Auxin Research Papers - Academia.edu (original) (raw)

Callus induction from petiole explants has been achieved in Alocasia micholitziana `Green Velvet'. The highest percentage (71%) of explants inducing callus was obtained on MS medium supplemented with 0.5 μM 2,4-D and 0.5 μM kinetin in the dark after 4 months of culture. Shoots were regenerated at the highest frequency of 33.3% under light condition when 0.5 μM BA was added to MS medium with the average of 7.8±2.3 shoots per callus explant. The callus-derived shoots rooted on hormone free MS medium and within 4 weeks the plantlets were ready for acclimatization. The regenerated plants appeared morphologically similar to mother plants.

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- Genetics, Regeneration, Plant Biology, Tissue culture

Plants deploy a finely tuned balance between growth and defence responses for better fitness. Crosstalk between defence signalling hormones such as salicylic acid (SA) and jasmonates (JAs) as well as growth regulators plays a significant role in mediating the trade-off between growth and defence in plants. Here, we specifically discuss how the mutual antagonism between the signalling of auxin and SA impacts on plant growth and defence. Furthermore, the synergism between auxin and JA benefits a class of plant pathogens. JA signalling also poses growth cuts through auxin. We discuss how the effect of cytokinins (CKs) is multifaceted and is effective against a broad range of pathogens in mediating immunity. The synergism between CKs and SA promotes defence against biotrophs. Reciprocally, SA inhibits CK-mediated growth responses. Recent reports show that CKs promote JA responses; however, in a feedback loop, JA suppresses CK responses. We also highlight crosstalk between auxin and CKs ...

- by Muhammad Naseem
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- Plant Biology, Biology, Cell Biology, Medicine

... Hydrolases Alters Substrate Specificity James J. Campanella & Scott Sigethy & Jutta Ludwig-Müller ... J Biol Chem 277:2044620452 Ludwig-Müller J, Epstein E, Hilgenberg W (1996) Auxin-conjugate hydrolysis in Chinese cabbage:... more

- by James Campanella
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- Plant Biology, Plant Molecular Biology, Auxin, Amino Acid Profile

Fully habituated organogenic and nonorganogenic sugarbeet calluses reacted to application of the synthetic auxin [3-benzo(b) selenienyl] acetic acid by changes in growth and ethylene production. Treatment of fully habituated cells of periwinkle with 2,4-dichlorophenoxyacetic acid led to the decrease of free cytokinin contents (isopentenyl adenine, zeatin riboside, and zeatin) during the late exponential phase of growth. The polyamine contents were also modified and the capacity to biotransform secologanin into ajmalicine was decreased. Treatment of the habituated periwinkle cells with zeatin greatly increased the amount of a polypeptide of 16 kDa; this response was more marked than that displayed by the auxin-dependent line. These data show that hormone-independent calluses and cell suspensions can retain some sensitivity to growth hormones. However, differences of responses were observed between the auxin-dependent lines and the habituated lines.

- by Mohammed Filali
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- Plant Biology, Growth Hormone, Auxin, Plant Growth Regulator

We compared the kinetics of auxin redistribution across the caps of primary roots of 2-day-old maize (Zea mays, cv Merit) seedlings with the time course of gravitropic curvature. [3H] indoleacetic acid was applied to one side of the cap in an agar donor and radioactivity moving across the cap was collected in an agar receiver applied to the opposite side. Upon gravistimulation the roots first curved upward slightly, then retumed to the horizontal and began curving downward, reaching a final angle

- by Linda Young
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- Kinetics, Biological Sciences, Plant Physiology, Plant Growth Regulators

Increasing evidences have indicated that humic substances can induce plant growth and productivity by functioning as an environmental source of auxinic activity. Here we comparatively evaluate the effects of indole-3-acetic acid (IAA) and humic acids (HA) isolated from two different soils (Inseptsol and Ultisol) and two different organic residues (vermicompost and sewage sludge) on root development and on activities of plasmalemma and tonoplast H+ pumps from maize roots. The data show that HA isolated from these different sources as well as low IAA concentrations (10−10 and 10−15 M) improve root growth through a markedly proliferation of lateral roots along with a differential activation not only of the plasmalemma but also of vacuolar H+-ATPases and H+-pyrophosphatase. Further, the vacuolar H+-ATPase had a peak of stimulation in a range from 10−8 to 10−10 M IAA, whereas the H+-pyrophosphatase was sensitive to a much broader range of IAA concentrations from 10−3 to 10−15 M. It is proposed a complementary view of the acid growth mechanism in which a concerted activation of the plasmalemma and tonoplast H+ pumps plays a key role in the root cell expansion process driven by environment-derived molecules endowed with auxinic activity, such as that of humic substances.

- by Daniel Zandonadi
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- Plant Biology, Sewage sludge, Maize, Plant growth

In Arabidopsis thaliana, the carotenoid cleavage dioxygenases (CCDs) MAX3 and MAX4 act together with MAX1 to produce a strigolactone signalling molecule required for the inhibition of axillary bud outgrowth. We show that both MAX3 and MAX4 transcripts are positively auxin regulated in a manner similar to the orthologous genes from pea (Pisum sativum) and rice (Oryza sativa), supporting evolutionary conservation of this regulation in plants. This regulation is important for branching control because large auxin-related reductions in these transcripts are associated with increased axillary branching. Both transcripts are up-regulated in max mutants, and consistent with max mutants having increased auxin in the polar auxin transport stream (PATS), this feedback regulation involves auxin signalling. We suggest that both auxin and strigolactone have the capacity to modulate each other's levels and distribution in a dynamic feedback loop required for the co-ordinated control of axillary branching.

