Mature Achenes Research Articles

Two New Species of Scleria Section Scleria (Cyperaceae) from the Neotropics

Two new species are described: Scleria skutchii M. T. Strong & J. R. Grant, a scrambling, vinelike, branching, high-climbing sedge with sharp, spinulose leaf margins, pendulous inflorescences of purple spikelets, a long-stipitate hypogynium, and achenes with a curved apex, from Costa Rica and northwestern Colombia, related to S. macbrideana Gross; and Scleria triquetra M. T. Strong, an erect to ascending sedge that has trigonous achenes bearing tubercles with tufts of trichomes on the angles, from northeastern South America, related to S. huberi C. B. Clarke. A key to the scandent species of Scleria sect. Scleria in Central America and northwestern Colombia is provided, and an illustration, SEM photograph of the mature achene, and comparison to similar taxa are given for each species. Earl Core's (1936) monumental treatment of the American species of Scleria Bergius and his (1965) treatment of the Guayana Highlands species laid a solid foundation for further study of species occurring in the Neotropics. Examination of specimens has led to the discovery of two new species in Scleria sect. Scleria. The genus is typified by Scleria fiagellum-nigrorum Bergius. Section Euscleria of Core (1936), the nominate section of the genus which contains S. flagellum-nigrorum, is not permitted by the International Code ofBotanical Nomenclature, Article 21.3 (Greuter et al., 1988). Species of Scleria sect. Scleria are distinguished from other species in the genus by having a 3-lobed hypogynium with entire lobes. Scleria skutchii M. T. Strong & J. R. Grant, sp. nov. TYPE: Costa Rica. Puntarenas: Canton Golfito, Refugio Nacional de Fauna Silvestre Golfito, Golfito, along road (7 km long) from the soccer field to the microwave transmitter tower, 8?38'N, 83?1 1'W, 25 Dec. 1992, Grant & Rundell 92-02087 (holotype, US sheet #3242501; isotypes, BM, CLEMS, CR, F, GH, K, MARY, MO, NY, P, VDB). Figures 1, 3B. NOVON 4: 296-302. 1994. Species haec a Scleria macbrideana Gross differt foliorum pagina abaxiali pilosa; inflorescentiis (2-)5-10 paniculatis, pendulis, flexuosis; prophyllis basi longo-ciliatis in ramis lateralibus; spicularum pedicellis ad 1 cm longis; acheniis ovatis, apice anguste rotundo et leviter curvirostrato, pilis brevibus dispersis vel in lineis indistinctis. Coarse perennial, with thick, nodose rhizome; vinelike, climbing or scrambling high over vegetation; roots coarse, thick. Culms trigonous, elongate, branching from upper nodes, to 10 m long, 3-5 mm wide, to 10 mm wide near base, scabrous to spinulose on angles, finely ribbed above, coarsely ribbed and channeled near base, glabrous to sparsely pilose. Leaves many; blades green, to 6 dm long, 4-14 mm wide, apex long-acuminate, abaxial side pilose, adaxial side glabrous except at base, a few hairs sometimes along the midvein, harshly spinulose along margins and midvein beneath, the barbs up to 0.5 mm long; sheaths green, closely overlapping in young foliage, finely veined, pilose to glabrescent at maturity, scabrous to spinulose on the angles, the convex contraligule firm, pubescent to glabrescent at recurved apex with hairs to 1 mm long. Inflorescence of (2-)5-10 axillary panicles from the upper sheaths; panicles borne on long, slender peduncles becoming pendulous at maturity; panicle branches smooth, or scabrous only near base, ascending, elongate, minutely scabrous on angles; bractlets linear-lanceolate to setaceous, scabrous, long-ciliate on margins at expanded base. Spikelets unisexual; pistillate spikelets elliptic to elliptic-obovate, 5-7 mm long, 3 mm wide, on slender, trigonous to subcompressed pedicels up to 1 cm long; staminate spikelets oblong-ovate, 3-4 mm long, 12 mm wide, usually on shorter pedicels than the pistillate, but sometimes up to 1 cm long. Pistillate scales 6-9 (including the reduced fertile scale); lower sterile scales ovate, 2-2.5 mm long, 1.5-2.0 mm wide; upper sterile scales widely ovate, 3.0-3.5 mm long, 3.5-4.5 mm wide, green with purple margins, at maturity becoming darker, usually tinged with purple, glabrous, ciliate along margins near base, the apex short-mucronate, scabrous, recurved at This content downloaded from 207.46.13.113 on Wed, 05 Oct 2016 04:06:01 UTC All use subject to http://about.jstor.org/terms Volume 4, Number 3 1994 Strong Scleria Section Scleria

Carpels as leaves: meeting the carbon cost of reproduction in an alpine buttercup.

