensis, subsp. confusa Lye and subsp. microcarpa (Chiov.) Lye.

Ray Achene Polymorphism and Germination in Ragweed Parthenium (Parthenium hysterophorus)

Ragweed parthenium (Parthenium hysterophorusL. #3PTNHY) growing at six localities between 28°46′N and 13°O'N latitudes in India produced polymorphic ray achenes that varied in size and weight. Frequency of small achenes (1.9 to 2.2 mm) was higher at lower latitude (13°O'N) and that of large achenes (2.5 to 2.8 mm) at higher latitude (28°46′N). Achene weight was positively correlated with its germination percentage. Large-heavy achenes showed better germination than small-light ones.

Morphological and Electrophoretic Divergence between Layia discoidea and L. glandulosa

Layia discoidea (Asteraceae), a narrow serpentine endemic in California, and L. glan- dulosa, a widespread species in the far western U.S.A., originally studied by Clausen et al. (1947), differ strikingly in a number of discrete and quantitative traits yet are fully interfertile, making them an attractive model in which to examine differences sometimes characteristic of plant genera. Layia discoidea differs from L. glandulosa in lacking ray florets and phyllaries and in the structure of its pappus. We have initiated a study of development, character correlation, and genetic divergence between the two species. Layia discoidea had smaller and fewer rosette leaves, was quicker to flower, shorter in stature with fewer stem nodes and shorter internodes, had smaller heads containing many fewer and smaller disk florets, and produced smaller achenes than L. glandulosa. Canonical variates analyses showed that shoot height and number of disk florets were the most important quantitative characters contributing to the species differences in the vegetative and floral analyses, respectively. Electrophoretic analyses of enzymes coded by 21 gene loci demonstrated that popu- lations of the two species have a high genetic identity (I = 0.90). This result suggests that L. discoidea is a recent derivative of L. glandulosa and not, as the Clausen group concluded, a relict species. Both species have duplicated genes specifying the cytosolic isozyme of phosphoglucomutase and tripli- cated genes specifying cytosolic isocitrate dehydrogenase.

Comparison of Achene Characteristics and Combining Ability of Branching and Non‐Branching Near‐Isogenic Sunflower Restorer Lines1

The achene characteristics and combining ability of branching and non‐branching near‐isogenic restorer lines were compared. Branching lines were considerably higher in oil content but had smaller achenes than the non‐branching forms. There was no difference in achene yield, oil content, and achene size between hybrids using branching and non‐branching restorer lines as male parents.

Influence of size of achenes sown and depth of sowing on growth and yield of dryland oilseed sunflowers (Helianthus annuus) on the Darling Downs

Large achenes of sunflower (Helianthus annuus) exhibited a slightly higher germination percentage and greater mean hypocotyl length than small achenes, resulting in a higher field emergence percentage at sowing depths exceeding 6 cm. Size of achenes sown had no effect on achene yield, provided plant populations from large and small achenes were equal. Plants grown from small achenes produced achenes of higher kernel percentage in both seasons, resulting in higher protein percentage in one season and higher oil percentage in the other. Performance of ungraded achenes was equal to that of graded achenes of the same mean size. Deep sowing reduced emergence percentage considerably, especially when small achenes were sown, but the effect of deep sowing on growth and yield was confounded with effects of reduced plant density (because of reduced emergence) and effects of delayed emergence causing slightly later timing of growth and development processes in relation to environmental factors.

The Relationship of Lygus Bugs and Thrips to Fruit Deformity in Strawberries

Lygus bugs, Lygus hesperus Knight, caged on the flowers and fruit of strawberries were found to cause fruit deformity or “Catfacing.” Deformity is caused by bugs feeding on individual achenes rather than by a toxic action on the reccptacle itself. Lygus bugs feed on large and small achenes. Consequently, when fruit deformity is caused by lygus bugs, at least some of the achenes in the depressed areas are enlarged. Poor pollination likewise causes “catfacing,” but in such instances all of the achenes in the depressed areas are small. Thrips, Frankliniella occidentalis (Pergande), do not seem to cause fruit deformity. Their feeding sometimes causes a withering of the smaller flowers, but such blossoms usually do not produce marketable fruit. Moderate populations of thrips cause a limited amount of discoloration of the berries, particularly to the seeds, and the fruit under the calyx, but such damage does not seem to warrant control measures. However, very high populations may feed over the entire surface of developing berries and cause a golden brown discoloration that makes the fruit unmarketable.

HYBRIDIZATION IN THE ANNUAL SUNFLOWERS: HELIANTHUS ANNUUS x H. DEBILIS VAR. CUCUMERIFOLIUS

In 1945 seeds of sunflowers from three localities in Texas were sent to the writer by E. Mortensen. When plants from these seeds were grown they were found to approach H. debilis var. cucumerifolius in many characters although on the whole they were nearer to H. annuus in appearance (fig. 1 ). Subsequently a large amount of herbarium material was studied and it was concluded that natural hybridization between these two species probably occurs in eastern Texas. Field work in Texas in 1949 verified this conclusion, and some observations on the variation of these two species with an analysis of both natural and artificial hybrids is presented in the following paper. Helianthus annuus is a wide-spread weed in much of North America and is morphologically quite diverse. Preliminary remarks concerning its variability have already appeared (Heiser, 1949). Plants of H. annus from eastern Texas are usually very distinctive. The lemon yellow rays, the deep irregular serration (fig. 3, e) and somewhat undulate margin of the leaf, the purple mottled stems, and a tendency to produce long lateral branches from the base of the plant rather effectively distinguish most eastern Texas populations of this species from populations of H. annuus occurring elsewhere, although these traits occasionally appear outside of eastern Texas. In addition, the eastern Texas plants of H. annuus generally have few rays, small disks and bracts, and small achenes. These three