Potential Plant Growth Regulators Research Articles

Cultivating Pharmaceutical Potential: Optimising Triacontanol Application to Enhance Linseed’s Attributes under Drought Stress

Background: Triacontanol (TRIA) has been identified as a potent plant growth regulator, demonstrating significant benefits under various stress conditions. However, its specific impact on Linum usitatissimum L. (flax) under drought stress conditions remains underexplored. This study investigates the effects of TRIA on the growth, physiology, and biochemistry of two flax genotypes subjected to drought stress, aiming to enhance our understanding of its potential as a biostimulant for improving crop resilience and productivity. Objective: The primary objective of this study was to evaluate the effects of different concentrations of TRIA on the growth, physiological, and biochemical responses of two flax genotypes under drought stress conditions. We aimed to determine whether TRIA application could mitigate the adverse effects of drought and enhance plant performance. Methods: This study was conducted using two flax genotypes, G-20888 and G-22186. Plants were grown under controlled conditions and subjected to drought stress by maintaining soil moisture at 50% field capacity. TRIA was applied in three concentrations: 0 M (control), 10^-6 M, and 10^-7 M. A completely randomized design was used with three replications for each treatment. Plant growth parameters, including root length, shoot length, plant height, and shoot fresh weight, were measured. Physiological parameters such as chlorophyll content, relative water content (RWC), and electrolyte leakage were assessed. Biochemical analyses included the estimation of antioxidant enzyme activities (superoxide dismutase, catalase, and peroxidase). Data were statistically analyzed using SPSS version 25.0. Results: TRIA application significantly improved root length, shoot length, plant height, and shoot fresh weight in both flax genotypes under drought stress. For genotype G-20888, root length increased from 5.1 cm (control) to 6.8 cm (TRIA 10^-7 M). Shoot length showed a similar trend, with increases from 8.3 cm (control) to 10.1 cm (TRIA 10^-7 M). In G-22186, plant height increased from 70 cm (control) to 82 cm (TRIA 10^-7 M). Chlorophyll content increased by 15%, and RWC by 18% in TRIA-treated plants compared to controls. Antioxidant enzyme activities were also enhanced, with catalase activity increasing by 25% and peroxidase by 30%. Conclusion: TRIA application significantly mitigated the adverse effects of drought stress on flax genotypes by enhancing growth, physiological, and biochemical parameters. The findings suggest that TRIA could be an effective biostimulant for improving drought tolerance in flax, potentially leading to better crop resilience and productivity.

Enhancement of soybean tolerance to water stress through regulation of nitrogen and antioxidant defence mechanisms mediated by the synergistic role of salicylic acid and thiourea

Water stress (WS) poses a significant threat to global food and energy security by adversely affecting soybean growth and nitrogen metabolism. This study explores the synergistic effects of exogenous salicylic acid (SA, 0.5 mM) and thiourea (TU, 400 mg L−1), potent plant growth regulators, on soybean responses under WS conditions. The treatments involved foliar spraying for 3 days before inducing WS by reducing soil moisture to 50% of field capacity, followed by 2 weeks of cultivation under normal or WS conditions. WS significantly reduced plant biomass, chlorophyll content, photosynthetic efficiency, water status, protein content, and total nitrogen content in roots and leaves. Concurrently, it elevated levels of leaf malondialdehyde, H2O2, proline, nitrate, and ammonium. WS also triggered an increase in antioxidant enzyme activity and osmolyte accumulation in soybean plants. Application of SA and TU enhanced the activities of key enzymes crucial for nitrogen assimilation and amino acid synthesis. Moreover, SA and TU improved plant growth, water status, chlorophyll content, photosynthetic efficiency, protein content, and total nitrogen content, while reducing oxidative stress and leaf proline levels. Indeed, the simultaneous application of SA and TU demonstrated a heightened impact compared to their separate use, suggesting a synergistic interaction. This study underscores the potential of SA and TU to enhance WS tolerance in soybean plants by modulating nitrogen metabolism and mitigating oxidative damage. These findings hold significant promise for improving crop productivity and quality in the face of escalating water limitations due to climate change.

