Trans-zeatin Riboside Research Articles

Micropropagation and root culture of Turkish endemic Astragalus chrysochlorus (Leguminosae)

Efficient micropropagation and root culture protocols were developed for the endemic Astragalus chrysochlorus Boiss. & Kotschy. A high frequency of shoot formation (100%) and maximum multiplication (13 shoots per hypocotyl explant) were achieved on Murashige and Skoog (MS) media supplemented with 0.5 mg/L trans-Zeatin riboside (ZR). By using single regenerated hypocotyl explants, rooting was achieved at a rate of 93% on MS medium containing 2% sucrose without growth regulators. High frequency callus initiation and growth were achieved when single hypocotyl explants were inoculated on MS medium supplemented with 0.5 mg/L 2,4-Dichlorophenoxyacetic acid. Plant regeneration through indirect organogenesis was achieved on MS medium supplemented with 0.5 mg/L ZR. Root cultures were successfully established in liquid MS medium containing 0.5 mg/L \alpha-Naphthaleneacetic acid. The optimised in vitro propagation, callus culture, and root culture protocols offer the possibility to use cell/root culture techniques for vegetative propagation and secondary metabolism studies on Astragalus L. species.

Nitrogen Form Alters Hormonal Balance in Salt-treated Tomato (Solanum lycopersicum L.)

Mixed nitrate/ammonium fertilization can partially alleviate the negative effects of salinity on growth of some plant species compared to all-nitrate or all-ammonium fertilization. To gain insights about the mechanisms involved, tomato (Solanum lycopersicum L. cv Moneymaker) plants were grown hydroponically for 3 weeks with two NO3−/NH4+ fertilization regimes (6/0.5 and 5/1.5; Ntotal = 6.5 mM) in the absence (control) or presence of salt stress (100 mM NaCl). Ammonium enrichment had no effect on growth and other parameters under control conditions. Under salinity, however, ammonium enrichment improved shoot and root biomass by 20% and maintained leaf PSII efficiency close to control levels. These changes were related to higher leaf K+, NO3−, and NH4+ concentrations and activities of the N-assimilatory enzymes glutamate synthase (GOGAT) and glutamine synthase (GS) in the leaves. Ammonium enrichment also attenuated the salt-induced increase in leaf abscisic acid (ABA) concentration and decrease in leaf concentrations of indole 3-acetic acid (IAA) and the cytokinins trans-zeatin (tZ) and trans-zeatin riboside (tZR). Enhanced cytokinin status was probably due to maintenance of root-to-shoot cytokinin transport and decreased leaf induction of the cytokinin-degrading enzyme cytokinin oxidase/dehydrogenase (CKX) under ammonium-enriched conditions. It is concluded that nitrogen form modifies salinity-induced physiological responses and that these modifications are associated with changes in plant hormone status.

Analysis of 2-methylthio-derivatives of isoprenoid cytokinins by liquid chromatography–tandem mass spectrometry

A sensitive and reliable high-performance liquid chromatographic method with tandem mass spectrometric detection has been developed and used for the determination of 2-methylthio-cytokinin derivatives produced by the phytopathogenic actinomycete Rhodococcus fascians. The cultivation medium containing secreted cytokinins was concentrated and subjected to a solid-phase extraction (C18 and ion-exchange). The purified samples were further separated and analyzed by HPLC-ESI–MS/MS. This allowed to achieve chromatographic resolution of six highly hydrophobic cytokinin species including 2-methylthio-isopentenyladenine, 2-methylthio-isopentenyladenosine, 2-methylthio- trans-zeatin and 2-methylthio- trans-zeatin riboside and their cis-isomers when a reversed-phase chromatographic column (C4) and a mobile phase consisting of acetonitrile and 20 mM ammonium formate, pH 5, were used. Quantification was performed by a standard isotope dilution method using a multiple-reaction monitoring (MRM) mode. In the MRM mode, limits of detection reached 20–30 fmol and linear ranges spanned four orders of magnitude. Recovery values were between 35% and 65% and the analytical accuracy between 95% and 149%. The proposed bioanalytical method, which takes advantage of effective chromatographic separation of six 2-methyltio-derivatives (including isomers of zeatin-type cytokinins) and sensitive mass spectrometric detection, may become useful for plant biologists studying the significance of these substances in plant–microbe interactions.