- by Alice Hayward and +1
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- Signal Transduction, Biological Sciences, Plant Physiology, Arabidopsis

There was an apparent difference in tissue origin of adventitious roots in stem cuttings collected from Dracaena and Cordyline. Dracaena was difficulty rooting but Cordyline root quickly and easily when cuttings are taken from stock plants. The reasons for this could be due to their anatomy. The difficult-to-root cutting in Dracaena related to the presence of sclerenchyma ring between phloem and cortex. So Dracaena cutting require the application of auxin that has effects on the anatomical events that associated with the rooting process. The ease-to-root cutting Cordyline occurs as a result of the presence of preformed initials form within the cutting tissues that occurs readily on cutting without the need for special treatments of root formation. Hence, it is necessary to use anatomical study as indicator/markers of rooting ability. The application of IBA at 1000ppm proved to be the most effective treatment in stimulating adventitious root formation on Dracaena cutting; it recorded...

- by Mohamed GAD
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- Agriculture, Plant Anatomy, Plant propagation, Plant Growth Regulators

Higher plants possess a large set of the classical guaiacol peroxidases (class III peroxidases, E.C. 1.11.1.7). These enzymes have been implicated in a wide array of physiological processes such as H 2 O 2 detoxification, auxin catabolism and lignin biosynthesis and stress response (wounding, pathogen attack, etc.). During the last 10 years, molecular cloning has allowed the isolation and characterization of several genes encoding peroxidases in plants. The achievement of the large scale Arabidopsis genome sequencing, combined with the DNA complementary to RNA (cDNA) expressed sequence tags projects, provided the opportunity to draw up the first comprehensive list of peroxidases in a plant. By screening the available databases, we have identified 73 peroxidase genes throughout the Arabidopsis genome. The evolution of the peroxidase multigene family has been investigated by analyzing the gene structure (intron/exon) in correlation with the phylogenetic relationships between the isoperoxidases. An evolutionary pattern of extensive gene duplications can be inferred and is discussed. Using a cDNA array procedure, the expression pattern of 23 peroxidases was established in the different organs of the plant. All the tested peroxidases were expressed at various levels in roots, while several were also detected in stems, leaves and flowers. The specific functions of these genes remain to be determined. q

- by Hubert Greppin and +1
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- Genetics, Arabidopsis thaliana, Phylogeny, Peroxidase

Although numerous physiological studies have addressed the interactions between brassinosteroids and auxins, little is known about the underlying molecular mechanisms. Using an Affymetrix GeneChip representing approximately 8,300 Arabidopsis genes, we studied comprehensive transcript profiles over 24 h in response to indole-3-acetic acid (IAA) and brassinolide (BL). We identified 409 genes as BL inducible, 276 genes as IAA inducible, and 637 genes in total. These two hormones regulated only 48 genes in common, suggesting that most of the actions of each hormone are mediated by gene expression that is unique to each. IAA-up-regulated genes were enriched in genes regulated in common. They were induced quickly by IAA and more slowly by BL, suggesting divergent physiological roles. Many were early auxin-inducible genes and their homologs, namely SAUR, GH3, and IAA. The comprehensive comparison also identified IAA-and BL-specific genes, which should help to elucidate the specific actions of each hormone. The identified genes were classified using hierarchical clustering based on the similarity of their responses to the two hormones. Gene classification also allowed us to analyze the frequency of cis-elements. The TGTCTC element, a core element of the previously reported auxin response element, was not enriched in genes specifically regulated by IAA but was enriched in the 59-flanking region of genes up-regulated by both IAA and BL. Such gene classification should be useful for predicting the functions of unknown genes, to understand the roles of these two hormones, and the promoter analysis should provide insight into the interaction of transcriptional regulation by the two hormones. fax 81-45-503-9492.

- by Shigeo Yoshida
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- Signal Transduction, Biological Sciences, Phylogeny, Plant Physiology
- by Sairam Rudrabhatla
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- Plant Biology, Biology, Soybean, Explant Culture

Polar transport of the phytohormone auxin mediates various processes in plant growth and development, such as apical dominance, tropisms, vascular patterning and axis formation. This view is based largely on the effects of polar auxin transport inhibitors. These compounds disrupt auxin efflux from the cell but their mode of action is unknown. It is thought that polar auxin flux is caused by the asymmetric distribution of efflux carriers acting at the plasma membrane. The polar localization of efflux carrier candidate PIN1 supports this model. Here we show that the seemingly static localization of PIN1 results from rapid actin-dependent cycling between the plasma membrane and endosomal compartments. Auxin transport inhibitors block PIN1 cycling and inhibit trafficking of membrane proteins that are unrelated to auxin transport. Our data suggest that PIN1 cycling is of central importance for auxin transport and that auxin transport inhibitors affect efflux by generally interfering with...

