Stimulated Root Growth Research Articles

Production of indole acetic acid by Pseudomonas sp.: effect of coinoculation with Mesorhizobium sp. Cicer on nodulation and plant growth of chickpea (Cicer arietinum)

Pseudomonas isolates obtained from the rhizosphere of chickpea (Cicer arietinum L.) and green gram (Vigna radiata) were found to produce significant amount of indole acetic acid (IAA) when grown in a LB medium broth supplemented with L-tryptophan. Seed bacterization of chickpea cultivar C235 with different Pseudomonas isolates showed stunting effect on the development of root and shoot at 5 and 10days of seedling growth except the strains MPS79 and MPS90 that showed stimulation of root growth, and strains MPS104 and MRS13 that showed shoot growth stimulation at 10days. Exogenous treatment of seeds with IAA at 0.5 and 1.0μM concentration caused similar stunting effects on root and shoot growth compared to untreated control both at 5 and 10days of observation, whereas higher concentration of IAA (10.0μM) inhibited the growth of seedlings. Coinoculation of chickpea with IAA-producing Pseudomonas strains increased nodule number and nodule biomass by Mesorhizobium sp. Cicer strain Ca181. The plant dry weights of coinoculated treatments showed 1.10 to 1.28 times increase in comparison to Mesorhizobium-inoculated plants alone and 3.62 to 4.50 times over uninoculated controls at 100days of plant growth. The results indicated the potential usefulness of allelopathic rhizosphere bacteria and growth-mediating IAA in enhancement of nodulation and stimulation of plant growth in chickpea.

Arabidopsis and Lobelia anceps access small peptides as a nitrogen source for growth.

While importance of amino acids as a nitrogen source for plants is increasingly recognised, other organic N sources including small peptides have received less attention. We assessed the capacity of functionally different species, annual and nonmycorrhizal Arabidopsis thaliana (L.) Heynh. (Brassicaceae) and perennial Lobelia anceps L.f. (Campanulaceae), to acquire, metabolise and use small peptides as a N source independent of symbionts. Plants were grown axenically on media supplemented with small peptides (2-4 amino acids), amino acids or inorganic N. In A. thaliana, peptides of up to four amino acid residues sustained growth and supported up to 74% of the maximum biomass accumulation achieved with inorganic N. Peptides also supported growth of L. anceps, but to a lesser extent. Using metabolite analysis, a proportion of the peptides supplied in the medium were detected intact in root and shoot tissue together with their metabolic products. Nitrogen source preferences, growth responses and shoot-root biomass allocation were species-specific and suggest caution in the use of Arabidopsis as the sole plant model. In particular, glycine peptides of increasing length induced effects ranging from complete inhibition to marked stimulation of root growth. This study contributes to emerging evidence that plants can acquire and metabolise organic N beyond amino acids.

Fungal lipochitooligosaccharide symbiotic signals in arbuscular mycorrhiza

Arbuscular mycorrhiza (AM) is a root endosymbiosis between plants and glomeromycete fungi. It is the most widespread terrestrial plant symbiosis, improving plant uptake of water and mineral nutrients. Yet, despite its crucial role in land ecosystems, molecular mechanisms leading to its formation are just beginning to be unravelled. Recent evidence suggests that AM fungi produce diffusible symbiotic signals. Here we show that Glomus intraradices secretes symbiotic signals that are a mixture of sulphated and non-sulphated simple lipochitooligosaccharides (LCOs), which stimulate formation of AM in plant species of diverse families (Fabaceae, Asteraceae and Umbelliferae). In the legume Medicago truncatula these signals stimulate root growth and branching by the symbiotic DMI signalling pathway. These findings provide a better understanding of the evolution of signalling mechanisms involved in plant root endosymbioses and will greatly facilitate their molecular dissection. They also open the way to using these natural and very active molecules in agriculture.

Al toxicity leads to enhanced cell division and changed photosynthesis in Oryza rufipogon L.

