Common Milkweed Asclepias Syriaca Research Articles

Seasonal and diurnal gas exchange differences in ozone-sensitive common milkweed ( Asclepias syriaca L.) in relation to ozone uptake

Stomatal conductance and net photosynthesis of common milkweed ( Asclepias syriaca L.) plants in two different soil moisture regimes were directly quantified and subsequently modeled over an entire growing season. Direct measurements captured the dynamic response of stomatal conductance to changing environmental conditions throughout the day, as well as declining gas exchange and carbon assimilation throughout the growth period beyond an early summer maximum. This phenomenon was observed in plants grown both with and without supplemental soil moisture, the latter of which should theoretically mitigate against harmful physiological effects caused by exposure to ozone. Seasonally declining rates of stomatal conductance were found to be substantial and incorporated into models, making them less susceptible to the overestimations of effective exposure that are an inherent source of error in ozone exposure indices. The species-specific evidence presented here supports the integration of dynamic physiological processes into flux-based modeling approaches for the prediction of ozone injury in vegetation.

Monarch Butterfly Oviposition on Swallow-Worts (<I>Vincetoxicum</I> spp.)

As black swallow-wort, Vincetoxicum nigrum L. Moench, and pale swallow-wort, V. rossicum (Kleopow) Barbar., spread throughout the northeastern United States and southern Canada, there is concern about the impact of these invasive plants on populations of the native North American monarch butterfly Danaus plexippus L. Recent laboratory studies in New York and Ontario, Canada, have found little or no oviposition by monarch butterflies on the two Vincetoxicum species. In Rhode Island, we found 10.5-21.7% oviposition on Vincetoxicum species relative to common milkweed Asclepias syriaca L. in choice tests and 11.9-20.3% in no-choice tests in 2 yr of laboratory testing. These results were supported by field cage trials where monarchs given a choice between V. nigrum and A. syriaca laid 24.5% of their eggs on V. nigrum. In surveys of three pasture fields in Rhode Island where relative coverage of A. syriaca exceeded that of V. nigrum by a 0.77:0.23 ratio, 15.4% of monarch eggs were found on V. nigrum plants. In V. nigrum stands with very little A. syriaca (6.25 stems/ha), monarch egg density on V. nigrum was found to be over five times greater than in the three mixed pasture fields. In none of our laboratory or field evaluations was there any survival of monarch larvae on Vincetoxicum species. It seems that in Rhode Island, Vincetoxicum species serve as an oviposition sink for monarch butterflies. These findings suggest that East Coast butterflies may differ in host selection from those in central New York and southern Ontario, Canada.

A 13-Week Comparison of Passive and Continuous Ozone Monitors at Forested Sites in North-Central Pennsylvania

ABSTRACT Ogawa passive O3 samplers were used in a 13-week study (June 1-September 1, 1999) involving 11 forested and mountaintop sites in north-central Pennsylvania. Four of the sites were collocated with TECO model 49 O3 analyzers. A significant correlation (p < 0.0001) was found for 24-hr average weekly O3 concentrations between the two methodologies at the four sites with collocated monitors. As expected, there were positive relationships between increasing elevation of the sites and increasing O3 concentrations. No O3 exposure patterns were found on a west-to-east or south-to-north basis; however, the area known for lower O3 exposures within a smaller subsection of the study area showed consistently lower O3 exposures. Preliminary results regarding relationships of symptom responses within O3-sensitive bioindicators are also presented with black cherry (Prunus serotina, Elirli.) and common milkweed (Asclepias syriaca, L.) showing clear evidence of increasing injury with increasing O3 exposures. Due to the extremely dry conditions encountered in north-central Pennsylvania during the 1999 growing season, O3-induced symptoms were sporadic and quite delayed until late-season rains during the latter portion of the observation period.

THE ROLE OF EXPERIENCE IN DETERMINING PATCH-USE BY ADULT CRAB SPIDERS

Summary I tested the role of the previous substrate in hunting-patch choice using a sit-and-wait predator, the crab spider Misumena vatia. Adult females that hunted on flowers of common milkweed Asclepias syriaca and pasture rose Rosa carolina differed in their subsequent choices of these substrates as a consequence of both the species of flower encountered and their recent experience with these flowers. In six-hour tests, individuals taken from both milkweed and rose flowers and later returned to the same species of flower remained and hunted on these sites in similar frequencies. However, spiders from milkweed placed on rose remained significantly less frequently than spiders from rose placed on milkweed or spiders returned to their accustomed flower species. A higher proportion of individuals that left their sites did so more quickly from accustomed than from unfamiliar flower species. Capture of prey increased the probability that a spider would remain during the test period, but even spiders not capturing prey showed the trends noted above. These results demonstrate that immediately previous experiences can modify patch-choice behavior in ways that significantly affect the foraging success of an individual, with important consequences for lifetime fitness.