- by Klaus Palme
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- Membrane Proteins, Membrane Trafficking, Multidisciplinary, Nature
- by Gloria Muday
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- Botany, Genetics, Gene expression, Arabidopsis thaliana

Since the 1930's the plant growth regulator Indole-3-butyric acid (IBA) has been used for rooting of plant cuttings and other growth processes. Thousands of articles have been written on it as the favorite single compound used to promote rooting. Uses for IBA other than rooting include promoting root regeneration when transplanting rooted plants and to improve grafting. Useful compounds containing IBA are solutions and powders. Solutions of IBA dissolved in water are useful for more purposes than any other compound.

- by Joel Kroin
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- Plant Biology, Plant Physiology (Biology), Plant biotechnology, Plant Physiology

Ananas comosus (L.) Merr. var. Smooth Cayenne plants when grown in vitro under different temperature regimes developed as CAM or as C 3 plants. The plants used in this study were developed from the lateral buds of the nodal etiolated stem explants cultured on Murashige and Skoog medium for 3 mo. The cultures were maintained under a 16-h photoperiod for different thermoperiods. With 288C light/158C dark thermoperiod, as compared with constant 288C light and dark, pineapple plants had a succulence index two times greater, and also a greater nocturnal titratable acidity and phosphoenolpyruvate carboxylase (PEPCase) activity, indicating CAM-type photosynthesis. The highest abscisic acid (ABA) level occurred during the light period, 8 h prior to maximum PEPCase activity, while the indole-3-acetic acid (IAA) peak was found during the dark period, coinciding with the time of highest PEPCase activity. These plants were also smaller with thicker leaves and fewer roots, but had greater dry weight. Their leaves showed histological characteristics of CAM plants, such as the presence of greater quantities of chlorenchyma and hypoderm. In addition, their vascular system was more conspicuous. In contrast, under constant temperature (288C light/dark) plants showed little succulence in the leaves. There was no significant acid oscillation and diurnal variation in PEPCase activity in these plants, suggesting the occurrence of C 3 photosynthesis. Also, no diurnal variation in ABA and IAA contents was observed. The results of this study clearly indicate a role for temperature in determining the type of carbon fixation pathway in in vitro grown pineapple. Evidence that ABA and IAA participate in CAM signaling is provided.

- by Jane Kraus
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- Plant Biology, Oscillations, Auxin, Diurnal Variation

Stem explants obtained from a mature tree of Ziziphus mauritiana Lamk were grown on modified Murashige and Skoog medium containing 3800 mg 1 -l potassium nitrate, 2475 mg 1 -l ammonium nitrate, 11 ~tM benzyladenine and 0.5 ~tM indole-3-acetic acid. During successive subcultures 15-20 shoots per inoculum were produced. Rooting was induced by pretreatment with 50 ~tM indolebutyric acid or 1-naphthaleneacetic acid for 24 h followed by transfer to auxin-free White's medium. Plantlets grew well in a soil and vermiculite mixture.

- by Dilip Nandwani
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- Regeneration, Plant Biology, Cell Culture, STEM

Transgenic and non transgenic Nicotiana tabacum L (cultivar Wisconsin) containing Ri T-DNA were treated with 0, 0.2 and 0.4 mgL -1 GA 3 in Murashig and Skoog medium. Some physiological parameters including shoot length, leaf area, number of auxiliary bud, fresh and dry weight, number and length of trichomes were measured. Shoot length, fresh weight and dry weight were increased but number of trichome did not change by GA 3 treatment. Chlorophyll, carotenoid and anthocyanin pigments of leaf were decreased. Auxin and gibberellic acid content of leaf and root were also measured. Exogenous GA 3 increased root auxin in the transgenic plants while it did not change in shoot. GA 3 treatment increased gibberellin content in both of root and shoot.

It was evaluated the effect of the use of CaCl2 and NAA on 'Niagara Rosada' grapes in order to reduce postharvest losses caused by rot and drop of berries. The experiments were carried out in vineyards in Jales and Louveira, State of São Paulo, Brazil, in 2005 and 2006. In 2005 the effects of five concentrations of CaCl2 (0; 5; 10; 15, and 20 g.L-1) with and without the use of 100 mg.L-1 of NAA were evaluated. Based on those results, in 2006 another experiment was carried out in which the use of four concentrations of NAA (0; 50, 100, and 150 mg.L-1), with and without the use of 10g L-1 CaCl2 were tested. The different concentrations of NAA were applied the day before harvest; meanwhile CaCl2 was applied at the beginning of the berry ripening. Right after harvest, the grapes were evaluated for total soluble solids, titratable acidity, pH, percentage of abscission post-harvest and decay incidence. The grapes of the different treatments were stored under two conditions: 25ºC/70% RH for 5 days and at 1ºC /85% RH for 21 days followed by storage at 25ºC/70% RH for 5 more days. At the end of each storage period, the grapes were evaluated for the same variables. The results indicate that application of NAA was effective in reducing the percentage of drop berries and the incidence of decay, mainly in those fruits stored at 25ºC/70% RH, being the concentration of 150 mg.L-1 the most effective. The treatments did not cause significant differences on total soluble solids, pH, and titratable acidity.