We investigated the role of photosynthesis by reproductive organs in meeting the carbon costs of sexual reproduction in the snow-buttercup, Ranunculus adoneus. The exposed green carpels of snow-buttercup flowers have 1-2 stomata each. Net carbon assimilation rates of flowers are negative during bud expansion, but rise to zero at maturity, and become positive during early fruit growth. Experimental removal of separate whorls of flower parts demonstrated that the showy, nectary-housing petals account for most of the respiration cost of flower presentation. Conversely, photosynthesis by female organs contributes to a flower's carbon balance. Dipteran pollinators of R. adoneus are most active in sunny mid-morning to mid-afternoon intervals. At this time of day, rates of carpel photosynthesis (Amax) meet respiratory costs of pollinator attraction in fully expanded flowers. Achenes remain photosynthetically active until dispersal, and positive net carbon assimilation rates characterize infructescences throughout fruit maturation. Photosynthetic rates of achenes are positively correlated with infructescence growth rates. We tested the causal basis of this relationship by experimentally shading developing infructescences. Mature achenes from shaded infructescences were 16-18% smaller than those from unshaded controls. Leaf photosynthetic rates did not differ between plants bearing shaded and unshaded seed heads. Since female reproductive organs are only 8% more costly in terms of caloric investment than male ones and contribute to their own carbon balance, it is plausible that the energy cost of male function equals or exceeds that of female function in this hermaphroditic species.

Oviposition and Larval Bionomics of Two Weevils (Coleoptera: Curculionidae) on Sunflower

Use of cultivated sunflower (Helianthus annum L.) as a host by two species of seed weevils, Smicronyx fulvus LeConte, the red sunflower seed weevil, and S. sordidus LeConte, the gray sunflower seed weevil, was compared using dissection of achenes from naturally and artificially infested plants. The gray seed weevil oviposits on the tips of unopened sunflower florets before anthesis. Larvae migrate through the corolla tube, penetrate the developing achene, and begin extensive feeding at the achene base. Achenes infested by the gray sunflower seed weevil are enlarged, lack an embryo, and appear to be a type of gall. The red sunflower seed weevil oviposits internally in more mature achenes after anthesis has begun, and these achenes have well-developed seed embryos.

Plant Regeneration from Excised Cotyledons of Mature Strawberry Achenes

A protocol was developed for excising and culturing cotyledon explants from mature achenes of strawberry (Fragaria × ananassa Duch.). Cotyledon explants formed callus with multiple shoot buds on agar-solidified Murashige and Skoog media containing several combinations of hormones (1 μm 2,4-D; 10 μm 2,4-D; 1 μm BA + 1 μm 2,4-D; 1 μm BA + 10 μm 2,4-D; 5 μm BA; 5 μm BA + 1 μm 2,4-D; 5 μm BA + 10 μ m 2,4-D; 5 μ m BA + 5 μm NAA; 5 μ m BA + 15 μ m NAA). After three subcultures, only tissues maintained on the medium containing 5 μm BA + 5 μm NAA continued to form shoots. Tissues transferred to other media eventually died (1 μm 2,4-D; 1 μ m BA + 10 μ m 2,4-D; 5 μ m BA; 5 μ m BA + 1 μ m 2,4-D), became unorganized (1 μm BA + 1 μm 2,4-D; 5 μm BA + 10 μm 2,4-D; 5 μm BA + 15 μm NAA), or formed roots (10 μm 2,4-D). Whole plantlets were produced by transferring callus with buds to medium lacking hormones. The rapid regeneration of clonal plantlets from cotyledon explants may be useful for reducing variability in future developmental studies. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (BA); (2,4-dichlorophenoxy) acetic acid (2,4-D); and 1-naphthaleneacetic acid (NAA).

Étude de la plasticité phénotypique chez le Chrysanthemum leucanthemum. I. Croissance, allocation de la biomasse et reproduction

Phenotypic plasticity was experimentally studied in plants sampled from two tetraploid populations of ox-eye daisy, Chrysanthemum leucanthemum L. Plants were cloned and ramets were grown in an outdoor garden, in two independent experiments aimed at measuring the effects of light intensity (three treatments) and nutrient level (three treatments). When plants of the same genotype were grown under different light intensities, phenotypic plasticity was high for the following characteristics: total biomass, root weight to total weight ratio, leaf area, leaf area to total weight or specific leaf weight ratio, stem height, branching, number of heads, and time of flowering and fruiting. Genotypes grown under the three nutrient levels showed less plasticity, especially for leaf-related features. Biomass allocation patterns were also measured. Generally, lower light intensities resulted in an increase of allocation to leaves and a corresponding decrease of allocation to roots. On the other hand, lower nutrient levels caused an increase of allocation to roots accompanied by a decrease of allocation to heads, but had little effects on allocation to leaf material. The effective reproductive effort (percentage of biomass allocated to mature achenes) was higher under the lowest light intensity level, but did not change significantly with nutrient levels. The results are discussed in relation to the specificity of plastic responses with respect to the nature of environmental stresses. The prolific production of heads that remained immature at the onset of cold autumn temperatures is interpreted as a nonadaptative tactic in C. leucanthemum.