Oryza rufipogon L. (O. rufipogon) or a common wild rice, showed considerable aluminum (Al) tolerance. In this study, we examined the physiologic and genetic response of wild rice short term and long term to Al toxicity, respectively. In the short term study, morin staining, DAPI staining and aniline blue staining were used to detect Al distribution, cell division and callose production in the roots of O. rufipogon. The results indicated cell division could be enhanced by Al within low concentration range. In the long term study, we chose Oryza sativa L (O. sativa) (the close sib of O. rufipogon) as a reference. It showed that O. rufipogon grew better than O. sativa when treated with Al of 1.4 mmol/l concentration and also experienced a short period of root growth stimulation. This study gave some basic data to explain the mechanisms Oryza rufipogon L. developed to deal with Al and lay a good foundation to further study. SSH (suppression subtractive hybridization) proved that transcripts of the small subunit of Rubisco and a Photosystem I P700 apoprotein were enhanced under long term Al treatment in wild rice. Further investigation via the assessment of the content of chlorophyll a, b indicated that the content of chlorophyll a, b in the leaves of O. rufipogon generally rose after Al treatment for 15 days. This indicated that intake of Al can affect photosynthesis of plant.

UJI ANTIBAKTERI Lasianthus (RUBIACEAE) SEBAGAI TUMBUHAN BERKHASIAT OBAT DAN UPAYA PERBANYAKANNYA

Lasianthus, a member of the family Rubiaceae has potential for medicinal plants. The aims of the research were to find out the potential antibacterial activity of Lasianthus leaf extract and to investigate the effectiveness of plant propagation by stems cutting. The species tested were Lasianthus laevigatus Blume, L furcatus (Miq.) Bremek and L. cf. obscurus Blume. The extracted leaves in n-hexana, ethyl acetate and methanol were tested in vitro against Staphylococcus aureus and Escherichia coil activities that grown on medium of Mueller-Hinton agar. The methanol extracts of each plant material showed significant antibacterial activities on S. aureus and E. coll. Antibacterial activity increased with increasing concentration of the extracts. Plant propagation by stems cutting were done as a first step of conservation effort for respective species. Stems cutting of L. laevigatus, L. purpureus, L. furcatus, L. acuminatus, L rhinocerotis. and L. cf. obscurus with length of 10 cm were applied with Rotoon F to stimulate root growth. The result of plant propagation research showed that only the stems cutting of L. cf. obscurus grew well although roots did not grow until 4 months.

Pioneering works in biochar research, Japan

In Asian countries, people have a long history of using rice husk charcoal or wood ash as an agricultural soil amendment, but evidence of this has been long obscured. Since the 1980s, microbiological studies, mainly on symbiotic organisms, have been performed in Japan. Charcoal is a porous material with high water and air retention capacities and high alkalinity. Therefore, it stimulates root growth and enhances the infection of various symbiotic microbes to plant partners. The use of carbonised materials in agriculture, forestry, and construction will contribute to the sustainability of crop production, soil conservation, and carbon sequestration. Biochar-related research accumulated mainly in Japan is reviewed.

Distribuição de massa molecular de ácidos húmicos e promoção do crescimento radicular

Os ácidos húmicos (AH) estimulam diretamente vários processos fisiológicos que promovem o crescimento vegetal, especialmente do sistema radicular. O conhecimento da natureza química e do papel de AH na expressão de efeitos biofertilizantes e bioestimulantes é fundamental para o desenvolvimento de insumos biológicos à base de ácidos húmicos. O objetivo deste trabalho foi avaliar uma possível relação entre a distribuição de massa molecular aparente de AH isolados de vermicomposto e a magnitude de resposta na promoção do crescimento radicular. Para isso, foram obtidas subfrações (SF) dos AH por meio de cromatografia preparativa por exclusão de tamanho em gel de Sephadex G-50 (CGE). O processo preparativo foi validado pelo uso da cromatografia líquida de alta performance por exclusão de tamanho (HPSEC). As cinco frações obtidas foram testadas em diferentes concentrações (0; 0,0001; 0,001; 0,003; 0,005; e 0,01 mol L-1 de C) quanto à sua capacidade de estimular o crescimento radicular de plantas de Arabidopsis thaliana (ecótipo col. 4). Para plantas de milho (Zea mays hyb. UENF 506-6) foi utilizada a dose de 0,002 mol L-1 de C. O modelo quadrático descreveu a indução do crescimento radicular de Arabidopsis e a dose de AH, sendo 0,00511 mol L-1 de C o ponto de inflexão médio. Na concentração ótima, foi observada correlação inversa e significativa entre distribuição de massa molecular e indução do número de raízes laterais em Arabidopsis. No entanto, outros atributos, como área e comprimento radicular, não sofreram influência da massa molecular aparente. Em plântulas de milho, foi observado aumento no número de sítios de mitose e raízes laterais tanto no tratamento com AH como com suas subfrações. A atividade da H+-ATPase de membrana plasmática foi significativamente alterada pelo AH, porém não ocorreu o mesmo com todas as subfrações. A atividade de estimulação do crescimento radicular parece estar mais relacionada com a estrutura química das substâncias húmicas do que com a distribuição de massa molecular dos agregados húmicos.

