Growth control by phytochrome of de-etiolated bean hypocotyls mediated by chlorophyll fluorescence

The elongation of hypocotyls excised from de-etiolated seedlings of beans (Phaseolus vulgaris L. cv. British Wax) is inhibited by light, blue and red irradiations being equally effective. Conditions which decrease chlorophyll fluorescence, such as CO₂-free air, abolish the inhibitory effect of blue irradiation and enhance the inhibition by red light. Conversely, conditions which increase chlorophyll fluorescence, such as a N₂ atmosphere or irradiation through a chlorophyll filter, abolish the inhibitory effect of red light and enhance the inhibition by blue irradiation. The inhibitory effect of blue light is reversible by red irradiation under increased fluorescence as well as by far red. We propose that the chlorophyll fluorescence excited by blue and red irradiations in λ_F > 660 nm and λ_F > 720 nm, respectively, is responsible for the inhibitory effect of blue light and the reduction of the inhibitory effect of non fluorescing red light. Both red and blue wavelengths seem, therefore, to control hypocotyl elongation through phytochrome.     

Virucidal Effect of Sodium p-Chloromercuribenzoate on Influenza Viruses Attributable to Inhibition of Virus Particle-Associated RNA-Dependent RNA Polymerase

Sodium p-chloromercuribenzoate (PCMB) caused a noticeable reduction of infectivity of prototype strains of type A and Lee strain of type B influenza viruses at concentrations of 100 and 200 μg/ml, respectively, after an incubation at 37 C for 60 min. The virucidal effect on A/AA/2/60 (H₂N₂) strain was dependent on the concentration of the drug and temperature as well as on the time of incubation. The reagent exerted this effect at a concentration which induced little change in the hemagglutinating and neuraminidase activities of the virus. PCMB inhibited by 50% the virus particle-associated RNA polymerase activity of all prototype strains of type A influenza virus at about 2 μg/ml and that of Lee strain of type B influenza virus at 8.5 μg/ml. Other sulfhydryl reagent such as phenylmercuric nitrate also exhibited virucidal effect on A/AA/2/60 virus which paralleled their inhibition of the virus particle-associated RNA polymerase activity. From these results it was considered likely that the virucidal action of PCMB on influenza viruses was attributable to inhibition of the virus particle-associated RNA polymerase activity.     

The effect of light quality on the induction of efficient photosynthesis under low CO2 conditions in Chlamydomonas reinhardtii and Chlorella pyrenoidosa

The effect of blue and red light on the adaptation to low CO₂ conditions was studied in high-CO₂ grown cultures of Chlorella Pyrenoidosa (82T) and Chlamydomonas reinhardtii(137⁺) by measuring O₂ exchange under various inorganic carbon (Cⁱ) concentrations. At equal photosynthetic photon flux density (PPFD), blue light was more favourable for adaptation in both species, compared to red light. The difference in photosynthetic oxygen evolution between cells adapted to low C_iunder blue and red light was more pronounced when oxygen evolution was measured under low C_i compared to high C_i conditions. The effect of light quality on adaptation remained for several hours. The different effects caused by blue and red light was observed in C. pyrenoidosa over a wide range of PPFD with increasing differences at increasing PPFD. The maximal difference was obtained at a PPFD above 1 500 μmol m^?2s^?1. We found no difference in the extracellular carbonic anhydrase activity between blue- and red light adapted cells. The light quality effect recorded under C_i-limiting conditions in C. reinhardtii cells adapted to air, was only 37% less when instead of pure blue light red light containing 12.5% of blue light (similar PPFD as blue light) was used during adaptation to low carbon. This indicates that in addition to affecting photosynthesis, blue light affected a sensory system involved in algal adaptation to low C_i conditions. Since the affinity for C_i of C. Pyrenoidosa and C. reinhardtii cells adapted to air under blue light was higher than that of cells adapted under red light, we suggest that induction of some component(s) of the C_i accumulating mechanism is regulated by the light quality.     