Taxonomy and Distribution of Chaptalia dentata and C. albicans (Asteraceae: Mutisieae)

Chaptalia dentata (L.) Cass. andC. albicans (Sw.) Vent. ex Steudel incorrectly have been recognized as conspecific in recent treatments. Although they are vegetatively similar, they differ in features of the flowers and fruits—especially the mature achenes. Both species occur in the Bahamas and the Greater Antilles of the West Indies:Chaptalia dentata is endemic to that area, absent only from Jamaica;C. albicans is more widespread, as it occurs in Jamaica as well as in scattered localities on the American mainland—southern Florida, various localities in Belize, Honduras, and Guatemala, and the Mexican states of Veracruz, San Luis Potosi, Chiapas, and Yucatan.

Germination and Dry-Matter Accumulation in Dimorphic Achenes of Tansy Ragwort (Senecio jacobaea)

Mature achenes from tansy ragwort (Senecio jacobaea L. ♯3 SENJA) capitula borne on lower branches had greater average dry weights and higher percentage germination than those closer to the apex, but these higher averages were obtained because more achenes in these samples were filled. Physiological maturity was attained in ray achenes 21 days past flowering (DPF), 24 DPF in peripheral disk achenes, and 27 DPF in central disk achenes. Maximum germination occurred at 18 DPF in ray and peripheral disk achenes and at 21 DPF in central disk achenes. Neither achene type was shown to have innate dormancy. Disk and ray achenes germinated most rapidly at alternating temperatures of 30/20 C.

Germination, establishment, and spread ofSoliva valdiviana(Compositae)

Abstract Achene production in So/iva occurs from mid November until the end of January but germination in the field is usually delayed until the first heavy rain in autumn. Two species of Soliva, S. valdiviana and S. pterosperma, occupy very similar ecological niches. Both species have a prostrate growth form which enables them to compete successfully with perennial lawn grasses in close-cut turf. Laboratory studies showed that whereas achenes produced early in the season take a long time to germinate, those produced later germinate rapidly. This feature is particularly marked in S. valdiviana. Germination is also greatly stimulated by light. About 40 days elapse from the first readily observable signs of capitulum formation to mature achene production in S. valdiviana. A central capitulum is produced first and under favourable circumstances capitula will subsequently develop on the laterals. Achenes will mature on detached capitula if given sufficient moisture and light. Presumably summer conditions in A...

THE GENECOLOGY OF LAWN WEEDS VI. THE ADAPTIVE SIGNIFICANCE OF VARIATION IN ACHILLEA MILLEFOLIUM L. AS INVESTIGATED BY TRANSPLANT EXPERIMENTS

SUMMARYThe performance of 21 populations of Achillea millefolium L., originating from I lawns, II grazed sites, III grasslands seasonally reduced in height by cutting and/or grazing and IV grassy areas not seasonally reduced in height by cutting and/or grazing, was investigated by transplanting clone‐propagated material into a mature lawn. The response of a small number of contrasting populations was also studied in mown and tall grass plots of a reciprocal transplant experiment.There was no evidence, from the mown treatment of either experiment, to support the hypothesis that A. millefolium populations originating from certain lawns or grazed sites, and notably dwarf in standard cultivation, were more successful than others in vegetative spread, dry wt yield or reproduction. In both experiments plants originating from lawns were not uniformly successful. Also, individuals from all four habitat groups proved to be vegetatively vigorous in mown plots. Six plants (three from lawns, two from pasture and one from waste ground) fruited successfully in the mown plots of the reciprocal transplant experiment.Experiments with tall grass plots did not support the notion of tall grass races of A. millefolium. Such plots revealed considerable variability in all populations and plants from several habitat groups produced mature achenes in tall grass plots.Fruiting of A. millefolium is very rare in well‐kept lawns and the apparent clones in such habitats are likely to be the result of achene dispersal from habitats where the intensity and/or periodicity of grazing and/or mowing is insufficient to prevent fruiting.