The impact of supplemental carbon sources on Arabidopsis thaliana growth, chlorophyll content and anthocyanin accumulation

This research explores the impacts of a broad range of supplemental carbon sources on growth and development of Arabidopsis thaliana. Parameters measured include dark-germinated hypocotyl length, light-germinated root growth, rosette growth, chlorophyll concentration and anthocyanin content. Treatment sugars include sucrose, maltose, d-glucose, d-fructose, l-arabinose, l-fucose, d-galactose, d-mannose, l-rhamnose and d-xylose each supplied at 4, 20 or 100 mM. This comparison of the effect of different carbon sources on multiple parameters and under identical conditions showed that every carbon source had unique qualitative and quantitative effects on Arabidopsis growth and development. Root growth was particularly sensitive to supplemental carbon source. Growth on 100 mM sucrose, maltose, glucose or xylose stimulated root growth by ~100%. Growth on arabinose, fucose, galactose, mannose or rhamnose inhibited root growth by 50% or more. Several sugars that strongly inhibited root growth had either no effect (galactose and fucose) or a positive effect (arabinose) on hypocotyl elongation and rosette growth. Rhamnose was the only carbon source that inhibited hypocotyl elongation across all concentrations. Sucrose, maltose, glucose, fructose, arabinose or xylose stimulated rosette growth by ~50%. Chlorophyll content was strongly reduced by mannose while sucrose, glucose, galactose and rhamnose caused smaller reductions. Anthocyanin accumulation was strongly induced by both galactose and mannose. Only mannose impacted all parameters across all concentrations. Based on these data it can be concluded that the effect of each carbon source on Arabidopsis growth and development is specific in terms of both magnitude and the parameters impacted.

Plant-Growth-Promoting Rhizobacteria

Several microbes promote plant growth, and many microbial products that stimulate plant growth have been marketed. In this review we restrict ourselves to bacteria that are derived from and exert this effect on the root. Such bacteria are generally designated as PGPR (plant-growth-promoting rhizobacteria). The beneficial effects of these rhizobacteria on plant growth can be direct or indirect. This review begins with describing the conditions under which bacteria live in the rhizosphere. To exert their beneficial effects, bacteria usually must colonize the root surface efficiently. Therefore, bacterial traits required for root colonization are subsequently described. Finally, several mechanisms by which microbes can act beneficially on plant growth are described. Examples of direct plant growth promotion that are discussed include (a) biofertilization, (b) stimulation of root growth, (c) rhizoremediation, and (d) plant stress control. Mechanisms of biological control by which rhizobacteria can promote plant growth indirectly, i.e., by reducing the level of disease, include antibiosis, induction of systemic resistance, and competition for nutrients and niches.

USE OF PLANT WATER POTENTIAL FOR SCHEDULING IRRIGATION OF ANATOLIAN BLACK PINE (Pinus nigra Arn. subsp. pallasiana (Lamb.) Holmboe) SEEDLINGS

The aim of this study was to set up an irrigation scheduling for bare-root Anatolian black pine seedlings growing in the Egirdir Forest Nursery using plant water potential as an indicator of plant water stress. For this purpose, predawn, midday and daily plant water potentials were measured periodically with plant pressure chamber from mid April till mid November in second growing season of Anatolian black pine seedlings. According to the results, irrigations in the nursery should start in mid April and continue until early June and should be applied when predawn water potential drops below -0.5 MPa. After this period in the phase of bud dormancy initiation (early June till early September), to stimulate root growth and extension only when predawn water potential drops -0.8 MPa, seedlings should be adjusted to bring the top 20 cm of the soil to field capacity. In the last period (early September-mid November) watering should commence when predawn water potential drops below -1.3 MPa. Plant water potential should not be allowed to fall below -1.3 MPa during the day. Keyword: Anatolian black pine, predawn water potential, irrigation scheduling

Nitrate leaching stimulates subsurface root growth of wheat and increases rhizosphere alkalisation in a highly acidic soil