- by JuLIAnA SaNcHeS
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- Auxin, Titratable acidity

High rooting percentages and high-quality adventitious root systems for papaya (Carica papaya L.) were obtained in vitro by appropriate auxin source, duration of exposure to auxin and use of riboflavin. Root initiation of papaya shoots was higher using IBA than IAA, NAA or PCPA. Maximum rooting percentage (96%) was achieved by exposure of shoots to a medium containing 10 I~M IBA for 3 days before transfer to a hormone-free medium. However, the resultant plants had small shoots and callused roots. Shoot and root growth were improved when shoots were transferred after 2 days from medium containing 10 ~M IBA to hormone-free medium containing 10 p.M riboflavin. Good root initiation, and root and shoot growth were also obtained when shoots were incubated for 2 days in darkness on a medium containing 10 IxM IBA and 31 txM riboflavin before transfer to light. Alternatively, cultures could be placed in the light on medium containing 10 I~M IBA, and after 1 day the medium overlaid with 300 ~M riboflavin (1 ml over 10 ml of medium).

- by J. McComb
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- Plant Biology, Carica papaya, Auxin, Root System

Formation of the vascular system in plant leaves can be explained by the canalization hypothesis which states that veins are formed in an initially homogeneous field by a self-organizing process between the plant hormone auxin and auxin carrier proteins. Previous models of canalization can generate vein patterns with branching but fail to generate vein patterns with closed loops. However, closed vein loops are commonly observed in plant leaves and are important in making them robust to herbivore attacks and physical damage. Here we propose a new model which generates a vein system with closed loops. We postulate that the ''flux bifurcator'' level is enhanced in cells with a high auxin flux and that it causes reallocation of auxin carriers toward neighbouring cells also having a high bifurcator level. This causes the auxin flux to bifurcate, allowing vein tips to attach to other veins creating vein loops. We explore several alternative functional forms for the flux bifurcator affecting the reallocation of efflux carriers and examine parameter dependence of the resulting vein pattern.

- by Yoh Iwasa
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- Modeling, Pattern Formation, Morphogenesis, Theoretical biology

The present study reports a highly efficient and cost effective protocol for high frequency plantlet regeneration from nodal explants of Dioscorea hispida. Nodal vine segments from 40 days old plants of Dioscorea hispida were cultured on Murashige and Skoog's (MS) medium supplemented with different concentration and combination of cytokinin i.e. 6-Benzyl Aminopurine (BAP) and auxin i.e. α-naphthalene acetic acid (NAA)

- by Kambaska Behera
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- High Frequency, Tissue culture, Cost effectiveness, Ascorbic Acid

Duboisia myoporoides R. Br. shoots were regenerated from non-organogenic and organogenic calli induced with nine different cytokinin/auxin combinations. Alkaloid colour reagents localized tropane alkaloids in the vascular regions which... more

- by Robert Close
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- Plant Biology, Ecology, Cell Differentiation, Auxin

Effects of decomposers on plant growth are generally ascribed to nutrient mobilization. However, Collembola, which are ubiquitous and abundant decomposers in soil, are known to alter root morphology with, in some cases, the nutrient content of plants remaining unaffected. We studied the interaction of Collembola (Protaphorura fimata) with the model plant Arabidopsis thaliana in order to link phenotypic responses of A. thaliana to decomposers using changes in gene expression. Collembola reduced the growth of A. thaliana during early growth stages, but this decrease was compensated later. Expression analyses revealed striking differences in the response of plant roots and shoots three and six days after exposure of Arabidopsis to Collembola. Among the specifically affected transcripts in roots, the induction of auxin-responsive genes was significantly increased after six days, suggesting that P. fimata provoked auxin-related signalling in roots. In shoots, transcriptional changes were more diverse and functional categories involved in defence and metabolic re-arrangements were significantly affected. These responses might have been related to the transitory reduction in growth which presumably was caused by Collembola feeding on and/or damaging roots. The results suggest that Collembola may improve plant resistance against the attack by herbivores by stimulating the production of secondary compounds while concomitantly compensating the costs of producing them by fostering root growth and nutrient exploitation.

- by Gerhard Welzl
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- Gene expression, Arabidopsis thaliana, Biological Sciences, Plant Resistance

The influence of the plant growth regulators 2,4-D, GA 3 , BA and kinetin, and the polyamines putrescine, spermidine and spermine were tested on axenic in vitro cultures of carposporelings of Grateloupia doryphora. The auxin 2,4-D (10 3 M) and the polyamine spermine (10 6 M and 10 3 M) induced a callus (disorganised cell mass that arose from the organised tissue of the carposporeling, as demonstrated by microscopic monitoring of the tissue). Putrescine and spermidine (10 3 M) transformed the carposporelings into cell masses that produced shoots. BA (10 3 M) and kinetin (10 6 M and 10 3 M) were inhibitory. In 10 1 M glycerol-containing culture medium, which is known to induce the formation of morphogenic cell masses, the addition of GA 3 M) resulted in the inhibition of the morphogenesis (i.e. shoot emission) in the cell mass. The kinetin at 10 6 M inhibited morphogenesis, whilst at 10 3 M inhibited even the formation of the cell masses. The combination of glycerol (10 1 M) and the auxin 2,4-D (10 6 and 10 3 M) or the polyamines putrescine, spermidine and spermine (10 6 and 10 3 M) resulted in a bigger size of the cell masses that led to a higher amount of shoots per cell mass than in glycerol alone.