Inter-ramet Photosynthate Translocation in Buffalograss under Differential Water Deficit Stress

Understanding the effect of photosynthate translocation on the shoot density of buffalograss (Buchloe dactyloides) is very important to improve its turf quality. The objective of this study was to examine the effects of water stress on water transport patterns, endogenous hormone distribution and allocation, and photosynthate allocation for connected buffalograss ramets. Clones from a single parent plant of ‘Texoka’ buffalograss were used to generate three-ramet units. Ramets are members of a clone that are not independent from the parent plant. Each water stress treatment had one of the three ramets cultured in half-strength Hoagland solution with 30% of polyethylene glycol (PEG) of −1.2 MPa ψS, while the other two ramets were kept in half-strength Hoagland solution with ψS of −0.05 MPa. Results indicated that inter-ramet water integration happened when one of the connected ramets was under water stress. Transzeatin riboside content decreased in roots treated with PEG. Abscisic acid content increased in the roots of all treatments compared with the control. Water stress caused a reduction of indole-3-acetic acid content in shoots and roots, especially the ramet stressed. Gibberellic acid content in shoots and roots of all treatments increased compared with the control. Within the control, young ramets were sinks of photosynthate, but translocation toward older ramets was detected using 14CO2 label when the older ramet was under stress. Xylem, phloem, and parenchyma cells were probably involved in the physiological integration of these responses. Fates of connected clonal ramets of buffalograss were interrelated and the agronomic significance of this result should be evaluated further.

Cultivo in vitro del mortiño (<em>Vaccinium floribundum</em> Kunth)

Debido al potencial agrícola y económico que tiene el mortiño (Vaccinium floribundum Kunth) para el Ecuador, esta investigación tuvo como objetivo establecer métodos de pro­pagación in vitro de esta especie como germinación de semillas y brotación de yemas axilares. Se utilizó un medio basal sin hormonas, Woody Plant Medium [1] modificado (mWPM), en el que las semillas germinaron con hasta un 60.7% de eficiencia. Para el subcultivo de plántulas germinadas in vitro , se usó una citoquinina fuerte, la trans zeatina ribóside, TZR (1 mg/l) en combinación con ácido a-naftalenacético, NAA (0.05 mg/l). El medio basal sin hormonas o con 2iP, 6-(gamma,gamma-dimetilalilamino) purina, permitió la elongación de las plántulas germinadas in vitro y su enraizamiento. La aclimatación de las plantas de mortiño cultivadas in vitro aún no está estandarizada y se requiere mayor investigación para encontrar los factores necesarios para completar satisfactoriamente este proceso. Para la introducción in vitro de yemas axilares se desinfectaron los extremos apicales de tallos de mortiño, y se los introdujo en medio mWPM suplementado con TZR (7 mg/l) en combinación conNAA, (0.1 mg/l). Las yemas brotadas se subcultivaron en me­dios que contenían 2iP (3 ó 5 mg/l) para su propagación y elongación. Esta investigación representa un estudio piloto para el cultivo in vitro del mortiño, sentando las bases para futuras investigaciones con esta especie.

Occurrence of plant growth regulators in Psilotum nudum

The endogenous content of the auxin indole-3-acetic acid (IAA), the cytokinins trans-zeatin (tZ), trans-zeatin riboside (tZR), dihydrozeatin (DHZ), dihydrozeatin riboside (DHZR), isopentenyladenine (iP) and isopentenyladenosine (iPR), the gibberellins GA 1, GA 3, GA 4, GA 7, GA 9 and GA 20 in the rhizome and aerial shoots during and after sporogenesis were measured by high-performance liquid chromatography–tandem mass spectrometry in the fern Psilotum nudum. The present study shows, for the first time, the presence of the auxin IAA, the cytokinins tZR, DHZR and iP, and the gibberellins GA 4, GA 9 and GA 20 in the rhizome and aerial shoots of this species and suggests a possible role of gibberellins in the evolution of ferns.

Biochemical, molecular characterization and growth promoting effects of phosphate solubilizing Pseudomonas sp. isolated from weeds grown in salt range of Pakistan

Three species of phosphate solubilizing bacteria viz, Pseudomonas mendocina Khsr2, Pseudomonas stutzeri Khsr3 and Pseudomonas putida Khsr4 were isolated from roots of weeds Lactuca dissecta D. Don, Solanum surattense Burm. f and Sonchus arvensis L. respectively growing in Khewra salt range (EC: 2.3 dS m−1; pH 8.6). Preliminary identification of bacterial isolate was made on the basis of morphological and biochemical characters and confirmed by partial 16S-rRNA gene sequencing. The genetic diversity among the isolates was evaluated by Randomly Amplified Polymorphic DNA finger printing and similarity matrix was measured. All the Pseudomonas sp. were capable of solubilizing phosphate, produced phytohormones: Indole-3-acetic acid, Gibberellic acid, Trans-zeatin riboside and Abscisic acid in culture media and were found to be efficient in stimulating root/shoot length and dry weight and proline contents of Zea mays L (advance germplasm line: Islamabad Gold) seedlings grown under normal and NaCl (20 dS m−1) stress. The strain Pseudomonas stutzeri Khsr3 appears to be a potential candidate as bio-inoculant for saline fields.