Subsurface acidity is a major factor limiting crop yield in some agricultural soils. The surface application of lime has limited effect on the subsurface acidity due to the slow downward movement, while deep incorporation of lime is costly. This paper tested the concept of biologically ameliorating subsurface acidity in a highly acidic soil through the net uptake of anions by plant roots. Nitrogen was supplied to the top soil (0–10 cm) as Ca(NO3)2 at rates equivalent to 30–240 kg N ha−1. Four water levels were imposed (40, 60, 80 and 100% of field capacity). Aluminium-tolerant wheat was grown for 58 days. The high N and high water treatments stimulated root growth below 15 cm, which in turn increased N capture, resulting in a greater excess anion uptake over cations and thus alkalisation of subsurface soil layers. This study suggests that it is feasible to exploit the process of nitrate uptake by an aluminium-tolerant wheat genotype to increase pH in acidic subsoil.

Cichoric acid production from hairy root cultures of Echinacea purpurea grown in a modified airlift bioreactor

AbstractBACKGROUND: Hairy root cultures of Echinacea offer great potential for the production of valuable cichoric acid, but scale‐up of the culture in the bioreactor represents a big challenge. Therefore, there is great interest in developing a suitable bioreactor for hairy root culture of Echinacea and novel bioprocessing strategies for intensifying cichoric acid production.RESULTS: Homogenous distribution of inoculum roots and high cichoric acid production were observed in a bioreactor modified by installing a mesh draught tube with an average pore size 700 µm, slightly larger than the hairy root, about 500 µm. Improved root growth and cichoric acid production were improved by increasing the aeration rate from 0.002 m3 h−1 to 0.012 m3 h−1. The hairy root cultures in the modified bioreactor exposed once to 6 min of ultrasound treatment at day 20 gave the highest biomass accumulation of 12.8 ± 0.3 g L−1, which resulted in the maximum cichoric acid production of 178.2 ± 4.9 mg L−1 at day 30.CONCLUSION: The present work demonstrated the effectiveness of hairy root culture in a modified airlift bioreactor. The biomass distribution remained homogenous in the modified airlift bioreactor, and the cichoric acid production was improved owing to the even root growth at optimal air flow rate. An interesting finding of this investigation was that ultrasound stimulated root growth and cichoric acid production considerably in the modified airlift bioreactor. Copyright © 2009 Society of Chemical Industry

Creeping Bentgrass Putting Green Turf Responses to Two Summer Irrigation Practices: Rooting and Soil Temperature

Light and frequent (LF) and deep and infrequent (DI) irrigation are two common practices for golf course managers. Few studies have compared the effects of these two opposing irrigation practices on summer root performance in creeping bentgrass (Agrostis stolonifera L.). The objectives of this field study were to quantify summer root development and longevity in response to LF vs. DI irrigation in ‘Providence’ creeping bentgrass grown on a sand‐based rootzone. The LF plots were irrigated daily to moisten the upper 4 to 6 cm of soil, whereas DI plots were irrigated at leaf wilt to wet soil to a depth ≥24 cm. Root measurements were obtained using the minirhizotron imaging technique and included total root count, total root length (TRL), total root surface area (TRSA), and average root diameter. When averaged over the entire 0‐ to 24‐cm rootzone depth, DI‐irrigated creeping bentgrass produced a greater number of roots, longer root lengths, and a larger root surface area than LF‐irrigated turf. Average root diameters were smaller in DI‐irrigated creeping bentgrass in the summer of 2007. Compared with data collected in 2006, the 2‐yr‐old turf had 55 and 32% fewer roots in LF‐ and DI‐irrigated bentgrass by September 2007, respectively. There were similar reductions in TRL and TRSA between years in both irrigation regimes. Deep and infrequent irrigation stimulated root growth throughout the 0‐ to 24‐cm rootzone in May and June and promoted root longevity in summer.

Terrestrial carbon‐cycle feedback to climate warming: experimental evidence on plant regulation and impacts of biofuel feedstock harvest