<Emphasis Type="Italic">In Vitro</Emphasis> antiviral activity of red alga, <Emphasis Type="Italic">Polysiphonia morrowii</Emphasis> extract and its bromophenols against fish pathogenic infectious hematopoietic necrosis virus and infectious pancreatic necrosis virus

Our previous investigation revealed that 80% methanolic extract of the red alga Polysiphonia morrowii has significant antiviral activities against fish pathogenic viruses, infectious hematopoietic necrosis virus (IHNV) and infectious pancreatic necrosis virus (IPNV). The present study was conducted to identify compounds attributed for its antiviral activities and investigate their antiviral activities against IHNV and IPNV. Activity-guided fractionation for 80% methanolic extract of Polysiphonia morrowii using a cell-based assay measuring virus-induced cytopathic effect (CPE) on cells yielded a 90% methanolic fraction, which showed the highest antiviral activity against both viruses among fractions yielded from the extract. From the fraction, two bromophenols were isolated and identified as 3-bromo-4,5-dihydroxybenzyl methyl ether (1) and 3-bromo-4,5-dihydroxybenzaldehyde (2) based on spectroscopic analyses. For both compounds, the concentrations to inhibit 50% of flounder spleen cell (FSP cell) proliferation (CC₅₀) and each viral replication (EC₅₀) were measured. In the pretreatment test, 3-bromo-4,5-dihydroxybenzyl methyl ether (1) and 3-bromo-4,5-dihy-droxybenzaldehyde (2) exhibited significant antiviral activities showing selective index values (SI = CC₅₀/EC₅₀) of 20 to 42 against both IHNV and IPNV. In direct virucidal test, 3-bromo-4,5-dihydroxybenzyl methyl ether (1) showed significant antiviral activités against both viruses while 3-bromo-4,5-dihydroxybenzaldehyde (2) was significantly effective against only IHNV. Although antiviral efficacies of both compounds against IHNV and IPNV were lower than those of ribavirin used as a positive control, our findings suggested that the red alga Polysiphonia morrowii and isolated two bromophenols may have potential as a therapeutic agent against fish viral diseases.     

Light and gibberellin-A3 interaction in the seedling growth ofAsteracantha longifolia nees. andRuellia tuberosa L.

Summary InA. longifolia andR. tuberosa, the radicle growth was inhibited and that of hypocotyl promoted in blue and red lights when compared with the white one. A distinct increase in hypocotyl growth took place in red and blue radiations as an interaction of gibberellin-A₃. Thus, this increase in hypocotyl growth in white light was distinct inA. longifolia for all the gibberellin-A₃ concentrations but only upto 10 ppm inR. tuberosa when compared with their controls. This was just reverse for those in total darkness. The beneficial effect of gibberellin-A₃ interaction on radicle growth was visible at 5 ppm in white light and at 10 ppm in red light forR. tuberosa; and only at 5 ppm in red light forA. longifolia.     

LIGHT ACTION SPECTRA OF N2 FIXATION BY HETEROCYSTOUS CYANOBACTERIA FROM THE BALTIC SEA1

An on‐line, laser photo‐acoustic, trace gas detection system in combination with a stepper motor‐controlled monochromator was used to record semicontinuous light action spectra of nitrogenase activity in heterocystous cyanobacteria. Action spectra were made of cultures of Nodularia spumigena Mertens ex Bornet & Flahault, Aphanizomenon flos‐aquae Ralfs ex Bornet & Flahault, and Anabaena sp. and from field samples of a cyanobacterial bloom in the Baltic Sea. Nitrogenase activity was stimulated by monochromatic light coinciding the red and blue peaks of chl a, the phycobiliproteins phycocyanin (allophycocyanin) and phycoerythrin, and several carotenoids. Because nitrogenase is confined to the heterocyst, it was concluded that all photopigments must have been present in these cells, were involved in light harvesting and photosynthesis, and supplied the energy for N₂ fixation. The species investigated showed marked differences in their nitrogenase action spectra, which might be related to their specific niches and to their success in cyanobacterial blooms. Moreover, light action spectra of nitrogenase activity shifted during the day, probably as the result of changes in the phycobiliprotein content of the heterocyst relative to chl a. Action spectra of nitrogenase and changes in pigment composition are essential for the understanding of the competitive abilities of species and for the estimation of N₂ fixation by a bloom of heterocystous cyanobacteria.     

Light-stimulated respiration in the green algaDunaliella tertiolecta: Involvement of the ultraviolet/blue-light photoreceptor(s) and phytochrome?