Oxidized of chitosan with different molecular weights for potential antifungal and plant growth regulator applications

The application of Chitosan (CS) in drug delivery systems, plant growth promotion, antibacterial potentiality and plant defense is significantly limited by its inability to dissolve in neutral solutions. In this work, CS with different molecular weights (Mw) has been oxidized, yielding five kinds of oxidized chitosan (OCS 1–5) with solubilities in neutral solutions. The results obtained from Fourier Transform Infrared Spectroscopy clearly showed the successful oxidation of the hydroxyl group to form aldehyde and carboxyl groups. And the CS derivatives showed the wrinkled and lamellar structures on the surface of OCS. The results of antifungal activity against Fusarium graminearum showed that the OCS dissolved in 2 % (V/V) acetic acid exhibited better performance of almost complete inhibition of mycelial growth compared with CS at the concentration of 500 μg/mL. Among the five OCS, OCS-4 exhibited the best antifungal effect and had the lowest EC50 value of 581.68 μg/mL in samples. OCS-4 displayed superior promoting effect on seed germination with a germination potential of 62.2 % at a concentration of 3 g/L and a germination rate of 74.5 %. Additionally, the other four OCS also showed excellent antifungal activity with dose-dependent manners. These results indicated that the OCS had excellent antifungal potential in agricultural production.

Melatonin supplementation combats nickel-induced phytotoxicity in Trigonella foenum-graecum L. plants through metal accumulation reduction, upregulation of NO generation, antioxidant defence machinery and secondary metabolites

Nickel (Ni) at a toxic level (80 mg kg−1 of soil) adversely affects the crop performance of fenugreek (Trigonella foenum-graecum L.). Melatonin (MEL), a potent plant growth regulator, is ascribed to offer promising roles in heavy metal stress alleviation. In this study, different doses viz. 0, 25, 50, 75 and 100 μM of MEL were administered to plants through foliage under normal and Ni-stress conditions. The experiment unveiled positive roles of MEL in enhancing root-shoot lengths, fresh-dry weights, seed yield and restoring photosynthetic efficiency assessed in terms of higher Fv/Fm, YII, qP, and lower NPQ values in plants exposed to Ni (80 mg kg−1). MEL supplementation (at 75 μM) effectively restricted Ni accumulation and regulated oxidative stress via modulation of MDA, O2−, H2O2 and NO generation, most prominently. Besides, MEL at 75 μM more conspicuously perked up the activities of antioxidant enzymes like SOD, POX, CAT and APX by 15.7, 20.0, 14.5 and 16.5% higher than the Ni-exposed plants for effective ROS scavenging. Likewise, MEL at 75 μM also efficiently counteracted Ni-generated osmotic stress, through an upscaled accumulation of proline (19.6%) along with the enhancement in the concentration of total phenols (13.6%), total tannins (11.2%), total flavonoids (25.5%) and total alkaloids (19.2%) in plant's leaves. Furthermore, under 80 mg kg−1 Ni stress, MEL at 75 μM improved the seed's trigonelline content by 40.1% higher compared to Ni-disturbed plants, upgrading the pharmacological actions of the plant. Thus, the present study deciphers the envisaged roles of MEL in the alleviation of Ni stress in plants to enhance overall crop productivity.