AbstractFeedback between global carbon (C) cycles and climate change is one of the major uncertainties in projecting future global warming. Coupled carbon–climate models all demonstrated a positive feedback between terrestrial C cycle and climate warming. The positive feedback results from decreased net primary production (NPP) in most models and increased respiratory C release by all the models under climate warming. Those modeling results present interesting hypotheses of future states of ecosystems and climate, which are yet to be tested against experimental results. In this study, we examined ecosystem C balance and its major components in a warming and clipping experiment in a North America tallgrass prairie. Infrared heaters have been used to elevate soil temperature by approximately 2 °C continuously since November 1999. Clipping once a year was to mimic hay or biofuel feedstock harvest. On average of data over 6 years from 2000 to 2005, estimated NPP under warming increased by 14% without clipping (P<0.05) and 26% with clipping (P<0.05) in comparison with that under control. Warming did not result in instantaneous increases in soil respiration in 1999 and 2000 but significantly increased it by approximately 8% without clipping (P<0.05) from 2001 to 2005. Soil respiration under warming increased by 15% with clipping (P<0.05) from 2000 to 2005. Warming‐stimulated plant biomass production, due to enhanced C4 dominance, extended growing seasons, and increased nitrogen uptake and use efficiency, offset increased soil respiration, leading to no change in soil C storage at our site. However, biofuel feedstock harvest by biomass removal resulted in significant soil C loss in the clipping and control plots but was carbon negative in the clipping and warming plots largely because of positive interactions of warming and clipping in stimulating root growth. Our results demonstrate that plant production processes play a critical role in regulation of ecosystem carbon‐cycle feedback to climate change in both the current ambient and future warmed world.

Terrestrial carbon-cycle feedback to climate warming: experimental evidence on plant regulation and impacts of biofuel feedstock harvest

Feedback between global carbon (C) cycles and climate change is one of the major uncertainties in projecting future global warming. Coupled carbon–climate models all demonstrated a positive feedback between terrestrial C cycle and climate warming. The positive feedback results from decreased net primary production (NPP) in most models and increased respiratory C release by all the models under climate warming. Those modeling results present interesting hypotheses of future states of ecosystems and climate, which are yet to be tested against experimental results. In this study, we examined ecosystem C balance and its major components in a warming and clipping experiment in a North America tallgrass prairie. Infrared heaters have been used to elevate soil temperature by approximately 21C continuously since November 1999. Clipping once a year was to mimic hay or biofuel feedstock harvest. On average of data over 6 years from 2000 to 2005, estimated NPP under warming increased by 14% without clipping (Po0.05) and 26% with clipping (Po0.05) in comparison with that under control. Warming did not result in instantaneous increases in soil respiration in 1999 and 2000 but significantly increased it by approximately 8% without clipping (Po0.05) from 2001 to 2005. Soil respiration under warming increased by 15% with clipping (Po0.05) from 2000 to 2005. Warming-stimulated plant biomass production, due to enhanced C4 dominance, extended growing seasons, and increased nitrogen uptake and use efficiency, offset increased soil respiration, leading to no change in soil C storage at our site. However, biofuel feedstock harvest by biomass removal resulted in significant soil C loss in the clipping and control plots but was carbon negative in the clipping and warming plots largely because of positive interactions of warming and clipping in stimulating root growth. Our results demonstrate that plant production processes play a critical role in regulation of ecosystem carbon-cycle feedback to climate change in both the current ambient and future warmed world.

Effect of Cyclanilide on Auxin Activity

Cyclanilide is a plant growth regulator that is registered for use in cotton at different stages of growth, to either suppress vegetative growth (in combination with mepiquat chloride) or accelerate senescence (enhance defoliation and boll opening, used in combination with ethephon). This research was conducted to study the mechanism of action of cyclanilide: its potential interaction with auxin (IAA) transport and signaling in plants. The activity of cyclanilide was compared with the activity of the auxin transport inhibitors NPA and TIBA. Movement of [3H]IAA was inhibited in etiolated corn coleoptiles by 10 μM cyclanilide, NPA, and TIBA, which demonstrated that cyclanilide affected polar auxin transport. Although NPA inhibited [3H]IAA efflux from cells in etiolated zucchini hypocotyls, cyclanilide had no effect. NPA did not inhibit the influx of IAA into cells in etiolated zucchini hypocotyls, whereas cyclanilide inhibited uptake 25 and 31% at 10 and 100 μM, respectively. Also, NPA inhibited the gravitropic response in tomato roots (85% at 1 μM) more than cyclanilide (30% at 1 μM). Although NPA inhibited tomato root growth (30% at 1 μM), cyclanilide stimulated root growth (165% of control at 5 μM). To further characterize cyclanilide action, plasma membrane fractions from etiolated zucchini hypocotyls were obtained and the binding of NPA, IAA, and cyclanilide studied. Cyclanilide inhibited the binding of [3H]NPA and [3H]IAA with an IC50 of 50 μM for both. NPA did not affect the binding of IAA, nor did IAA affect the binding of NPA. Kinetic analysis indicated that cyclanilide is a noncompetitive inhibitor of both NPA and IAA binding, with inhibition constants (K i) of 40 and 2.3 μM, respectively. These data demonstrated that cyclanilide interacts with auxin-regulated processes via a mechanism that is distinct from other auxin transport inhibitors. This research identifies a possible mechanism of action for cyclanilide when used as a plant growth regulator.