- by Marta Rodrigo
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- Plant Biology, Morphogenesis, Environmental Biotechnology, In Vitro

In an attempt to optimize somatic embryo formation in Oncidium 'Gower Ramsey', the effects of five auxins (2,4-D, IAA, IBA, NAA and picloram) and five cytokinins (2iP, BA, kinetin, TDZ and zeatin), used alone, was tested in vitro using root-derived callus. In general, kinetin (0.5 and 2 mg l −1 ) and zeatin (0.5 mg l −1 ) were found to be more effective than other auxin and cytokinin treatments to induce somatic embryogenesis from root-derived callus.

- by Jen-Tsung Chen
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- Plant Biology, Somatic Embryogenesis, Auxin, Embryos

Cedrus libani, the cedar of Lebanon, is a threatened conifer native to the Levant. Over 4000 years of exploitation have resulted in the fragmentation and degradation of the Lebanese cedar populations. Continued urban and agricultural development in Lebanon adds to the difficulty of effective conservation. Two protected areas have recently been established which contain two of the more important forests: a cedar dominated forest in the Shouf region and a mixed forest at Ehden. A number of other populations are protected by ministerial decrees, and there is a need for rigorous management of all the remaining populations. The application of in vitro techniques such as somatic embryogenesis may assist in the conservation of this species. We have produced somatic pro-embryos using immature zygotic tissue as explants cultured on half-strength MS medium containing an auxin and a cytokinin (10 µM 2,4-D and 5 µM BAP). The application of somatic embryogenesis to the Lebanese cedar would be in the propagation and preservation of selected genotypes, either those from old growth provenance for use in restoration, or those with desirable commercial or horticultural characteristics.

- by Salma Talhouk
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- Agricultural Development, Ecology, Biodiversity Conservation, Somatic Embryogenesis

Protein accumulation was studied during the in vitro rooting of axillary shoots of Syringa vulgaris L. on half-strength MS medium supplemented with 7.5 mg l-1 IBA (Indole-3-butyric acid) and on auxin free one (control). The aim of the study was to determine the most appropriate duration of auxin application by monitoring protein content as a suitable marker for the rooting of Syringa vulgaris in vitro. The levels of this biochemical parameter were monitored on 12th, 24th, 36th, 48th, 60th and the 72nd hour after the beginning of the experiment. Our results showed that the protein content in auxin-treated explants was generally higher than in the control, except on the 36th hour. The beginning of root formation was indicated by a sharp decrease in total protein accumulation on IBA containing medium. On the basis of the results the most appropriate time for a transfer of in vitro cultivated shoots from inductive onto expressive rooting medium is around the 36th hour after the beginning of the cultivation.

- by Vladimir Ilinkin
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- In Vitro, IBA, Auxin, pulse treatment

Cytokinins are often considered abscisic acid (ABA) antagonists and auxins antagonists/synergists in various processes in plants. Seed enhancement (seed priming) with cytokinins is reported to increase plant salt tolerance. It was hypothesized that cytokinins could increase salt tolerance in wheat plants by interacting with other plant hormones, especially auxins and ABA. The present studies were therefore conducted to assess the effects of presowing seed treatment with varying concentrations (100, 150 and 200 mg l -1 ) of cytokinins (kinetin and benzylaminopurine (BAP)) on germination, growth, and concentrations of free endogenous auxins and ABA in two hexaploid spring wheat (Triticum aestivum L.) cultivars. The primed and non-primed seeds of MH-97 (saltintolerant) and Inqlab-91 (salt-tolerant) were sown in both Petri dishes in a growth room and in the field after treatment with 15 dS m -1 NaCl salinity. Both experiments were repeated during 2002 and 2003. Among priming agents, kinetin was effective in increasing germination rate in the salt-intolerant and early seedling growth in the salt-tolerant cultivar when compared with hydropriming under salt stress. Thus, during germination and early seedling growth, the cytokinin-priming induced effects were cultivar specific. In contrast, kinetin-priming showed a consistent promoting effect in the field and improved growth and grain yield in both cultivars under salt stress. The BAP-priming did not alleviate the inhibitory effects of salinity stress on the germination and early seedling growth in both cultivars. The increase in growth and grain yield in both cultivars was positively correlated with leaf indoleacetic acid concentration and negatively with ABA concentration under both saline and non-saline conditions. The decrease in ABA concentration in the plants raised from kinetinprimed seeds might reflect diminishing influence of salt stress. However, the possibility of involvement of other hormonal interactions is discussed.

- by Muhammad Ashraf
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- Biochemistry, Soil Science, Agronomy, Plant Biology

In vitro culture establishment, shoot proliferation and ex vitro rooting responses of Mongolian cherry (Prunus fruticosa L.), and Nanking cherry (Prunus tomentosa L.), were examined using various combinations of growth regulators. Dormant buds, taken during winter months, were used as explants. In both species, Murashige and Skoog Minimal Organic (MSMO) solid medium supplemented with 0.49 lM indole-3-butyric acid (IBA) and either 4.44 or 8.88 lM 6-benzylaminopurine (BA), was the best for culture initiation, and with 8.88-15.16 lM BA for shoot proliferation. Good rooting responses were also obtained with shoots produced on media containing 0.91 lM thidiazuron (TDZ). Auxin treatments were required for ex vitro rooting of approximately 20 mm long shoots in peat/perlite (1:1 v/v) mixture, at 25°C, under mist. The best rooting (79%) was obtained with IBA/NAA (naphthaleneacetic acid) (9.80/2.69 lM) combination. A commercial rooting powder, Rootone F, containing IBA/NAA (0.057/0.067%), was also effective (73%). The ex vitro rooted plantlets did not require any additional acclimatization prior to transplanting to the regular greenhouse conditions.