Starch breakdown and respiratory O₂ uptake in the green algaDunaliella tertiolecta (Butcher) are stimulated not only by blue, but also by red light. In the present study, attempts are described to identify the photoreceptor(s) involved. Fluence rate-response curves with different slopes in the ultraviolet (UV)/blue and in the red spectral region as well as differences in the kinetics and in the unfluence of dark pre-incubation on the stimulation of respiratory O₂ uptake by blue and red light strongly indicate the action of two photoreceptors. Since the effect of red light shows some far-red reversibility, and since simultaneous irradiation with red and far-red light decreases the effectiveness of red light, the involvement of phytochrome — in addition to the UV/blue photoreceptor(s) — is suggested in the light-stimulated respiration inDunaliella.Abbreviation UV ultraviolet     

Regulation of Transpiration in Avena. Responses to Red and Blue Light Steps

The transpiration responses of primary Arena leaves to red and blue light steps were investigated. The response to a red light step was a so-called slow response (with a rise time of about 8 min). The response to a blue light step consisted of both a slow, and a rapid response (with a rise time of about 2 min). CO₂-free air outside the leaf eliminated only the slow response, i.e. in CO₂-free ait the plant responded to blue light steps but not to red ones. A short exposure of red light prior to a blue light step enhanced the rapid response. The same enhancement of the rapid response could be achieved by means of a temporary pretreatment with CO₂-free air. The magnitude of the rapid response was dependent on the blue light irradiance and no threshold effects could be detected. — The experimental results are discussed by means of a model, based on stomatal regulation by, ion transport between the subsidiary cells and the guard cells. It is suggested that the slow transpiration response is due to CO₂-regulation of the stomatal aperture and that the rapid response reflect a CO₂-independent blue light sensitive process, which acts directly on the ion transport through the subsidiary and guard cell membranes.     

EFFECT OF TEMPERATURE ON THE SENSITIVITY OF NITROGENASE TO OXYGEN IN TWO HETEROCYSTOUS CYANOBACTERIA1

The effect of temperature and oxygen on nitrogenase activity in two heterocystous cyanobacteria, Anabaena variabilis Kütz. ATCC29413 and Nostoc sp. PCC7120, was investigated. The cyanobacteria were grown under a 12:12 light:dark (L:D) cycle at 27°C and were subsequently exposed to different temperatures (27, 36, 39, and 42°C) at different steady‐state O₂ concentrations (20, 10, 5, 0%). Light response curves of nitrogenase activity were recorded under each of these conditions using an online acetylene reduction assay combined with a sensitive laser photoacoustic ethylene detection method. The light response curves were fitted with the rectangular hyperbola model from which the model parameters N_m, N_d, and α were derived. In both strains, nitrogenase activity (N_tot = N_m + N_d) was the highest at 39°C–42°C and at 0% O₂. The ratio N_tot/N_d was 4.1 and 3.1 for Anabaena and Nostoc, respectively, indicating that respectively 25% and 33% of nitrogenase activity was supported by respiration (N_d). N_tot/N_d increased with decreasing O₂ concentration and with increasing temperature. Hence, each of these factors caused a relative increase in the light‐driven nitrogenase activity (N_m). These results demonstrate that photosynthesis and respiration both contribute to nitrogenase activity in Anabaena and Nostoc and that their individual contributions depend on both O₂ concentration and temperature as the latter may dynamically alter the flux of O₂ into the heterocyst.     

Cell expansion in the filamentous gametophyte of the fernOnoclea sensibilis L.

Filamentous gametophytes of the fernO. sensibilis were exposed to paired combinations of light of different qualities, hormones and cations in the attempt to elucidate the underlying processes that regulate cell expansion. Simultaneous treatments with high-pH buffers or the auxin antagonistp-chlorophenoxyisobutyric acid abolished blue-light-mediated expansion but did not influence growth in red light. In contrast, the red-light response was preferentially altered by the ethylene absorbant KMnO₄ or the Ca²⁺ chelator ethyleneglycol-bis(-aminoethyl ether) N,N-tetraacetic acid. The Ca²⁺ ionophore A23187 caused a significant reduction in cell expansion under both blue and red irradiation. A marked promotion of expansion was mediated by high concentrations of indole-3-acetic acid, but this effect was dependent on the presence of low-pH buffers. The ethylene-generating agent 2-chloroethylphosphonic acid decreased the magnitudes of both photoresponses; this inhibition was further enhanced by high Ca²⁺ concentrations. These findings and those with other plants are interpreted in terms of two independent control mechanisms for cell expansion: 1) a blue light photoreceptor-auxin-hydrogen ion system, and 2) a phytochrome-ethylene-calcium ion system.Abbreviations APW-X artificial pond water (the associated number designates pH) - CEPA 2-chloroethylphosphonic acid - EGTA ethyleneglycol-bis(-aminoethyl ether)N,N-tetraacetic acid - IAA indole-3-acetic acid - PCIB p-chlorophenoxyisobutyric acid     