The Synthesis of 1-Alkyl-3-polyfluoroalkyl- 1,3-dihydrobenzimidazole-2-selenones as Potential Plant Growth Regulators

Aim. To synthesize new 1-alkyl-3-polyfluoroalkyl-1,3-dihydrobenzimidazole-2-selenones and study their biological activity as potential plant growth regulators.Results and discussion. 1-Alkyl-3-polyfluoroalkyl-1,3-dihydrobenzimidazole-2-selenones were obtained from the corresponding 1-alkyl-3-polyfluoroalkylbenzimidazolium iodides by the action of elemental selenium in the presence of a base. The preliminary biological tests for the growth-regulating activity of the compounds obtained were conducted.Experimental part. The structure of the compounds synthesized was proven by 1H and 19F NMR spectroscopy methods, as well as by the elemental analysis. The biological studies were done on model plants of winter wheat of the “bezosta” variety.Conclusions. A convenient method for obtaining 1-alkyl-3-polyfluoroalkyl-1,3-dihydro-benzimidazole-2-selenones has been developed. Biological studies have shown that the compounds synthesized have a diverse effect on the plant growth.

Discovery of Novel Hybrid-Type Strigolactone Mimics Derived from Cinnamic Amide.

Strigolactones (SLs) are a class of plant hormones and rhizosphere communication signals of great interest. They perform diverse biological functions including the stimulation of parasitic seed germination and phytohormonal activity. However, their practical use is limited by their low abundance and complex structure, which requires simpler SL analogues and mimics with maintained biological function. Here, new, hybrid-type SL mimics were designed, derived from Cinnamic amide, a new potential plant growth regulator with good germination and rooting-promoting activities. Bioassay results indicated that compound 6 not only displayed good germination activity against the parasitic weed O. aegyptiaca with an EC50 value of 2.36 × 10-8 M, but also exhibited significant inhibitory activity against Arabidopsis root growth and lateral root formation, as well as promoting root hair elongation, similar to the action of GR24. Further morphological experiments on Arabidopsis max2-1 mutants revealed that 6 possessed SL-like physiological functions. Furthermore, molecular docking studies indicated that the binding mode of 6 was similar to that of GR24 in the active site of OsD14. This work provides valuable clues for the discovery of novel SL mimics.

Ethylidene-Tethered Chromene-Pyrone Hybrids as Potential Plant-Growth Regulators from an Endolichenic Phaeosphaeria Species.

Phaeosphaeria sp., a lichen-associated fungus, produced six skeletally new dimeric spiciferones (1-6) and four known metabolites (7-10). The new structures were elucidated by spectroscopic analysis, and their absolute configurations were determined by electronic circular dichroism calculations. Compounds 1 and 3-6 represent the first examples of ethylidene-bridged dimers from the building blocks 4H-chromene-4,7(8H)-dione and α-pyrone, and 2 is a unique homodimer of spiciferone. Compounds 1, 2, and 5-9 significantly inhibited the growth of weed-like dicot Arabidopsis thaliana at 100.0 μM. Notably, 8 showed the strongest inhibitory activity against the fresh weight and root elongation of A. thaliana with the IC50 values of 32.04 and 26.78 μM, respectively, whereas 1, 8, and 9 stimulated the growth of A. thaliana at lower concentrations. Meanwhile, compounds 2 and 6 exhibited weak inhibitory effects on the root elongation of monocot rice, while 1 and 8 exhibited growth-promoting effects on the shoot and root elongation of rice in a roughly dose-dependent manner.

Polyamines inhibit abscisic acid-induced stomatal closure by scavenging hydrogen peroxide.

Stomatal closure is regulated by plant hormones and some small molecules to reduce water loss under stress conditions. Both abscisic acid (ABA) and polyamines alone induce stomatal closure; however, whether the physiological functions of ABA and polyamines are synergistic or antagonistic with respect to inducing stomatal closure is still unknown. Here, stomatal movement in response to ABA and/or polyamines was tested in Vicia faba and Arabidopsis thaliana, and the change in the signalling components under stomatal closure was analysed. We found that both polyamines and ABA could induce stomatal closure through similar signalling components, including the synthesis of hydrogen peroxide (H2 O2 ) and nitric oxide (NO) and the accumulation of Ca2+ . However, polyamines partially inhibited ABA-induced stomatal closure both in epidermal peels and in planta by activating antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), to eliminate the ABA-induced increase in H2 O2 . These results strongly indicate that polyamines inhibit abscisic acid-induced stomatal closure, suggesting that polyamines could be used as potential plant growth regulators to increase photosynthesis under mild drought stress. This article is protected by copyright. All rights reserved.