- by Kris Pruski
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- Plant Biology, Growth, In Vitro, Tissue culture

A major determinant of plant architecture is the arrangement of branches around the stem, known as phyllotaxis. However, the specific form of branching conditions is not known. Here we discuss this question and suggest a branching model... more

- by V. Volpert
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- Molecular Biology, Pattern Formation, Morphogenesis, Biological Sciences

The effect of varying light regimes on in vitro rooting ofmicrocuttings of two pear (Pyrus communis L.) cultivars was investigated. Cultures of the easy-to-root 'Conference' and the difficult-to-root 'Doyenne d'Hiver' were incubated for 21 days with or without indole-3-butyric acid (IBA) in the medium in darkness or under continuous far-red (8 /~.mol m -2 s -1 , blue, white or red (15 or 36 #mol m -2 s -~) light. 'Conference' rooted without IBA when exposed to red, blue or white light while no rooting was observed under far-red light and in darkness. The high rooting efficiency under red and, by contrast, the inhibition under far-red light and darkness suggest the involvement of the phytochrome system in rhizogenesis. The addition of IBA to the culture medium enhanced root production under all light regimes in both cultivars. Red light, especially at the lower photon fluence rate, had a positive effect by increasing root extension (number x length of roots) and stimulating secondary root formation.

- by Stefano Predieri
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- Plant Biology, Red Light, Auxin, White Light

- by Muhammad Wahid
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- Sustainable agriculture, Sustainable, Drought Stress, Environmental Sciences

The plant hormone auxin is secreted in root apices via phospholipase Dzeta2 (PLDzeta2) activity which produces specific population of phosphatidic acid that stimulates secretion of vesicles enriched with auxin. These vesicles were reported to be localized at plant synapses which are active in auxin secretion, especially at the transition zone of the root apex. There are several implications of this vesicular secretion of auxin. In root apices, auxin emerges as plant neurotransmitter-like signal molecule which coordinates activities of adjacent cells via electric and chemical signaling. Putative quantal release of auxin after electrical stimulation, if confirmed, would be part of neuronal communication between plant cells. As auxin transport across plant synapses is tightly linked with integrated sensory perception of environment, especially of omnipresent gravity and light, this process is proposed to mediate the plant perception of environment. These neuronal features allow sessile...

- by Frantisek Baluska
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- Plant Biology, Adaptive behavior, Plant growth hormone, Auxin

- by Muhammad Wahid
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- Sustainable agriculture, Sustainable, Drought Stress, Environmental Sciences

Coconut water (coconut liquid endosperm), with its many applications, is one of the world's most versatile natural product. This refreshing beverage is consumed worldwide as it is nutritious and beneficial for health. There is increasing scientific evidence that supports the role of coconut water in health and medicinal applications. Coconut water is traditionally used as a growth supplement in plant tissue culture/micropropagation. The wide applications of coconut water can be justified by its unique chemical composition of sugars, vitamins, minerals, amino acids and phytohormones. This review attempts to summarise and evaluate the chemical composition and biological properties of coconut water.

- by Jean Yong
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- Biochemistry, Organic Chemistry, Bacteriology, Cocos

Biologioal activities of humic acid (Na salt), hymatomelanic acid (Na salt), lignofulvic acid and of fulvic acids isolated from peat were studied by means of the auxin-, gibberellin-, and cytokinin- bioassays. All the four tested fractions showed higher or lower stimulating activity in these bioassays. However, the stimulating effect is considerably lower and cannot be interpreted as phytohormone activity. Some fractions in some concentrations also showed inhibitory effects. The manner of biological action of the studied fractions might bo the result of interaction of their respective components.

- by Hoang Phuong
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- Plant Biology, Humic acid, Fulvic acid, Auxin

The haploid gametophyte stage of the moss life cycle is amenable to genetic and biochemical studies. Many species can be cultured on simple defined media, where growth is rapid, making them ideal material for metabolic studies. Developmental responses to hormones and to environmental inputs can be studied both at the level of individual cells and in multicellular tissues. The protonemal stage of gametophyte development comprises cell filaments that extend by the serial division of their apical cells, allowing the investigation of the generation and modification of cell polarity and the role of the cytoskeleton in these processes. Molecular techniques including gene inactivation by targeted gene replacement or by RNA interference, together with the nearly completed sequencing of the Physcomitrella patens genome, open the way for detailed study of the functions of genes involved in both development and metabolism. 497 Annu. Rev. Plant. Biol. 2006.57:497-520. Downloaded from arjournals.annualreviews.org by David Cove on 07/07/06. For personal use only.