Photon flux density and light quality induce changes in growth,stomatal development,photosynthesis and transpiration of <Emphasis Type="Italic">Withania Somnifera</Emphasis> (L.) Dunal. plantlets

The aim of the study was to establish whether the quantity and the quality of light affect growth and development of Withania somnifera plantlets. We have studied growth and histo-physiological parameters [stomatal characteristics, chloroplastic pigments concentrations, photosynthesis, and transpiration (E)] of W. somnifera plantlets regenerated under various light intensities, or monochromatic light or under a mixture of two colors of light in tissue culture conditions. Plantlets grown under a photon flux density (PFD) of 30 μmol m^-2 s^-1 showed greater growth and development than those raised under other PFDs. Chlorophylls and carotenoids, numbers of stomata, rate of photosynthesis (P_N) and transpiration (E), stomatal conductance (g_s), and water use efficiency (WUE) increased with increasing the PFD up to 60 μmol m^-2 s^-1. Light quality also affected plantlets growth and physiology. Highest growth was observed under fluorescent and in a mixture of blue and red light. Very few stomata were developed in any of the monochromatic light but under fluorescent or under a mixture of two colors stomatal numbers increased. Similarly, g_s, E, P_N, and WUE were also higher under fluorescent light and under a mixture of red and blue light. Regressional analysis showed a linear relationship between P_N (r ² = 70) and g_s and between E (r ² = 0.95) and g_s. In conclusion, both the quality and the quantity of light affect growth of plantlets, development of stomata and physiological responses differently depending on the intensity and the wavelength of light.     

Involvement of phytochrome and a blue light photoreceptor in UV-B induced flavonoid synthesis in parsley (Petroselinum hortense Hoffm.) cell suspension cultures

Flavonoid synthesis in cell suspension cultures of parsley (Petroselinum hortense Hoffm.) occurs only after irradiation with ultraviolet light (UV), mainly from the UV-B (280–320 nm) spectral range. However, it is also controlled by phytochrome. A P_fr/P_tot ratio of approximately 20% is sufficient for a maximum phytochrome response as induced by pulse irradiation. Continuous red and far red light, as well as blue light, given after UV, are more effective than pulse irradiations. The response to blue light is considerably greater than that to red and far red light. Continuous red and blue light treatments can be substituted for by multiple pulses and can thus probably be ascribed to a multible induction effect. Continuous irradiations with red, far red and blue light also increase the UV-induced flavonoid synthesis if given before UV. The data indicate that besides phytochrome a separate blue light photoreceptor is involved in the regulation of the UV-induced flavonoid synthesis. This blue light receptor seems to require the presence of P_fr in order to be fully effective.Abbreviations HIR high irradiance response - P_fr far red absorhing form of phytochrome - P_tet total phytochrome - UV ultraviolet light     

Green light drives photosynthesis in mosses

Temperate forests are characterised by variable light quality (i.e. spectral composition of light) at or near the forest floor. These understory environments have a high concentration of green light, as red and blue light are preferentially absorbed by upper canopy leaves. Understory species may be well-adapted for using green light to drive photosynthesis. Angiosperms have been shown to use green light for photosynthesis, but this ability has not been demonstrated in shade-dwelling bryophytes. In this study, net photosynthetic rate (P_N) of three temperate understory species of moss (Dichodontium pellucidum (Hedw.) Schimp., Leucobryum albidum (Brid. ex P.Beauv) Lindb. and Amblystegium serpens (Hedw.) Schimp.) was measured under green, red?+?blue, and red?+?blue?+?green light to assess green light use efficiency. All three species were capable of photosynthesising beyond their respiratory demands using solely green light, with higher green light use efficiency measured in plants collected from areas with greater canopy cover, suggesting growth in a green light concentrated environment increases green light use efficiency. Each species was also collected from sites differing in their degree of canopy cover and grown under three light treatments (high light, low light, and green light). Photosynthetic efficiency (chlorophyll fluorescence), tissue nitrogen and carbon isotope concentrations were assessed after a short growth period. Growth conditions had little effect on leaf chemistry and monochromatic green light did not significantly degrade photosynthetic efficiency. This study provides the first evidence to date of positive net ‘green light photosynthesis’ in mosses.     