Azospirillum strains isolated from roots and rhizosphere soil of wheat (Triticum aestivum L.) grown under different soil moisture conditions

The present study deals with the isolation and characterization of Azospirillum strains isolated from roots and rhizosphere soil of wheat (at tillering and anthesis stages) plants grown under different moisture regimes in the field and in pots. The survival of Azospirillum isolates from plants of irrigated field and those from well-watered pots was higher than that of Azospirillum strains isolated from roots and rhizosphere soils of plants grown under arid and semiarid (14–8% soil moisture) field conditions and under water-stressed (8% soil moisture) conditions in pots. On the basis of carbon/nitrogen source utilization, the Azospirillum strains isolated from wheat under field and pot conditions were grouped in three groups. The unweighted pair group method with arithmetic means cluster analysis based on random amplification of polymorphic DNA showed that two groups of Azospirillum were similar. The strains isolated from plants (at tillering stage) grown under low moisture conditions either in pots or in field were genetically similar to strains isolated from plants grown under well-watered conditions in both pots and field. Inoculation of wheat with isolates from water-stressed plants induced tolerance to water stress in inoculated plants. Isolates from water-stressed conditions exhibited lower production of indole acetic acid, gibberellic acid, and trans zeatin riboside but a higher production of abscisic acid.

AtSOFL1 and AtSOFL2 Act Redundantly as Positive Modulators of the Endogenous Content of Specific Cytokinins in Arabidopsis

BackgroundAlthough cytokinins have been known for decades to play important roles in the regulation of plant growth and development, our knowledge of the regulatory mechanism of endogenous content of specific cytokinins remains limited.Methodology/Principal FindingsHere, we characterized two SOB five-like (SOFL) genes, AtSOFL1 and AtSOFL2, in Arabidopsis (Arabidopsis thaliana) and showed that they acted redundantly in regulating specific cytokinin levels. Analysis of the translational fusion AtSOFL1:AtSOFL1-GUS and AtSOFL2:AtSOFL2-GUS indicated that AtSOFL1 and AtSOFL2 exhibited similar expression patterns. Both proteins were predominantly expressed in the vascular tissues of developing leaves, flowers and siliques, but barely detectable in roots and stems. Overexpression of either AtSOFL1 or AtSOFL2 led to increased cytokinin content and obvious corresponding mutant phenotypes for both transgenic seedlings and adult plants. In addition, overexpression and site-directed mutagenesis experiments demonstrated that the SOFL domains are necessary for AtSOFL2's overexpression phenotypes. Silencing or disrupting either AtSOFL1 or AtSOFL2 caused no obvious developmental defects. Endogenous cytokinin analysis, however, revealed that compared to the wild type control, the SOFL1-RNAi62 sofl2-1 double mutant accumulated lower levels of trans-zeatin riboside monophosphate (tZRMP) and N6-(Δ2-isopentenyl)adenosine monophosphate (iPRMP), which are biosynthetic intermediates of bioactive cytokinins. The double mutant also displayed decreased response to exogenous cytokinin in both callus-formation and inhibition-of-hypocotyl-elongation assays.Conclusions/SignificanceTaken together, our data suggest that in plants AtSOFL1 and AtSOFL2 work redundantly as positive modulators in the fine-tuning of specific cytokinin levels as well as responsiveness.

English

  Present investigation was made to isolate and characterize plant growth promoting rhizobacteria (Rkh1 - Rkh4) from rhizosphere of four weeds: Chrysopogon aucheri,Lactuca dissecta, Solanum surratense and Sonchus arvensis thriving under high salinity (EC: 2.3 dS/m) of Khewra salt range and the results were compared with strain Rak isolated from rhizosphere (EC: 0.2 dS/m) of Solanum surratense grown in arid area of district Attock. The tolerance of all the strains was checked against the salt present in culture media in the form of rhizospheric soil filtrate of weeds collected from Khewra salt range. The nutrient contents of rhizospheric soil of weeds were measured. All the strains were capable to produce phytohormones indole-3-acetic acid (IAA), gibberellic acid (GA3), trans-zeatin riboside (t-zr) and abscisic acid (ABA) in the culture media. Inoculation of strains on soybean seedlings treated with or without 20 dS/m NaCl resulted in better growth and higher proline contents than control plants. The strains isolated from weeds of Khewra salt range particularly Rkh3 appears more promising for potential biofertilizers in saline fields.   Key words: Plant growth promoting rhizobacteria, nutrient contents, salt tolerance, phytohormones production, proline contents.