Variations interpopulations de la longueur des aigrettes et des caractéristiques des follicules de l'asclépiade commune

A study was carried out in 1987 on five populations of common milkweed (Asclepias syriaca L.) from the Montréal region, Québec, Canada, to determine if differences between pappus length, and length and weight of follicles existed and could be due to early or late flower pollination and to populations. Pollination date had no effect at harvest on pappus length and follicle length and weight. Significant differences of pappus length, follicle length and weight were found. Key words:Asclepias syriaca, intraspecific variation, follicle, pappus

Milkweed as a New Cultivated Row Crop

Fifty milkweed ecotypes collected from 10 states, including showy milkweed (Asclepias speciosa Torr.), common milkweed (Asclepias syriaca L.), and Kansas-derived hybrids of these two sympatric species were field tested as a new row crop. Interest initiated from the recent use of the harvested floss, produced as tufts of hollow cellulose seed hairs within fruiting follicles (pods), as an insulative batting fiber to supplement or replace the use of costly ($25/Ib) imported white goose down. Variation in floss productivity between different ecotypes was anlyzed over 4 yr (...)

MATERNAL AND PATERNAL EFFECTS ON FOLLICLE PRODUCTION IN THE MILKWEED ASCLEPIAS SYRIACA (ASCLEPIADACEAE)

We measured follicle production from a diallel cross among ten clones of the common milkweed Asclepias syriaca, to assess the relative contributions of maternal and paternal parents. Specific parental combinations differed in the ability to set fruit, indicated by a significant nuclear specific effect accounting for 28% of the observed variance in follicle production. Several mechanisms might contribute to this effect, including shared incompatibility alleles and expression of zygotic genotypes. The nuclear general effect was not significant, however, suggesting a lack of additive genetic variation for offspring control of fruit maturation. Maternal effects also had an important effect on follicle production, as demonstrated by a significant reciprocal general effect (26% of the variance), almost entirely due to a large maternal component. The small reciprocal general variance component attributable to paternal effects, and nonsignificant reciprocal specific effect, indicating little maternal parent‐zygote interaction, suggest that female choice through selective follicle maturation was not important in this experiment. The clones varied in proportion of reproductive output through female function, but a significant tradeoff between male and female success was not detected.

Pollinium Germination and Putative Ovule Penetration in Self- and Cross-pollinated Common Milkweed Asclepias syriaca

-We compared success and speed of pollinium germination and putative ovule penetration in selfand cross-pollinated flowers from three clones of common milkweed (Asclepias syriaca). Even though common milkweed is largely or entirely self-incompatible, success of selfed flowers equalled or exceeded that of crossed ones (87% vs. 74% germination, 78% vs. 63% putative penetration). This result is consistent with the postfertilization incompatibility mechanism proposed for A. syriaca. Clones differed in success, and the recipient clone with the highest combined selfed and crossed success (97% vs. 74% germination for the others, 95% vs. 56% putative penetration for the others) also developed most rapidly (90% vs. 45% germination for the others 1 day after pollination; 90% vs. 13% putative penetration after 1 day). The significant among-clone variation suggests that factors intrinsic to the clones strongly affect rates of fertilization and putative penetration.

The Quality of Pollination by Diurnal and Nocturnal Insects Visiting Common Milkweed, Asclepias syriaca

-We studied the contributions of diurnal and nocturnal insects to pollination of common milkweed Asclepias syriaca L. (Asclepiadaceae) in Maine. Diurnal insects (mainly bumblebees, Bombus spp.) visited five times as many flowers and removed 10 times as many pollinaria as nocturnal visitors (mainly moths). Stalks exposed to diurnal insects produced 2.5 times as many pods as did those exposed to nocturnal insects. However, hand pollination of flowers at midday and at midnight resulted in similar pod production. Seeds per pod, seed mass, germination time and seedling quality did not differ between diurnal and nocturnal treatments. We conclude that nocturnal visitors performed pollination of higher quality in terms of pods produced per pollinator visit, because a visit from a nocturnal insect was twice as likely to result in the production of a pod than a diurnal visit. However, diurnal flower visitors were more important pollinators as a consequence of the large number of individuals participating.

Stochastic prey arrivals and crab spider giving-up times: simulations of spider performance using two simple "rules of thumb".

