Electron Beam Irradiation Isolates Cellulose Nanofiber from Korea “Tall Goldenrod” Invasive Alien Plant Pulp

This work investigates the possibility of isolating cellulose nanofibers from pulps of tall goldenrod plant, which are invasive plants in Korea, by a convenient method, without strong acids or high-pressure homogenization, using electron beam irradiation (EBI). The obtained cellulose nanofibers were characterized by scanning electron microscopy (SEM), ultraviolet–visible (UV–vis) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and in terms of their mechanical properties. SEM showed that the initially isolated 10-μm-diameter cellulose fibers became more finely separated with increasing EBI dose, and that cellulose fibers treated with 300 kGy of EBI were separated into long cellulose nanofibers of around 160 nm in diameter. In addition, the paper samples prepared from more finely separated fibers generated by using higher doses of EBI had enhanced UV–vis transmittance. Via the XRD analysis, we observed that cellulose I in the EBI-treated cellulose fibers were gradually converted into a different type of cellulose similar to cellulose type II, as the EBI dose increased. Meanwhile, the TGA demonstrated that the finely separated cellulose fibers observed after administering the high EBI dose had lowered thermal stability due to the reduction of cellulose I but higher char yield. In addition, tensile strengths of paper samples increased with decreasing the diameters of their constituent fibers that result from the different EBI doses used in the preparation of the paper pulp.

Distribution of the Specialist Aphid Uroleucon nigrotuberculatum (Homoptera: Aphididae) in Response to Host Plant Semiochemical Induction by the Gall Fly Eurosta solidaginis (Diptera: Tephritidae)

Many plants use terpenoids and other volatile compounds as semiochemicals. Reception of plant volatiles by conspecifics may trigger a defensive phytochemical response. These same compounds can also function as host recognition signals for phytophagous insects. In this experiment, we find that when the specialist gall-forming fly Eurosta solidaginis (Fitch; Diptera: Tephritidae) attacks its tall goldenrod (Solidago altissima (L.; Asterales: Asteraceae)) host plant, the fly indirectly induces a phytochemical response in nearby tall goldenrod plants. This phytochemical response may, in turn, act as a positive signal attracting the goldenrod specialist aphid Uroleucon nigrotuberculatum (Olive; Hemiptera: Aphididae). Laboratory-based experiments exposing ungalled tall goldenrod plants to the volatiles released by E. solidaginis galls demonstrated a consistent increase in foliar terpenoid concentrations in ungalled plants. Analysis of tall goldenrod stem and gall tissue chemistry revealed induction of terpenoids in gall tissue, with a simultaneous decrease in green leaf volatile concentrations. Field experiments demonstrated a consistent spatial relationship in tall goldenrod foliar terpenoid concentrations with distance from an E. solidaginis gall. Both laboratory and field experiments establish consistent induction of the terpene β-farnesene, and that this compound is a strong positive predictor of U. nigrotuberculatum aphid presence on goldenrod plants along with plant biomass and several other foliar terpenoids. These findings suggest E. solidaginis induced phytochemistry, especially β-farnesene, may be acting as a kairomone, driving aphid distribution in the field.

Inhibitory Activities of Momilactones A, B, E, and 7-Ketostigmasterol Isolated from Rice Husk on Paddy and Invasive Weeds

Rice husk has been exploited as a potential source of allelochemicals. In this study, four bioactive compounds including momilactone E (ME), 7-ketostigmasterol (7KS), momilactone A (MA), and momilactone B (MB) were isolated by column chromatography (CC) to yield 2.7, 0.3, 11.7, and 8.3 mg/kg rice husk, respectively. The structures of the isolated compounds were identified and confirmed by spectroscopic techniques consisting of 1H and 13C nuclear magnetic resonance (NMR), electrospray ionization mass (ESI), high-resolution mass spectrometry (HR-MS) and infrared spectroscopy (IS). An advanced quantitative method for MA and MB was achieved to increase the detectable yields of MA and MB in rice husk to 51.96 and 42.33 µg/mL, respectively. The inhibitory activities of MA, MB, ME, and 7KS were examined on lettuce (Lactuca sativa), barnyard grass (Echinochloa crus-galli), and tall goldenrod (Solidago altissima) in bioassays. The allelopathic activities of ME and 7KS were compared with those of potent phytoalexin momilactones A (MA) and B (MB), and the standard p-hydroxybenzoic acid (pHA). Results showed that both MA and MB exhibited stronger inhibitory activity than ME and 7KS. MB exerted greater inhibitions than MA but the mixture of MA and MB (1:1, v/v) possessed a similar level of inhibition to MB. On the other hand, although ME and 7KS presented non-significant inhibition, their mixture of ME-7KS (1:1, v/v) displayed a remarkable inhibition on the growth of S. altissima. Findings of this study revealed that MA, MB, and the mixture ME-7KS had the potential to control the invasive plant S. altissima and the noxious paddy weed E. crus-galli in vitro, but their mode of actions should be further investigated.

Potential Consequences of Hosting an Ant-tended Treehopper, Publilia concava, for Tall Goldenrod, Solidago altissima

In ant-hemipteran mutualisms, ‘tending’ ants indiscriminately defend hemipterans from other arthropods, protecting mutualism-hosting plants from defoliating herbivores in some cases. Censuses of a treehopper, Publilia concava, observations of tending ants, and measurements of leaf area were conducted on tall goldenrod, Solidago altissima, over the course of a summer at a field site in central Vermont. Hosting ant-tended treehopper aggregations had no effect on leaf area or the ability for goldenrod to flower, suggesting that in the absence of an herbivore outbreak this mutualism is neither necessary nor inherently detrimental for goldenrod. These findings support the hypothesis that the net consequence of the ant-hemipteran mutualism for its host plant depends on the costs of hemipteran damage, and the benefits of ant defense from other arthropods.