Endogenous hormone levels in bearing and non-bearing shoots of walnut (Juglans regia L.) and their mutual relationships

The levels of endogenous gibberellic acid equivalents, indole acetic acid, trans-zeatin and trans-zeatin riboside in bearing and non-bearing shoots of walnut (Juglans regia L.) were detected by high-performance liquid chromatography during vegetation period. The levels of endogenous hormones were analysed in four different shoot types of current season, bearing terminal shoot, non-bearing terminal shoot, bearing lateral shoot and non-bearing lateral shoot. Their average levels differed statistically at five sampling times from 25 May to 23 September. Relationships among changes in endogenous gibberellin, auxin and cytokinin contents were computed using correlation and regression analyses. Remarkable positive correlation coefficients were found among changes in gibberellin, auxin and cytokinin contents. Statistical findings indicated that changes in endogenous hormones exhibited a collective behaviour in walnut shoots during vegetation period.

Transgenic grapefruit plants expressing the PAPETALA3-IPT gp gene exhibit altered expression of PR genes

Transgenic grapefruit plants (Citrus paradisi cv. ‘Duncan’) with the isopentenyltransferase (ipt) gene under the control of APETALA3 promoter have been produced using Agrobacterium-mediated transformation. The relative expression level of the ipt gene was between 2.3 and 7 times higher in transformed plants than in the wild-type but despite the presence of a tissue-specific promoter, the expression was not limited only to flower tissue. Increased levels of trans-zeatin riboside between 9.4 and 32-fold found in transgenic grapefruit were considered the consequence of ectopic expression of the ipt gene. Chlorophyll levels in fully expanded uppermost leaves were also about 30% higher in transgenic than in wild-type plants. Involvement of cytokinins in control of expression of three pathogenesis-related protein genes: β-1,3-glucanase, a stress related PR gene 24P220, and an acidic chitinase, 24P262 was examined. Expression of β-1,3-glucanase, and 24P220 gene were significantly enhanced in transgenic plants while the expression of chitinase was reduced to low levels. Our results confirm the effect of cytokinins on expression of genes implicated in the response of grapefruit plants to pathogen attack and suggest a possible role of cytokinins in pathogen resistance.

HIGH-THROUGHPUT SCREENING TECHNOLOGY FOR MONITORING PHYTOHORMONE PRODUCTION IN MICROALGAE(1).

New miniaturized techniques for multiplying microalgae and estimating their phytohormone production were developed; in these methods, the strains to be tested are cultivated in microtitre plates, and the phytohormones in suspensions of the cultures are measured by direct ELISAs. Specific and sensitive ELISAs for determining abscisic acid (ABA), indole-3-acetic acid (IAA), cis- and trans-zeatin riboside, isopentenyladenosine (iPR), and other less common cytokinins were developed for this purpose. Polyclonal antibodies used in the ABA and IAA assays were raised against C1- and C1'- conjugates of the compounds with BSA, respectively, and thus were specific for the free acids and their respective C1-derivatives. The use of cytokinin ribosides coupled via their sugar residues to BSA as haptens generally led to antibodies that bound free bases, 9-glycosides and nucleotides, but with high specificity for the corresponding N(6) -side chains. Using internal standards, dilution assays, and authentic [(2) H] and [(3) H] recovery markers, it was shown that the ELISAs could be used to estimate contents of the selected phytohormones in the cultures. The ELISAs provided reliable and very fast estimates of the selected phytohormones, at concentrations ranging from 0.01 to 10 pmol · mL(-1) in various microalgal strains. In addition, a recently developed HPLC selected ion monitoring mass spectrometry (HPLC-SIM-MS) method was used to calibrate and validate the ELISA results and confirm the presence of the detected phytohormones in immunoaffinity-purified extracts. Where independent validation of results is deemed necessary, the use of quantitative HPLC-MS is recommended for each new microalgal strain to be tested.

The effect of cytokinins on growth and sexual organ development in the gametophyte of Blechnum spicant L.