- by David Cove
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- Genetics, Plant Biology, Cytoskeleton, RNA interference

Kinetin (N 6 -furfuryladenine) was the first cytokinin to be isolated almost 45 years ago from DNA as an artifactual rearrangement product of the autoclaving process. Since then its chemical structure and properties have been well described. Most importantly, a wide variety of biological effects of kinetin, including those on gene expression, on inhibition of auxin action, on stimulation of calcium flux, on cell cycle, and as an anti-stress and anti-ageing compound have been reported. Recently, views on this very well known plant growth factor have undergone substantial modifications. New data have appeared which show that kinetin is formed in cellular DNA as the product of the oxidative, secondary modification of DNA. Although the biological significance of the endogenous kinetin and the molecular mechanisms of its action are not completely understood at present, most of the experimental data point toward kinetin acting as a strong antioxidant in vitro and in vivo, with potential beneficial uses in agriculture and human healthcare.

- by Gunhild Siboska
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- Plant Biology, Cell Cycle, Calcium, Plant Science
- by Walter Handro and +1
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- Plant Biology, Cell Culture, Auxin, Callus Culture

Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO 2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO 2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment; silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteins and dehydrins. Plant drought tolerance can be managed by adopting strategies such as mass screening and breeding, marker-assisted selection and exogenous application of hormones and osmoprotectants to seed or growing plants, as well as engineering for drought resistance. drought response / stomatal oscillation / osmoprotectants / hormones / stress proteins / drought management / CO 2 Plant drought stress: effects, mechanisms and management 187 Table I. Economic yield reduction by drought stress in some representative field crops. Crop Growth stage Yield reduction References Barley Seed filling 49-57% Samarah (2005) Maize Grain filling 79-81% Monneveux et al. (2005) Maize Reproductive 63-87% Kamara et al. (2003) Maize Reproductive 70-47% Chapman and Edmeades (1999) Maize Vegetative 25-60% Atteya et al. (2003) Maize Reproductive 32-92% Atteya et al. (2003) Rice Reproductive (mild stress) 53-92% Lafitte et al. (2007) Rice Reproductive (severe stress) 48-94% Lafitte et al. (2007) Rice Grain filling (mild stress) 30-55% Basnayake et al. (2006) Rice Grain filling (severe stress) 60% Basnayake et al. (2006) Rice Reproductive 24-84% Venuprasad et al. (2007) Chickpea Reproductive 45-69% Nayyar et al. (2006) Pigeonpea Reproductive 40-55% Nam et al. (2001) Common beans Reproductive 58-87% Martínez et al. (2007) Soybean Reproductive 46-71% Samarah et al. (2006) Cowpea Reproductive 60-11% Ogbonnaya et al. (2003) Sunflower Reproductive 60% Mazahery-Laghab et al. (2003) Canola Reproductive 30% Sinaki et al. (2007) Potato Flowering 13% Kawakami et al. (2006)

- by Abdul Wahid
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- Drought Stress, Environmental Sciences, Plant growth, Marker assisted selection

Plant Propagation: Basics of single and multiple rooting hormone applications. Cuttings taken from stock plants are used to propagate new plants. Using needed rooting hormones, growers are sometimes confronted with slow-to-root and hard-to-root cuttings. Multiple Rooting Solution foliar applications may improve root formation. Solutions may be applied once or multiple times in ten day to two week internals, and customized programs. Multiple solution applications use the foliar Spray Drip Down® Method which does not disturb planted cuttings.

- by Joel Kroin
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- Plant Biology, Plant Tissue Culture, Plant Physiology (Biology), Plant biotechnology

The aim of this work was to study the initiation and establishment of in vitro cultures of ‘Rocha’ and ‘Williams’ pear cultivars, as well as the in vitro rooting of micropropagated shoots and of stem discs from micropropagated shoots of ‘Rocha’.
For initiation and establishment, uninodal cuttings from growing shoots of adult trees in the field were used. The effects of salt medium, BAP concentration and ‘Rocha’ clone were studied. The percent contamination was less than 7% and 26% in ‘Rocha’ and ‘Williams’, respectively. The medium containing QL mineral salts increased the fresh and dry weights of the shoots developed from ‘Rocha’ explants, as well as the number of shoots per explant of ‘Williams’, as compared to MS salt medium. The highest BAP concentration (2 mg/ L) yielded the highest number of shoots per explant in both cultivars. ‘Rocha’ clone had a significant effect on the number of shoots per explant and on the fresh and dry weights of those shoots.
For in vitro rooting of micropropagated shoots, either juvenile shoots (Experiment 1) or shoots of adult origin (Experiment 2) were used. In these experiments different conditions of exposure to IBA were assayed which were defined by the duration of the darkness period and/or of the period during which the shoots were kept on an induction medium containing 10 µM IBA. In the experiments with stem discs, only discs from shoots of juvenile origin were used. The above conditions of exposure to IBA were assayed (Experiment 4) as well as the effect of increased IBA concentrations (from 2,5 to 20 µM) in the induction medium (Experiment 3).
A maximum of 50% rooted shoots and 12% rooted stem discs was achieved in the in vitro rooting assays. Treatment 5D (5 days with IBA in the dark) resulted in the highest shoot development and the least callus formation but gave a lower rooting percent than treatments 5D+5D (5 days with IBA in the dark + 5 days with IBA under a normal photoperiod) and 42D (six weeks with IBA, the first 5 days in darkness and the rest under normal photoperiod). The increase in the dark period duration from 5 to 10 days (treatment 10D) was detrimental to shoot and root development. In the experiments with stem discs the highest rooting percent was achieved using 10 µM IBA in the induction medium. An increase in IBA concentration increased the frequency of callus formation while the exposure treatment affected the type of callus formed (‘smooth’ or ‘filamentous’).
Key words: in vitro culture; ‘Rocha’ pear; in vitro establishment; in vitro rooting; stem discs.

