A highly sensitive hydrogen peroxide probe that takes advantage of the amplified fluorescence quenching of conjugated polymers has been developed. The cationic conjugated polymer, poly(9,9‐bis(6′‐N,N,N‐trimethylammonium‐hexyl) fluorene phenylene) (PFP‐NMe3+) and peroxyfluor‐1 with boronate protecting groups (Fl‐BB) are used to detect H2O2 optically. Without the addition of H2O2, the absence of electrostatic interactions between the cationic PFP‐NMe3+ and the neutral Fl‐BB keeps the Fl‐BB well separated from the PFP‐NMe3+, and no fluorescence quenching of the PFP‐NMe3+ occurs. In the presence of H2O2, the formation of the anionic quencher, fluorescein, by specific reaction of the Fl‐BB with H2O2 results in strong electrostatic interactions between the PFP‐NMe3+ and the fluorescein, and therefore efficient fluorescence quenching of the PFP‐NMe3+ occurs. The absorption of fluorescein overlaps the emission of PFP‐NMe3+, which encourages fluorescence resonance energy transfer (FRET) from the PFP‐NMe3+ to the fluorescein. The H2O2 probe has very good sensitivity, with a detection range of 15 to 600 nM. Since glucose oxidase (GOx) can specifically catalyze the oxidation of β‐D‐(+)‐glucose to generate H2O2, glucose detection is also realized with the H2O2 probe as the signal transducer.
The plastic responses of plants to abiotic and biotic environmental factors have generally been addressed separately; thus we have a poor understanding of how these factors interact. For example, little is known about the effects of plant–plant interactions on the plasticity of plants in response to water availability. Furthermore, few studies have compared the effects of intra‐ and interspecific interactions on plastic responses to abiotic factors. To explore the effects of intraspecific and interspecific plant–plant interactions on plant responses to water availability, we grew Leucanthemum vulgare and Potentilla recta with a conspecific or the other species, and grew pairs of each species as controls in pots with the roots, but not shoots, physically separated. We subjected these competitive arrangements to mesic and dry conditions, and then measured shoot mass, root mass, total mass and root : shoot ratio and calculated plasticity in these traits. The total biomass of both species was highly suppressed by both intra‐ and interspecific interactions in mesic soil conditions. However, in drier soil, intraspecific interactions for both species and the effect of P. recta on L. vulgare were facilitative. For plasticity in response to water supply, when adjusted for total biomass, drought increased shoot mass, and decreased root mass and root : shoot ratios for both species in intraspecific interactions. When grown alone, there were no plastic responses in any trait except total mass, for either species. Our results suggested that plants interacting with other plants often show improved tolerance for drought than those grown alone, perhaps because of neighbor‐induced shifts in plasticity in biomass allocation. Facilitative effects might also be promoted by plasticity to drought in root : shoot ratios.
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