Effect of light and gibberellic acid on coleoptile and first-foliage-leaf growth in durum wheat (Triticum durum Desf.)

A comparison has been made of the relative effectiveness of light quality and quantity and gibberellic acid (GA₃) treatment on the elongation growth of the coleoptile and the first foliage leaf in durum wheat (Triticum durum Desf. cvs. Cappelli and Creso). The cultivar Creso is a shortstrawed variety carrying the Gai 1 gene on chromosome 4A, which influences both plant height and insensitivity to applied gibberellins. The main conclusions are as follows: 1) coleoptile elongation growth appears to be modulated via the fluencerate-dependent action of a blue-light receptor and via a low energy response of phytochrome; 2) the inhibition of first-foliage-leaf growth depends on the operation of a single blue-light-responsive photoreceptor; 3) high energy blue light produces the same inhibitory effect on the two wheat cultivars, whereas at relatively low fluences of white and blue light, the cultivar Creso is more sensitive; 4) the insensitivity to applied GA₃ exerted by the gene Gai 1 in Creso is independent of light; 5) in Cappelli, the action of light on coleoptiles appears to be independent of the applied GA₃, whereas the hormone is able to change the pattern of growth inhibition of the first-foliage-leaf.Abbreviations BL blue light - FR far-red light - GA gibberellin - GA₃ gibberellic acid - R red light - WL white light     

Effect of long-term drought stress on leaf gas exchange and fluorescence parameters in C<Subscript>3</Subscript> and C<Subscript>4</Subscript> plants

A field study was performed on triticale, field bean, maize and amaranth, to find differences between studied species in physiological alterations resulting from progressive response as injuries and/or acclimation to long-term soil drought during various stages of plant development. The measurements of leaf water potential, electrolyte leakage, chlorophyll a fluorescence, leaf gas exchange and yield analysis were done. A special emphasis was given to the measurements of the blue, green, red and far-red fluorescence. Beside, different ratios of the four fluorescence bands (red/far-red: F ₆₉₀/F ₇₄₀, blue/red: F ₄₄₀/F ₆₉₀, blue/far-red: F ₄₄₀/F ₇₄₀ and blue/green: F ₄₄₀/F ₅₂₀) were calculated. Based on both yield analysis and measurements of physiological processes it can be suggested that field bean and maize responded with better tolerance to the water deficit in soil due to the activation of photoprotective mechanism probably connected with synthesis of the phenolic compounds, which can play a role of photoprotectors in different stages of plant development. The photosynthetic apparatus of those two species scattered the excess of excitation energy more effectively, partially through its transfer to PS I. In this way, plants avoided irreversible and/or deep injuries to PS II. The observed changes in the red fluorescence emission and in the F _v/F _m for triticale and amaranth could have occurred due to serious and irreversible photoinhibitory injuries. Probably, field bean and maize acclimatized more effectively to soil drought through the development of effective mechanisms for utilising excitation energy in the photosynthetic conversion of light accompanied by the mechanism protecting the photosynthetic apparatus against the excess of this energy.     

Induction mechanism of adventitious root from leaf explants of <Emphasis Type="Italic">Morinda citrifolia</Emphasis> as affected by auxin and light quality

An efficient protocol for adventitious root induction from leaf explants of Morinda citrifolia treated with different concentrations of indole-3-butyric acid (IBA) and α-naphthaleneacetic acid (NAA) was established in relation to physiological process changes during adventitious root induction under different light sources (fluorescent, red, blue, red + blue, and far-red). Among the different concentrations of IBA and NAA, 1.0 mg l⁻¹ IBA was proven as the best auxin source for adventitious root induction under fluorescent light. Higher concentrations of IBA and NAA trigger callus formation in both light and dark conditions. Maximum numbers of adventitious roots were induced under red light (26) followed by blue light (22) and the lowest under far-red light (6). In contrast, numerous callus formations were induced by red + blue followed by red and blue, while the highest root length (1.66 cm) with negligible callusing was observed under fluorescent light. Catalase and guaicacol peroxidase activities were highest under red light followed by fluorescent light and the lowest under red + blue light, but superoxide dismutase activity was not significantly influenced by different light sources. Ascorbate peroxidase played an important role in detoxification of the harmful effects of hydrogen peroxide (H₂O₂). Under fluorescent light, significantly lower accumulation of H₂O₂ was observed. Accumulation of H₂O₂ in the induced root under different light showed a positive correlation with peroxidation of lipids and was observed higher under far-red followed by red + blue and blue light.     