Uniconazole and Adaptability of Transplantations by Enhancing the Competition Tolerance in a High Sowing Density of Rapeseed Blanket Seedlings

Having nursery rapeseed (Brassica napus L.) seedlings at a high density in a tray is an indispensable step to realizing mechanized transplanting for rapeseed. The reduction in seedling quality caused by high sowing density is one of the key factors affecting transplanting quality and yield. Uniconazole has been considered as a potential plant growth regulator to improve plant growth under diverse unfavorable circumstances. In two sowing densities (400 and 800 seeds per tray), an experiment was carried out between 2021 and 2022 to investigate the effects of uniconazole seed-coating treatments on pre-transplant and post-transplant seedling characteristics. The results demonstrate that uniconazole treatment can effectively reduce the high-density-induced reduction in seedling dry matter and leaf area, stem thinness, and stem and petiole overgrowth. Further evidence that uniconazole can improve seedling quality, enhance yield, and lessen yield loss due to high-density sowing was provided by yield at maturity. However, because of the uncontrolled growth during the late stage in the tray, the relative growth rate of seedlings after transplant in the transplant shock stage revealed that lower doses of uniconazole treatment have a negative effect on the seedling recovery. The results of principal coordinate analysis and partial correlation analysis proved that the yield and net assimilation rate were related to the improvement of seedling high-density tolerance by uniconazole treatment. Consequently, 500–750 mg L−1 uniconazole coating per 100 g of seeds in 5 mL is recommended by this study, considering the potential risk of seedling emergence and growth caused by an overdose of uniconazole treatment.

Photostable Abscisic Acid Agonists with a Geometrically Rigid Cyclized Side Chain.

The plant hormone abscisic acid (ABA) plays a central role in adaptive responses to abiotic stresses that adversely affect crop growth and productivity. However, ABA photoinstability limits its use in agriculture. To overcome this drawback, in this study, we developed photostable ABA analogues, the (+)-BP2A compound series (compounds 5-9), in which the dienoic acid side chain of ABA was replaced with phenylacetic acid. All BP2A analogues showed higher stability against UV-B irradiation at 302 nm than ABA, and compounds 6 and 7 barely decomposed even under sunlight. In physiological assays, (+)-BP2A and (+)-compound 7, in which the α,β-unsaturated carbonyl group of BP2A was reduced, exhibited ABA-like activities, including inhibition of seed germination and induced drought tolerance in Arabidopsis. Biochemical studies revealed that (+)-compound 7, unlike (+)-BP2A, did not activate pyrabactin resistance-like (PYL) receptors in vitro and was converted to (+)-BP2A in plants, suggesting that it functions as a prodrug PYL agonist. Furthermore, (+)-compound 7 inhibited seed germination of tomato, lettuce, and rice. Thus, this compound represents a potential plant growth regulator that induces ABA-type responses in agricultural fields.

Advances in 5-Aminolevulinic Acid Priming to Enhance Plant Tolerance to Abiotic Stress.

Priming is an adaptive strategy that improves plant defenses against biotic and abiotic stresses. Stimuli from chemicals, abiotic cues, and pathogens can trigger the establishment of priming state. Priming with 5-aminolevulinic acid (ALA), a potential plant growth regulator, can enhance plant tolerance to the subsequent abiotic stresses, including salinity, drought, heat, cold, and UV-B. However, the molecular mechanisms underlying the remarkable effects of ALA priming on plant physiology remain to be elucidated. Here, we summarize recent progress made in the stress tolerance conferred by ALA priming in plants and provide the underlying molecular and physiology mechanisms of this phenomenon. Priming with ALA results in changes at the physiological, transcriptional, metabolic, and epigenetic levels, and enhances photosynthesis and antioxidant capacity, as well as nitrogen assimilation, which in turn increases the resistance of abiotic stresses. However, the signaling pathway of ALA, including receptors as well as key components, is currently unknown, which hinders the deeper understanding of the defense priming caused by ALA. In the future, there is an urgent need to reveal the molecular mechanisms by which ALA regulates plant development and enhances plant defense with the help of forward genetics, multi-omics technologies, as well as genome editing technology.