- by Claudia Coelho
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- Agronomy, Micropropagation, Photoperiodism, Fotoperiodismo

Plant Propagation from Cuttings produces new plants identical to stock plants. Rooting Hormones are essential to develop roots on cuttings. This Guide describes five successful foliar and basal propagation methods: Five methods of plant propagation from cuttings:. Dry Dip, Basal Quick Dip, Foliar Spray Drip Down, Foliar Total Immerse, Basal Long Soak. The methods use the rooting hormones Hortus IBA Water Soluble Salts® (rooting solutions) & Rhizopon® AA (rooting solutions & dry powders).

Experiments were conducted on tomato to study the potential of brown alga Sargassum johnstonii as a biofertilizer. Seaweed extract was applied as a foliar spray, soil drench, and soil drench + foliar spray to assess its effect on plant growth, yield, and concentration of lycopene and vitamin C. The main objective of the study was to enhance the biochemical constituents with neutraceutical and antioxidant values in tomato fruit. Different concentrations (0.1%, 0.4%, 0.8%, 2%, 6%, 8%, and 10%; v/v) of seaweed extract were used and growth was observed over a period of 7 months. A total of 14 sprays/drenches were applied at 15-day intervals during the entire vegetative and reproductive phase. A statistically significant increase in vegetative growth (plant height, shoot length, root length, and number of branches), reproductive parameters (flower number, fruit number, and fresh weight), and biochemical constituents (photosynthetic pigments, proteins, total soluble sugars, reducing sugars, starch, phenols, lycopene, and vitamin C) was recorded following all three methods of treatment at higher concentrations of seaweed extract. The study also reports auxin- and cytokinin-like activity, and the presence of macro- (Ca, Mg, Na, and K) and micronutrients (Fe, Cu, Zn, and Mn), in seaweed extract of S. johnstonii, which makes it a potential biofertilizer.

- by inderdeep kaur
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- Plant Biology, Environmental Biotechnology, vitamin C, Applied Phycology

We introduce a class of biologically-motivated algorithms for generating leaf venation patterns. These algorithms simulate the interplay between three processes: (1) development of veins towards hormone (auxin) sources embedded in the leaf blade; (2) modification of the hormone source distribution by the proximity of veins; and (3) modification of both the vein pattern and source distribution by leaf growth. These processes are formulated in terms of iterative geometric operations on sets of points that represent vein nodes and auxin sources. In addition, a vein connection graph is maintained to determine vein widths. The effective implementation of the algorithms relies on the use of space subdivision (Voronoi diagrams) and time coherence between iteration steps. Depending on the specification details and parameters used, the algorithms can simulate many types of venation patterns, both open (tree-like) and closed (with loops). Applications of the presented algorithms include texture and detailed structure generation for image synthesis purposes, and modeling of morphogenetic processes in support of biological research.

- by Adam Runions
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- Information Systems, Leaf Growth, Auxin, Image Synthesis

We tested the feasibility of in vitro culture techniques for the propagation of the three endangered cacti species Escobaria minima (Baird) D. Hunt, Mammillaria pectinifera (Ruempler) F.A.C. Weber and Pelecyphora aselliformis Ehrenberg. Twenty-five MS-based proliferation media were tested in preliminary experiments, with different combinations of the auxin NAA and either of the cytokinins BA, kinetin or TDZ. TDZ induced a good proliferation rate, albeit associated with abundant callus formation and hyperhydricity of axillary shoots. A high multiplication rate combined with good quality proliferated shoots and little or no callus induction was observed on media containing BA for E. minima and M. pectinifera and on a medium containing kinetin for P. aselliformis. These results were also confirmed in subsequent experiments in which different explants (shoot tips, bases and longitudinal sections) were used. Micropropagated plantlets were successfully restored to the field, where they reached the flowering stage. Plantlet regeneration of M. pectinifera and P. aselliformis from callus induced on media containing TDZ, but not 2,4-D, was also achieved. #

- by Marina Tucci
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- Auxin, In vitro culture, Callus induction, Scientia

Phytohormones play a key role in the regulation of growth, development and sustainability of the plants. Phytohormones of microalgae are considered as exogenous growth regulators, affecting the tolerance to factors of abiotic and biotic stress, as well as endogenous components of microalgae affecting the processes of biosynthesis of pigments and lipids. The review analyzed and summarized published data about the peculiarities of different classes of plant hormones formation and their impact on the growth and development of microalgae. The role of auxins, abscisic acid and ethylene in the regulation of growth processes and the development of resistance to abiotic stressors in different species of microalgae are discussed.

- by Kateryna Romanenko
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- Microalgae, Ethylene, Abscisic Acid, Auxin