We compared the patch-choice performances of an ambush predator, the crab spider Misumena vatia (Thomisidae) hunting on common milkweed Asclepias syriaca (Asclepiadaceae) umbles, with two stochastic rule-of-thumb simulation models: one that employed a threshold giving-up time and one that assumed a fixed probability of moving. Adult female Misumena were placed on milkweed plants with three umbels, each with markedly different numbers of flower-seeking prey. Using a variety of visitation regimes derived from observed visitation patterns of insect prey, we found that decreases in among-umbel variance in visitation rates or increases in overall mean visitation rates reduced the "clarity of the optimum" (the difference in the yield obtained as foraging behavior changes), both locally and globally. Yield profiles from both models were extremely flat or jagged over a wide range of prey visitation regimes; thus, differences between optimal and "next-best" strategies differed only modestly over large parts of the "foraging landscape". Although optimal yields from fixed probability simulations were one-third to one-half those obtained from threshold simulations, spiders appear to depart umbels in accordance with the fixed probability rule.

Roles of Pollen and Ovary Age in Follicle Production of the Common Milkweed Asclepias syriaca

Roles of Pollen and Ovary Age in Follicle Production of the Common Milkweed Asclepias syriaca

ROLES OF POLLEN AND OVARY AGE IN FOLLICLE PRODUCTION OF THE COMMON MILKWEED ASCLEPIAS SYRIACA

Using cross‐pollination experiments, pollinia viability of the common milkweed Asclepias syriaca L. (Asclepiadaceae) did not change significantly over the five‐day life of the flowers, but stigma receptivity decreased over threefold over this period. During most of the season pollinators inserted over 90% of their pollinia into flowers during the first two days following anthesis. However, pollinators were scarce during the first few days of flowering, and they inserted over 60% of their pollinia into flowers three or more days old. This behavior potentially decreased outcrossing success and increased the relative male contribution of the flowers. Pollinator visitation patterns may play an important role in determining the functional sexuality of these plants.

VARIATION IN THE POLLINARIA, ANTHERS, AND ALAR FISSURES OF COMMON MILKWEED (ASCLEPIAS SYRIACA L.)

We measured 10 characters of pollinaria, anthers, and alar fissures from the flowers of seven clones of common milkweed Asclepias syriaca L. to test whether significant differences existed among them. Strong among‐clone differences existed for most of these characters. However, these differences were not correlated with each other, except for width of the alar fissure and width of the translator arm. Thus, these floral structures vary mostly in shape, rather than size per se. Few correlations among characters occurred at a within‐clone level. Clones growing in the open and shade differed in half of the characters measured, but habitat did not substantially change the among‐clone size patterns observed. The alar fissure–translator arm relationship might promote differential uptake of pollinia; however, A. syriaca does not exhibit a clear separation into donor and recipient clones.

Seed predation and patterns of fruit production in Asclepias syriaca L.

Seed predation in relation to patterns of pod (and seed) distribution was examined in five samples of the common milkweed (Asclepias syriaca L.), in tests of the "resource-concentration" effect both within- and beween-plants. The proportion of pods in a cluster that were attacked, particularly by the weevil Rhyssomatus lineaticollis, was not consistently related to the number of pods contained in a cluster, the frequency of cluster sizes in a population, or the variance of cluster sizes on a stem. Proportions of pods attacked per stem were not correlated with stem density in one sample and were not associated with stem height in any sample. Large clusters of pods produced more undamaged pods and, by this measure, were more successful than smaller clusters, but there was no tendency in any population for stems to produce the more successful cluster sizes more frequently. Stems producing more clusters of pods also produced more undamaged pods. We found no evidence that weevil predation contributed to the regulation of the distribution of pods among clusters on a stem.

Herbicidal Control of Common Milkweed (Asclepias syriaca)

Five field experiments were conducted to evaluate effectiveness of postemergence herbicidal treatments. Amitrole (3-amino-s-triazole) at 1.1 kg ai/ha and picloram (4-amino-3,5,6-trichloropicolinic acid) at 0.6 kg ai/ha reduced stands of common milkweed (Asclepias syriaca L.) for a 4-yr period. Glyphosate [N-(phosphonomethyl)glycine] at 2.2 kg ai/ha reduced stands of milkweed for two to three growing seasons. Glyphosate or amitrole applied in June (early bud stage) more effectively reduced milkweed stands in the second year than did the herbicides when applied in August (post-flowering stage). Treatments of 2,4-D [(2,4-dichlorophenoxy)acetic acid], 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid], and dicamba (3,6-dichloro-o-anisic acid) did not reduce stands of common milkweed.

