Determination of indole-3-acetic acid in soil using excitation-emission matrix fluorescence with trilinear decomposition-based calibration methods

Chitosan Induces Plant Hormones and Defenses in Tomato Root Exudates

In this work, we use electrophysiological and metabolomic tools to determine the role of chitosan as plant defense elicitor in soil for preventing or manage root pests and diseases sustainably. Root exudates include a wide variety of molecules that plants and root microbiota use to communicate in the rhizosphere. Tomato plants were treated with chitosan. Root exudates from tomato plants were analyzed at 3, 10, 20, and 30 days after planting (dap). We found, using high performance liquid chromatography (HPLC) and excitation emission matrix (EEM) fluorescence, that chitosan induces plant hormones, lipid signaling and defense compounds in tomato root exudates, including phenolics. High doses of chitosan induce membrane depolarization and affect membrane integrity. 1H-NMR showed the dynamic of exudation, detecting the largest number of signals in 20 dap root exudates. Root exudates from plants irrigated with chitosan inhibit ca. twofold growth kinetics of the tomato root parasitic fungus Fusarium oxysporum f. sp. radicis-lycopersici. and reduced ca. 1.5-fold egg hatching of the root-knot nematode Meloidogyne javanica.

Simultaneous analysis of thirteen phytohormones in fruits and vegetables by SPE-HPLC-DAD

Determination of phytohormones have attracted increasing attentions in food safety field. In this study, an efficient and quantitative method was developed which can simultaneously determinate thirteen phytohormones in fruits and vegetables using solid phase extraction (SPE) combined with high performance liquid chromatography-diode array detection (HPLC-DAD). The samples were extracted with 80% methanol containing 0.5% (V/V) formic acid, and the extracts were then concentrated and purified using primary secondary amine (PSA) and C18 tandem dual SPE cartridges. The analytes were separated on a Waters XBridge™ C18 column and eluated utilizing a gradient elution program of water and methanol. Mean recoveries of the thirteen analytes varied from 74.69 to 92.40%, with relative standard deviations < 3.57%. The limits of detection and quantitation were 0.005-0.018 mg/kg and 0.02-0.10 mg/kg, respectively. The phytohormones in kiwi fruit, strawberry, bean sprout, and green pepper were detected using the above method, respectively. Only the IAA content of 0.14 mg/kg was detected for the strawberry from a supermarket, which was lower than the prescribed limit in food safety standards (0.2 mg/kg).

Disposable stainless steel-based electrochemical microsensor for in vivo determination of indole-3-acetic acid in soybean seedlings

In vivo detecting of plants signal molecules is of great importance for the precision farming, crop management and plant phenotyping. In this work, for in vivo detecting indole-3-acetic acid (IAA), one of phytohormones, fine stainless steel (SS) wire was used as electrode material. Highly ordered nanopores, popcorn-like Au nanostructures, Pt nanoparticles and reduced graphene oxide (ERGO) nanocomposite films, and polymerized ST film (PST) were fabricated on the SS microelectrode in turn for improving the detection effect. Using the as-prepared SS microelectrode as working electrode, two untreated SS wires as reference electrode and counter electrode respectively, a disposable electrochemical microsensor for IAA were developed. The microsensor exhibited excellent selectivity and high sensitivity with low detection limit (LOD) of 43 pg mL-1. The limit of quantity (LOQ) is 143 pg mL-1. The RSD was 7% for 12 different PST/Pt-ERGO/Au/a-SS microsensors in presence of 100 µg mL-1 IAA. Using this microsensor, IAA of the stem of soybean seedlings was detected in vivo under salt stress. Our result was also confirmed by ultra-performance liquid chromatography-mass spectrum (UPLC-MS). This is the first report for the in vivo detection of IAA in plants using SS-based electrochemical microsensor. Our sensor provides an excellent sensing platform for detecting IAA in plants in vivo.

Chemical pre-reduction and electro-reduction guided preparation of a porous graphene bionanocomposite for indole-3-acetic acid detection

A porous graphene (PG) bionanocomposite of PG, gold nanoparticles (AuNPs) and anti-indole-3-acetic acid (anti-IAA) antibody for sensitive and label-free amperometric immunoassay of IAA was reported. A PG film was produced by a pre-reduction/electrochemical reduction process on a glassy carbon electrode (GCE) and then a homogeneous AuNPs layer electrodeposition on the PG film. The anti-IAA antibody was immobilized onto the AuNPs through electrostatic adsorption and covalent conjugation. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), elecro-chemical impedance spectroscopy (EIS), ultraviolet visible spectroscopy (UV-vis) and differential pulse voltammetry (DPV) were used to characterize the PG film and the stepwise modification of the immunosensor. The electrochemical immunosensor exhibited a wide linear range from 2 × 10-11 to 2 × 10-8 g mL-1 with a detection limit of 0.016 ng mL-1 (S/N = 3) and showed significant linearity R2 = 0.9970. In addition, the proposed immunosensor showed acceptable selectivity and has been applied to the determination of IAA in the extract samples of several plant seeds with acceptable relative derivation (%) ranging from -5.25% to 4.24% between the immunosensor and high performance liquid chromatography. The proposed chemical pre-reduction and electro-reduction guided protocol can be extended to the preparation of many other functionalized PG nanocomposite films for wide applications.