Effects of light and circadian clock on growth and chlorophyll accumulation of Nannochloropsis gaditana

Circadian clocks synchronize various physiological, metabolic and developmental processes of organisms with specific phases of recurring changes in their environment (e.g. day and night or seasons). Here, we investigated whether the circadian clock plays a role in regulation of growth and chlorophyll (Chl) accumulation in Nannochloropsis gaditana, an oleaginous marine microalga which is considered as a potential feedstock for biofuels and for which a draft genome sequence has been published. Optical density (OD) of N. gaditana culture was monitored at 680 and 735 nm under 12:12 h or 18:6 h light‐dark (LD) cycles and after switching to continuous illumination in photobioreactors. In parallel, Chl fluorescence was measured to assess the quantum yield of photosystem II. Furthermore, to test if red‐ or blue‐light photoreceptors are involved in clock entrainment in N. gaditana, some of the experiments were conducted by using only red or blue light. Growth and Chl accumulation were confined to light periods in the LD cycles, increasing more strongly in the first half than in the second half of the light periods. After switching to continuous light, rhythmic oscillations continued (especially for OD₆₈₀) at least in the first 24 h, with a 50% decrease in the capacity to grow and accumulate Chl during the first subjective night. Pronounced free‐running oscillations were induced by blue light, but not by red light. In contrast, the photosystem II quantum yield was determined by light conditions. The results indicate interactions between circadian and light regulation of growth and Chl accumulation in N. gaditana.     

Blue Light Induction of Barley Leaf Unfolding. A Phytochrome Reaction?

Low-energy blue light (450, 475 nm) has been found to induced unfolding of etiolated barley leaves (Hordeum rulgare cv. Ingrid). This induction can be reversed by far-red light. Barley leaf unfolding is normally stimulated by red light, reversed by far-red light, and can be considered to be a typical phytochrome controlled response. It is possible to explain the effects by red and blue light as mediated by the same photoreceptor. The phototransformation of this pigment results in two forms, P₂ and P₄, to which physiological activity can be ascribed. The red and blue light affect different steps in a cyclical photoconversion. Calculated theoretical dose response curves are presented for such a model in agreement with the experimental data.     

Effect of redox mediators on nitrogenase and hydrogenase activities in Azotobacter vinelandii

In bioelectrochemical studies, redox mediators such as methylene blue, natural red, and thionine are used to studying the redox characteristics of enzymes in the living cell. Here we show that nitrogenase activity in Azotobacter vinelandii is completely inhibited by oxidized methylene blue (MB_o) when the concentration of this mediator in the medium is increased up to 72 M. This activity in A. vinelandii is somewhat inhibited by a coenzyme, ascorbic acid (AA). However, the nitrogenase activity within the A. vinelandii cell is unchanged even for a high concentration of oxidized natural red (NR_o) alone. Interestingly, these mediators and AA do not have the capacity to inhibit the H₂ uptake activity of the hydrogenase in A. vinelandii. Average active rates of 66 nM H₂ evolved/mg cell protein/min from the nitrogenase and 160 nM H₂-uptake/mg cell protein/min from the hydrogenase in A. vinelandii are found in aid of the activities of the enzymes for H₂ evolution and for H₂ uptake are compared. The activities of both enzymes in A. vinelandii are strongly inhibited by thionine having high oxidative potential. Mechanisms of various mediators acting in vivo for both enzymes in A. vinelandii are discussed.     

Discriminative detection of mercury (II) and hydrazine using a dual‐function fluorescent probe

A dual‐function fluorescent probe (Probe 1 ) was developed for discriminative detection of Hg²⁺ and N₂H₄. Probe 1 could discriminatively detect Hg²⁺ and N₂H₄ through two different reaction sites, with the mechanism for Probe 1 for Hg²⁺ depending on a desulfurization reaction and for N₂H₄ depending on the Schiff‐base reaction. N₂H₄ had minimal effect on Hg²⁺ detection in dimethyl sulfoxide (DMSO)/H₂O solution, but Hg²⁺ could interfere with N₂H₄ detection in DMSO/buffer solution. Different concentrations of Hg²⁺ and N₂H₄ resulted in different blue shades of Probe 1 test strips, and the shade of blue was different with the same concentration of Hg²⁺ or N₂H₄, as observed under ultraviolet light at 365 nm wavelength.