Effect of 2,4-Dichlorophenoxy Acetic Acid and Activated Charcoal on Callus Induction of Cocos Nucifera L. Hybrid MATAG Inflorescence

Cocos Nucifera Linn. Var. MATAG is a Dwarf coconut variety that had high demand in Malaysia but low supply. Vegetative propagation of high-yielding MATAG coconut by using in vitro cloning must be considered in contributing to increase coconut productivity. Thus, attempts were made to develop a protocol that would enhance callogenesis as a first preliminary step towards a protocol for mass propagation of C. nucifera L. var. MATAG. The anther isolated from immature inflorescence was used as explants and cultured on modified Eeuwens Y3 media in different concentrations of 2,4-dicholorophenoxy acetic acid (2,4-D) and activated charcoal. The highest callus induction percentage (31.25 ± 12.18) was observed in 20 mg/L 2,4-D. However, 2,4-D at any level tested were not statistically significant. Callus induction media supplemented with 0.5 mg/L activated charcoal gave the highest callusing percentage (25.89 ± 13.59 %) indicating a positive effect of activated charcoal on callusing even though the result obtained not significant compared to control (15.95 ± 6.76 %). But, activated charcoal supplemented in media produced a significant effect compared to control in reducing the percentage of browning. In conclusion, media supplemented with activated charcoal produced a higher rate on callus induction and preventing tissue browning in explant. Besides that, the anther and ovule explant may serve as an efficient explant to study the callus induction of C. nucifera L. var. MATAG and as a basis to screen the potential useful plant growth regulators for somatic embryogenesis.

Ameliorative effect of melatonin improves drought tolerance by regulating growth, photosynthetic traits and leaf ultrastructure of maize seedlings

BackgroundMelatonin is considered a potential plant growth regulator to enhance the growth of plants and increase tolerance to various abiotic stresses. Nevertheless, melatonin’s role in mediating stress response in different plant species and growth cycles still needs to be explored. This study was conducted to understand the impact of different melatonin concentrations (0, 50, 100, and 150 μM) applied as a soil drench to maize seedling under drought stress conditions. A decreased irrigation approach based on watering was exposed to maize seedling after drought stress was applied at 40–45% of field capacity.ResultsThe results showed that drought stress negatively affected the growth behavior of maize seedlings, such as reduced biomass accumulation, decreased photosynthetic pigments, and enhanced the malondialdehyde and reactive oxygen species (ROS). However, melatonin application enhanced plant growth; alleviated ROS-induced oxidative damages by increasing the photosynthetic pigments, antioxidant enzyme activities, relative water content, and osmo-protectants of maize seedlings.ConclusionsMelatonin treatment also enhanced the stomatal traits, such as stomatal length, width, area, and the number of pores under drought stress conditions. Our data suggested that 100 μM melatonin application as soil drenching could provide a valuable foundation for improving plant tolerance to drought stress conditions.

Discovery of novel potential plant growth regulators from Corydalis mucronifera

Three pairs of enantiomers mucroniferals A-C (1–3), with a novel skeleton of 1,4-epoxynaphthalene-2,3-dicarboxylic acid first reported from nature source, were isolated from Corydalis mucronifera. Their structures were elucidated based on extensive spectroscopic data analysis of MS, 1D and 2D NMR, and their absolute configurations were confirmed by single-crystal X-ray diffraction analysis and comparison of the experimental and calculated ECD data. Mucroniferals A-C showed broad-spectrum inhibitory activities on seedling growth of all plants tested (Lepidium apetalum, Raphanus sativus, Lactuca sativa, and Arabidopsis thaliana) with a dose-dependent relationship. Additionally, mucroniferals A and B exhibited significant inhibitory effects on germination of most seeds at concentration of 80 μg/mL, and the inhibition was reversible.