A highly sensitive electrochemical impedance immunosensor for indole-3-acetic acid and its determination in sunflowers under salt stress

A novel label-free electrochemical impedance immunosensor for IAA determination has been developed based on PAMAM and anti-IAA–AuNP complexes.

Simultaneous analysis of ten phytohormones in Sargassum horneri by high-performance liquid chromatography with electrospray ionization tandem mass spectrometry

Phytohormones have attracted wide attention due to their important biological functions. However, their detection is still a challenge because of their complex composition, low abundance and diverse sources. In this study, a novel method of high-performance liquid chromatography with electrospray ionization tandem mass spectrometry was developed and validated for the simultaneous determination of ten phytohormones including indole-3-acetic acid, isopentenyladenine, isopentenyl adenosine, trans-zeatin riboside, zeatin, strigolactones, abscisic acid, salicylic acid, gibberellin A3, and jasmonic acid in Sargassum horneri (S. horneri). The phytohormones were extracted from freeze-dried S. horneri with methanol/water/methanoic acid (15:4:1, v/v/v) analyzed on a Hypersil Gold C18 column and detected by electrospray ionization tandem triple quadrupole mass spectrometry in the multiple reaction monitoring mode. The experimental conditions for the extraction and analysis of phytohormones were optimized and validated in terms of reproducibility, linearity, sensitivity, recovery, accuracy, and stability. Distributions of the phytohormones in the stems, blades, and gas bladder of the S. horneri in drift, fixed, and semi-fixed growing states were investigated for the first time. The observed contents of the phytohormones in S. horneri range from not detected to 5066.67 ng/g (fresh weight). Most phytohormones are distributed mainly in the stems of S. horneri in drift and semi-fixed states.

Quantitative study of state switching in proteins using a single probe combined with trilinear decomposition

Excitation–Emission Matrix fluorescence (EEM) signals from the state switching of α-chymotrypsin can be resolved and investigated quantitatively by trilinear decomposition.

Analytical methods for tracing plant hormones

Plant hormones play important roles in regulating numerous aspects of plant growth, development, and response to stress. In the past decade, more analytical methods for the accurate identification and quantitative determination of trace plant hormones have been developed to better our understanding of the molecular mechanisms of plant hormones. As sample preparation is often the bottleneck in analysis of plant hormones in biological samples, this review firstly discusses sample preparation techniques after a brief introduction to the classes, roles, and methods used in the analysis of plant hormones. The analytical methods, especially chromatographic techniques and immuno-based methods, are reviewed in detail, and their corresponding advantages, limitations, applications, and prospects are also discussed. This review mainly covers reports published from 2000 to the present on methods for the analysis of plant hormones.

Interference-free determination of and in plant samples using excitation-emission matrix fluorescence based on oxidationderivatization coupled with second-order calibration methods

A sensitive excitation-emission fluorescence method with a second-order calibration strategy is proposed to simultaneously determine abscisic acid (ABA) and gibberellin (GA) contents in extracts of leaves and buds of ginkgo. The methodology is based on the alternating normalization-weighed error (ANWE) and the parallel factor analysis (PARAFAC) algorithms, which make it possible that the ABA and GA concentration can be attained in extract of plants even in the presence of unknown interference from potential interfering matrix contaminants introduced during the simple pretreatment procedure. Satisfactory recoveries were obtained although the excitation and emission profiles of the analytes were heavily overlapped with each other and the background in the extracts. The limits of detection obtained for GA and ABA in leaf samples were 9.6 and 6.9 ng mL-1, respectively, which were in the concentration range (from hundreds to several ng g-1) for GA and ABA in leaves in different periods. Furthermore, in order to investigate the performance of the developed method, some statistical parameters and figures of merit of ANWE and PARAFAC are evaluated. The method proposed lights a new avenue to determine quantitatively phytohormones in extracts of plants with a simple pretreatment procedure, and may hold potential to be extended as a promising alternative for more practical applications in plant growth processes.