Allelochemic Effects of Leaf Extracts of Ambrosia trifida (Compositae)

Aqueous extracts from leaves of giant ragweed reduced growth in sorghum seedlings, and reduced germination in sorghum and radish. Five phenolic compounds from these extracts were isolated and characterized, but not identified. Germination bioassays using these compounds demonstrated that each of the five depressed germination, and the depression related to concentration. It is suggested that the water-soluble allelochemics from giant ragweed contribute to any interference effect this weed may have on growth of associated species. A number of investigations of the distribution of vegetation in natural floristic communities have shown that allelopathy is an im- portant determinant in these plant associations (Rice 1974). Some of the recognized allelopathic plants found in these investigations are common weeds (Hamilton and Bucholtz 1955, Abdul-Wahab 1967, Wilson and Rice 1968, Parenti and Rice 1969, Neill and Rice 1971). However, the allelopathic potential of only a few weedy species of agronomic fields has been investigated. Bell and Koeppe (1972) reported giant foxtail (Setaria faberii Herrm.) caused allelo- pathic interference with the growth of corn. Both curled dock (Rumex crispus L.) and common milkweed (Asclepias syriaca L.) contain water-soluble inhibitors which may contribute to yield reduc- tions in grain sorghum (Einhellig and Rasmussen 1973, Rasmussen and Einhellig 1975). Several allelopathic mechanisms of velvetleaf on soybean and grain sorghum have been demonstrated (Colton 1978). These studies suggest that in arable fields allelopathy must be considered as part of the explanation of weed-induced reductions in plant growth and crop yields. Giant ragweed (Ambrosia trifida L.) is a common invader of waste areas and crop land of much of the United States (Muencher 1936). It germinates in early spring, stimulated by general soil

Population and Maturation Characteristics of the Common Milkweed

Maturation rate, pod production, and density of common milkweed (Asclepias syriaca L.) were determined at sites in east-central Missouri. Emergence of milkweeds in May was followed by blooming of flowers in late June, production of full-size follicles (average of 5.1 per plant) by late July, and release of seed in mid-September. Density was 1 to 3 plants per m2 and spacing of plants in 1.4 m2 samples was equidistant. Significant. positive correlations were found between mean height of milkweeds and pH, magnesium and calcium concentrations in the soil, and between density and pH of the soil.

Growth Characteristics of Common Milkweed

Seed dormancy of common milkweed (Asclepias syriaca L.) is broken by a few days of moist low-temperature after-ripening. The duration of low-temperature after-ripening of the seeds is temperature dependent. Seedling emergence is best when the seeds are planted 1 to 2 cm deep and extremely limited when planted 6 cm deep. Seedlings have the capacity to produce new shoots if clipped in the 1 to 1¾-leaf pair stage and multiple shoots if clipped in the 2 to 2½-leaf pair stage. All seedlings reaching the 4 to 4½-leaf pair stage before clipping produced new shoots.

COMPARISON OF THE LIFE CYCLE OF LEPTOMONAS ONCOPELTI AND PHYTOMONAS ELMASSIANI.

SYNOPSIS. After several years of field work devoted primarily to determining the incidence of infection of the common milkweed Asclepias syriaca with the trypanosomatid Phytomonas elmassiani, the life cycle of this parasite was determined under controlled conditions. Upon ingestion of phytomonads by the bug Oncopeltus fasciatus, reproduction apparently ceases but growth of individual phytomonads continues until they assume relatively giant proportions. Ten days after ingestion, giant forms are found in the hemocoel of the bug and by 12 days similar forms are present in the salivary glands. In this latter organ, unequal fission takes place with the ultimate formation of numerous forms similar to those found in the plant. Within 2 weeks after these infected bugs had fed on milkweeds, parasites were detected in the latex of formerly non‐parasitized plants. The lack of reproduction in the alimentary tract, the formation of giant forms, and the migration through the hemocoel to the salivary glands contrast markedly with the development of Leptomonas oncoptlti in the same bug. In the latter organism, budding leads to the formation of leishmaniform organisms which pass out with feces and are presumably the infective stage of the leptomonad.

Molecular Properties of Milkweed Cellulose

The seed hairs of the common milkweed (Asclepias syriaca, L.) have been found to contain 39.6% alpha-cellulose, 35.3% pentosan (chiefly xylan), and 15.1% lignin. The alpha-cellulose fraction was entirely composed of anhydroglucose, the hemicellulose por tion of anhydroxylose units. The original material, in addition, also contained minor amounts of arabinose and uronic acid residues. Direct nitration of the untreated fibers gave a cellulose nitrate with glucose as the only constituent sugar in a yield corresponding to a content of 29% cellulose in the original material. The average degree of polymerization of the nitrate was 5800, as determined viscometrically with corrections applied for the effects of rate of shear and nitrate substitution on the intrinsic viscosity. Fractional precipitation of the nitrate derivative was carried out with acetone water as the solvent-nonsolvent system. The chain-length distribution had only one peak and exhibited a considerable right-hand skewness. The lower D.P. limit was 2500 and the upper 8000, with the maximum located at a D.P. of 4000.