Co-regulation Role of Endogenous Hormones and Transcriptomics Profiling Under Cold Stress in Tetrastigma hemsleyanum

Tetrastigma hemsleyanum Diels et Gilg is a valuable medicinal herb. Chilling sensitivity is the major limiting factor of the artificial cultivation of the plant. Some key genes, such as ZEP and NCED genes of ABA biosynthesis, GA2ox, GA3ox, and GA20ox genes of GA biosynthesis, ACO genes of ET biosynthesis pathway were screened to be crucial in cold response. The response of ABA and ABA/GA1+3 to cold stress was prior to that of GA1+3, ZR, ABA/IAA, and ABA/ZR. The increasing changes in ABA/GA1+3 turned to a steep decline with the extension of stress time, which might be one factor contributing to cold sensitivity of T. hemsleyanum. The cold tolerance of T. hemsleyanum would be repressed by GA3 but enhanced by ABA when ABA orGA3 was used alone. Both the ABA-mediated promotion and GA-mediated repression of cold tolerance could be attenuated using a combination of the two phytohormones within 6 h. When the biosynthesis of ABA and GA were inhibited by FLU and PAC, respectively, the effects of GA and ABA treatment were reversed partially. In summary, we presented the first study of global hormone-regulated transcripts expression patterns in T. hemsleyanum. This study suggested that GA and ABA could work antagonistically to balance the cold stress responses. PAC, a GA biogenesis inhibitor, as well as exogenous ABA, might be potential plant growth regulators that can promote cold tolerance of T. hemsleyanum. The study also provided valuable hints in revealing the potential candidate genes that regulated cold tolerance of T. hemsleyanum.

P-Aminobenzoate Organic Salts as Potential Plant Growth Regulators for Tomatoes.

The discovery of environmentally friendly and inexpensive plant growth regulators (PGRs) for agronomically important crops is a necessity and must be considered a priority worldwide. This study provides the synthesis, structure determination and the biological evaluation of two binary organic salts as potential PGRs. New compounds have dual biological activity and are based on natural metabolite p-aminobenzoic acid (pABAH) and different alkanolamines. Studied compounds exhibit hydrogen-bonded 3D supramolecular architectures with different crystal packing due to the formation of one homosynthon and various heterosynthons. The biological profile of new compounds was investigated in laboratory and greenhouse on Solanum lycopersicum L., revealing the efficiency in promoting plant rooting and plant productivity. The results may have a positive impact on agricultural economics, developing new sustainable PGRs for tomatoes.

Effects of uniconazole with or without micronutrient on the lignin biosynthesis, lodging resistance, and winter wheat production in semiarid regions

Lodging stress results in grain yield and quality reduction in wheat. Uniconazole, a potential plant growth regulator significantly enhances lignin biosynthesis and thus provides mechanical strength to plants in order to cope with lodging stress. A field study was conducted during the 2015–2016 and 2016–2017 growing seasons, to investigate the effects of uniconazole sole application or with micronutrient on the lignin biosynthesis, lodging resistance, and production of winter wheat. In the first experiment, uniconazole at concentrations of 0 (CK), 15 (US1), 30 (US2), and 45 (US3) mg L−1 was applied as sole seed soaking, while in the second experiment with manganese (Mn) at concentration of 0.06 g L−1 Mn, 0.06 g L−1 Mn+ 15 mg L−1 uniconazole (UMS1), 0.06 g L−1 Mn+30 mg L−1 uniconazole (UMS2), and 0.06 g L−1 Mn+45 mg L−1 uniconazole (UMS3), respectively. Uniconazole sole application or with micronutrient significantly increased the lignin content by improving the lignin-related enzyme activities of phenylalanine ammonia-lyase, cinnamyl alcohol dehydrogenase, tyrosine ammonia-lyase, and peroxidase, ameliorating basal internode characteristics, and breaking strength. The spike length, spike diameter, spikes/plant, weight/spike, yield/spike, and grain yield increased and then decreased with uniconazole application at a higher concentration, where their maximum values were recorded with UMS2 and US2 treatments. The lignin accumulation was positively correlated with lignin-related enzyme activities and breaking strength while, negatively correlated with lodging rate. Uniconazole significantly improved the lignin biosynthesis, lodging resistance, and grain yield of winter wheat and the treatments which showed the greatest effects were uniconazole seed soaking with micronutrient at a concentration of 30 mg L−1 and 0.06 g L−1, and uniconazole sole seed soaking at a concentration of 30 mg L−1.

