Observational evidence of herbivore‐specific associational effects between neighboring conspecifics in natural,dimorphic populations of Datura wrightii

Associational effects—in which the vulnerability of a plant to herbivores is influenced by its neighbors—have been widely implicated in mediating plant–herbivore interactions. Studies of associational effects typically focus on interspecific interactions or pest–crop dynamics. However, associational effects may also be important for species with intraspecific variation in defensive traits. In this study, we observed hundreds of Datura wrightii—which exhibits dimorphism in its trichome phenotype—from over 30 dimorphic populations across California. Our aim was to determine whether a relationship existed between the trichome phenotype of neighboring conspecifics and the likelihood of being damaged by four species of herbivorous insects. We visited plants at three timepoints to assess how these effects vary both within and between growing seasons. We hypothesized that the pattern of associational effects would provide rare morphs (i.e., focal plants that are a different morph than their neighbors) with an advantage in the form of reduced herbivory, thereby contributing to the negative frequency‐dependent selection previously documented in this system. We found the best predictor of herbivory/herbivore presence on focal plants was the phenotype of the focal plant. However, we also found some important neighborhood effects. The total number of plants near a focal individual predicted the likelihood and/or magnitude of herbivory by Tupiochoris notatus, Lema daturaphila, and Manduca sexta. We also found that velvety focal plants with primarily sticky neighbors are more susceptible to infestation by Tupiochoris notatus and Lema daturaphila. This does not align with the hypothesis that associational effects at the near‐neighbor scale contribute to a rare‐morph advantage in this system. Overall, the results of our study show that the number and trichome‐morph composition of neighboring conspecifics impact interactions between D. wrightii and insect herbivores.     

Sulfhydryl Localization and Tetrazolium Reduction. 1. Reversible Inhibition of its Reduction by N-Ethyl Maleimide

The sulfhydryl inhibitor N-ethyl maleimide completely inhibited the reduction of 2,3,5-triphenyltetrazolium chloride in meristematic and embryonic vascular tissues of Coleus sp. stems, Ricinus communis root tips, ungerminated Tea mays embryos, and epicotyls and coleoptiles of germinated Tea mays embryos, in a concentration of 200 mg/lit. Inhibition was reversed by the addition of cysteine or reduced glutathione (200 mg/lit) to the inhibitor medium. N-ethyl maleimide was effective also in blocking the nitro-prusside and 1-(4-chIoromercuriphenylazo)-naphthol-2 sulfhydryl staining reactions, but other substituted maleimides were ineffective in inhibiting the tetrazolium reaction in these tissues. Experiments were conducted to determine the histological pattern of sulfhydryl groups as indicated by a modification of the Bennett 1-(4-chloro-mercuriphenylazo)-naphthol-2 test and a modification of the Rap-kine nitroprusside test in certain plant tissues. A positive correlation was observed between tissues reducing the tetrazolium indicator and tissues exhibiting sulfhydryl localization as indicated by the nitroprusside reagent (trichloroacetic acid pretreated) and 1—(4— chloromercuriphenylazo)—naphthol—2.     

Wireless platform for controlled nitric oxide releasing optical fibers for mediating biological response to implanted devices

Despite the documented potential to leverage nitric oxide generation to improve in vivo performance of implanted devices, a key limitation to current NO releasing materials tested thus far is that there has not been a means to modulate the level of NO release after it has been initiated. We report the fabrication of a wireless platform that uses light to release NO from a polymethylmethacrylate (PMMA) optical fiber coated with an S-nitroso-N-acetylpenicillamine derivatized polydimethylsiloxane (SNAP-PDMS). We demonstrate that a VAOL-5GSBY4 LED (λ(dominant)=460nm) can be used as a dynamic trigger to vary the level of NO released from 500μm diameter coated PMMA. The ability to generate programmable sequences of NO flux from the surface of these coated fibers offers precise spatial and temporal control over NO release and provides a platform to begin the systematic study of in vivo physiological response to implanted devices. NO surface fluxes up to 3.88±0.57×10(-10)molcm(-2)min(-1) were achieved with ～100μm thick coatings on the fibers and NO flux was pulsed, ramped and held steady using the wireless platform developed. We demonstrate the NO release is linearly proportional to the drive current applied to the LED (and therefore level of light produced from the LED). This system allow the surface flux of NO from the fibers to be continuously changed, providing a means to determine the level and duration of NO needed to mediate physiological response to blood contacting and subcutaneous implants and will ultimately lead to the intelligent design of NO releasing materials tailored to specific patterns of NO release needed to achieve reliable in vivo performance for intravascular and subcutaneous sensors and potentially for a wide variety of other implanted biomedical devices.     

International Society for Reef Studies (ISRS)

International Society for Reef Studies (ISRS)     

International Society for Reef Studies (ISRS)

International Society for Reef Studies (ISRS)