Establishment of Rhinocyllus conicus (Col.: Curculionidae) on Italian Thistle in Southern California

Adults of Rhinocyllus conicus Froelich collected in southeastern Italy were released in See Canyon, California, for the biological control of Italian thistle, Carduus pycnocephalus L. Field data on the incidence and increase of this weevil at this colonization site are presented. Larvae destroyed ca. 90% of an avg 7.3 mature achenes in 300 infested flowerheads sampled in 1976. An avg of 1.8 (range 1–6) weevils was reared from each flowerhead. By 1977, 91% of 561 capitula examined in a 2 man-h search bore at least one and an avg of 3.4 (max 11) eggs; however, no population reduction of Italian thistle as yet was evident. Biotic mortality factors reported for R. conicus include a low incidence of larval parasitism by an unidentified species of Habrocytus (Hym.: Pteromalidae) and occasional predation of adults by the crab spider, Xysticus californicus Keyserling (Araneida: Thomisidae). During 1976 and 1977, totals of 1800 and 6500 weevils from this established field colony were transferred to 4 and 13 new locations in southern California, respectively.

THE DEVELOPMENT OF THE ACHENE OF POLYGONUM PENSYLVANICUM: EMBRYO, ENDOSPERM, AND PERICARP

A study was made of the ontogeny of the achene of Polygonum pensylvanicum L. from fertilization to maturity. The proembryo is classified as the Polygonum Variation, Asterad Type. Cotyledons are initiated three days after anthesis, and by the fifth day procambium is present in the embryo axis. At approximately seven days after anthesis, the embryo begins to curve and occupy a marginal position in the ovary. By ten days the first foliage leaf primordium is initiated at the stem apex of the embryo. At maturity the embryo consists of two cotyledons, a plumule composed of the stem apex and one leaf primordium, and a hypocotyl with a well‐developed radicle. Endosperm nuclei begin to divide before the first division of the zygote. Cell wall formation begins in the endosperm at the micropylar end of the embryo sac and proceeds toward the chalazal region. By the fifth day the endosperm is completely cellular, except for a basal projection; and a peripheral meristem has been established. At approximately ten days the peripheral meristem ceases periclinal cell division and becomes the aleurone. At the time of fertilization the ovary wall has its full complement of cell layers. The walls of the outermost cells elongate and become convoluted. Subsequent thickening and lignification of these cell walls produce the hard epicarp of the mature achene.

Anatomy and Systematic Position of Centaurodendron and Yunquea (Compositae)

The genera Centattrodendron and Yunquea are remarkable in that they are both "rosette trees" which have been interpreted as belonging to the tribe Cynareae (Skottsberg 1938) and are endemic to the island Masatierra in the Juan Fernandez Islands. Centaurodendron consists of two species, C. dracaenoides Johow and C. palmiforme Skottsberg, whereas Yunquea tenzii Skottsberg is the single species of its genus. The main purpose of the present study is to show how anatomical evidence bears on the systematic relationships which have been proposed on the basis of gross morphology. Because Centaurodendron and Yunquea are the only arboreseent genera referred to Cynareae, and because they show little superficial similarity to other Cynareae in vegetative characters, a study of their anatomy is desirable in determining if this is, indeed, the correct disposition of these genera. A secondary problem is created by the genus Yutnquea, which Skottsberg (1929) erected on the basis of scanty vegetative material. Although subsequent collections have furnished no flowers of this plant, which evidently flowers with extreme infrequency, anatomical data from the vegetative portions of the plant and from recently collected mature achenes appear to be decisive in assessing Skottsberg's (1929) suggestion that it should be regarded as a genus closely related to Centaurodendron. Individuals of Yunquea are rare, and the localities in which they grow are difficult of access (Kunkel 1957; Skottsberg 1953). It iray become extinct, as has so much of the autochthonous Juan Fernandez vegetation,without having been collected in the flowering state. The recent discovery (Skottsberg 1957) of Centaurodendron paalmiforme is significant, for this species shows greater similarity to Yunquea than does C. dracaenoides. Moreover, anatomical characters can be used in contrasting the two species of Centaurodendron.

A REVISION OF THE GENERA « ASPILIA », « BLAINVILLEA » AND « WEDELIA » IN WEST AFRICA

SUMMARY A discussion of the taxonomy and nomenclature of the West African representatives of the genera Aspilia, Blainvillea and Wedelia (COMPOSITAE— Helianthoideae), while drawing attention to misconceptions which have confused the proper understanding of the constituent taxa in the past, leads to a re-assessment of the value of certain morphological features and results in the following conclusions:— 1. The genus Wedelia is not indigenous in West Africa being represented only by the introduced Wedelia trilobata (L.) Hitchc. 2. The genus Blainvillea is represented by the single indigenous species Blainvillea gayana Cass. 3. The critical distinction between Aspilia and the other two genera rests in the fertility of the ray florets, i. e. the capacity of these florets to develop mature achenes rather than the mere presence of styles and stigmas. The existence of species of Aspilia which possess « functionless » styles and stigmas is of interest in relation to the evolution of sterility in that genus. In on...