New aromatic 6-substituted 2′-deoxy-9-(β)-d-ribofuranosylpurine derivatives as potential plant growth regulators

Cytokinins are naturally occurring substances that act as plant growth regulators promoting plant growth and development, including shoot initiation and branching, and also affecting apical dominance and leaf senescence. Aromatic cytokinin 6-benzylaminopurine (BAP) has been widely used in micropropagation systems and biotechnology. However, its 9-glucoside (BAP9G) accumulates in explants, causing root inhibition and growth heterogenity. To overcome BAP disadvantages, a series of ring-substituted 2′-deoxy-9-(β)-d-ribofuranosylpurine derivatives was prepared and examined in different classical cytokinin bioassays. Amaranthus, senescence and tobacco callus bioassays were employed to provide details of cytokinin activity of 2′-deoxy-9-(β)-d-ribosides compared to their respective free bases and ribosides. The prepared derivatives were also tested for their recognition by cytokinin receptors of Arabidopsis thaliana AHK3 and CRE1/AHK4. The ability of aromatic N6-substituted adenine-2′-deoxy-9-(β)-d-ribosides to promote plant growth and delay senescence was increased considerably and, in contrast to BAP, no loss of cytokinin activity at higher concentrations was observed. The presence of a 2′-deoxyribosyl moiety at the N9-position led to an increase in cytokinin activities in comparison to the free bases and ribosides. The antioxidant capacity, cytotoxicity and effect on the MHV-68 gammaherpesvirus strain were also examined.

Phytotoxic Diterpenoids from Plants and Microorganisms.

Phytotoxic natural products with either unique or various structures are one of the most abundant sources for the discovery of potential allelochemicals, natural herbicides, and plant growth regulators. Phytotoxic diterpenoids, a relatively large class of natural products, play an important role in the plant-plant or plant-microorganism interactions. This article argues that the phytotoxic diterpenoids isolated from the plants and microorganisms can either inhibit the seed germination and the growth of plant seedlings or lead to some disease symptoms on the tested plant tissues and plant seedlings.

Synthesis and plant growth regulatory activities of 2',3'-PhABA and iso-2',3'-PhABA esters.

Methyl and phenyl esters of 2',3'-PhABA and iso-2',3'-PhABA were prepared for the biological investigation and development of practical applications. These esters exhibited excellent activity in most plant growth inhibitory assays. And, three esters were more efficient than ABA in stomatal closure. The 2',3'-PhABA analogs and their methyl esters have good stability in hydrolysis assay, and the different lipid solubility and permeability of different esters may be one of the origins of their active selectivity for different plants and physiological processes. Furthermore, in the study of drought tolerance, all four esters had comparable activity to ABA. These results suggest that these esters were potent plant growth regulator (PGR) candidates for anti-drought. The finding that different esters have different selective bioactivity and biophysical properties indicates that these esters not only function as ABA-like PGRs but also have the possibility as potential selective pro-hormone. 2',3'-BenzoABA esters as PGR candidates with prolonged and selective bioactivity.