Exogenously applied melatonin stimulates root growth and raises endogenous indoleacetic acid in roots of etiolated seedlings of Brassica juncea

Exogenous melatonin was applied to etiolated seedlings of wild leaf mustard (Brassica juncea) and the effect on root growth and endogenous indole-3-acetic acid (IAA) levels determined. The results show that 0.1microM melatonin has a stimulatory effect on root growth, while 100microM is inhibitory. Furthermore, the stimulatory effect was only detectable in young seedlings (2-d old). Older seedlings (4-d old) appear to be less susceptible to both the stimulatory and the inhibitory effect of melatonin. Exogenous application of 0.1microM melatonin also raised the endogenous levels of free IAA in roots, while higher concentrations had no significant effect. The specific mechanism that causes exogenous melatonin to increase the amount of free IAA in roots, paired with a stimulation of root growth, remains to be uncovered.

A distinct endosomal Ca2+/Mn2+ pump affects root growth through the secretory process.

Ca(2+) is required for protein processing, sorting, and secretion in eukaryotic cells, although the particular roles of the transporters involved in the secretory system of plants are obscure. One endomembrane-type Ca-ATPase from Arabidopsis (Arabidopsis thaliana), AtECA3, diverges from AtECA1, AtECA2, and AtECA4 in protein sequence; yet, AtECA3 appears similar in transport activity to the endoplasmic reticulum (ER)-bound AtECA1. Expression of AtECA3 in a yeast (Saccharomyces cerevisiae) mutant defective in its endogenous Ca(2+) pumps conferred the ability to grow on Ca(2+)-depleted medium and tolerance to toxic levels of Mn(2+). A green fluorescent protein-tagged AtECA3 was functionally competent and localized to intracellular membranes of yeast, suggesting that Ca(2+) and Mn(2+) loading into internal compartment(s) enhanced yeast proliferation. In mesophyll protoplasts, AtECA3-green fluorescent protein associated with a subpopulation of endosome/prevacuolar compartments based on partial colocalization with the Ara7 marker. Interestingly, three independent eca3 T-DNA disruption mutants showed severe reduction in root growth normally stimulated by 3 mm Ca(2+), indicating that AtECA3 function cannot be replaced by an ER-associated AtECA1. Furthermore, root growth of mutants is sensitive to 50 microm Mn(2+), indicating that AtECA3 is also important for the detoxification of excess Mn(2+). Curiously, Ateca3 mutant roots produced 65% more apoplastic protein than wild-type roots, as monitored by peroxidase activity, suggesting that the secretory process was altered. Together, these results demonstrate that the role of AtECA3 is distinct from that of the more abundant ER AtECA1. AtECA3 supports Ca(2+)-stimulated root growth and the detoxification of high Mn(2+), possibly through activities mediated by post-Golgi compartments that coordinate membrane traffic and sorting of materials to the vacuole and the cell wall.

MANIPULATION OF SOIL: PLANT SIGNALLING NETWORKS TO LIMIT WATER USE AND SUSTAIN PLANT PRODUCTIVITY DURING DEFICIT IRRIGATION – A REVIEW

ISHS V International Symposium on Irrigation of Horticultural Crops MANIPULATION OF SOIL: PLANT SIGNALLING NETWORKS TO LIMIT WATER USE AND SUSTAIN PLANT PRODUCTIVITY DURING DEFICIT IRRIGATION – A REVIEW

Identification of auxins by a chemical genomics approach.

Thirteen auxenic compounds were discovered in a screen of 10 000 compounds for auxin-like activity in Arabidopsis roots. One of the most potent substances was 2-(4-chloro-2-methylphenoxy)-N-(4-H-1,2,4-triazol-3-yl)acetamide (WH7) which shares similar structure to the known auxenic herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). A selected set of 20 analogues of WH7 was used to provide detailed information about the structure–activity relationship based on their efficacy at inhibiting and stimulating root and shoot growth, respectively, and at induction of gene expression. It was shown that WH7 acts in a genetically defined auxin pathway. These small molecules will extend the arsenal of substances that can be used to define auxin perception site(s) and to dissect subsequent signalling events.