In this study, we report the role of exogenous and endogenous cytokinins on growth and sexual organ development in the fern Blechnum spicant L. Spore-derived gametophytes (SG) were cultured in full-strength Murashige and Skoog (1962) liquid medium supplemented with (a) 4.44 μMN6-benzyladenine (BAP), (b) a crude extract from mature female gametophytes, and (c) 4.44 μM BAP in combination with the crude extract from mature gametophytes, respectively. Both BAP and the crude extract delayed the gametophyte development, and this effect was increased when they were added together. With respect to sexual organ development, BAP inhibited the sexual organ formation, while the crude extract favored antheridia formation; however, when added together, the percentage of antheridia decreased. The endogenous level of the cytokinins cis-zeatin (cZ), cis-zeatin-riboside (cZR), dihydrozeatin (DHZ), dihydrozeatin riboside (DHZR), isopentenyl adenine (iP), isopentenyl adenosine (iPR), isopentenyl-9-glucoside (iP9G), trans-zeatin (tZ), and trans-zeatin riboside (tZR) were analyzed in female and male gametophytes of B. spicant L. The endogenous levels of cytokinins tZ, cZ, DHZ, cZR, iP, and iPR were higher in female gametophytes than in male gametophytes, with the endogenous iP and iPR content being increased more than 300 and 400 times, respectively.

T-DNA Activation Tagging as a Tool to IsolateSalvia miltiorrhizaTransgenic Lines for Higher Yields of Tanshinones

The study of functional genomics has paved the way for directed approaches to the generation of genetically modified plants that produce novel and/or improved yields of pharmaceuticals. In the present study, an activation tagging mutagenesis (ATM) population of Salvia miltiorrhiza Bunge, a medicinal plant, was established by Agrobacterium-mediated transformation. The optimum conditions for Agrobacterium transformation were determined by the expression of green fluorescent protein. Under these optimized conditions, we isolated 1435 ATM cell lines with our initial antibiotic selection. Of these 1435 ATM cell lines, six lines (T1-T6) showed a red color on a selective medium containing 4.5 microM 2,4-dichlorophenoxyacetic acid (2,4-D), which is used as a phenotypic model system to identify the accumulation of tanshinones. 700 out of 1435 ATM cell lines were tested with a beta-glucuronidase (GUS) assay, 35 showed GUS activity. Southern blotting analysis revealed that the T1-T7 ATM cell lines have a single copy of the T-DNA insertion. Comparative analysis by high-performance liquid chromatography of the tanshinones expressed by non-transformed and ATM-transformed calli revealed varying quantities of tanshinones. There were negligible tanshinones in non-transformed white calli induced with 2,4-D. ATM lines T1-T6 showed significant increases in the yields of tanshinone-I (up to 43-fold), tanshinone-IIA (up to 26-fold) and cryptotanshinone (up to 104-fold) compared with those of the non-transgenic lines on 2,4-D medium. Interestingly, the yield of cryptotanshinone from line T4 on 2,4-D medium was two times higher than that of the non-transgenic lines on Trans-zeatin riboside medium. To the best of our knowledge, this is the first report of a quantitative and qualitative improvement in quinoid diterpene production achieved in a medicinally important plant species by activation tagging.

Separation of cytokinin isomers with a partial filling‐micellar electrokinetic chromatography‐mass spectrometry approach

A new method based on partial filling-MEKC (PF-MEKC) directly coupled to ESI-MS was developed for the simultaneous separation and determination of 13 structurally similar cytokinins, including various geometric and positional isomers of cytokinins. On the basis of the resolution of the neighboring isomer peaks, different parameters (i.e., pH and concentration of buffer, surfactant concentrations, length of the injected micellar plug, organic modifier, and applied separation voltage) were optimized to achieve a satisfactory PF-MEKC separation. Under optimum conditions, the separation of 13 cytokinin standards was accomplished within 25 min. MS/MS with multiple reaction monitoring detection was carried out to obtain sufficient selectivity. PF-MEKC-MS/MS allowed for the direct identification and confirmation of the cytokinins present in banana (Musa spp.) pulp sample after extraction and purification. Finally, trans-zeatin riboside (ZR) and trans-zeatin (Z) were unambiguously identified in banana pulp. It is anticipated that the current PF-MEKC-MS method can be applied to analyze cytokinins in a wide range of biological samples.

Expression of class I knotted1-like homeobox genes in the storage roots of sweetpotato ( Ipomoea batatas)

As a first step in clarifying the involvement of class I knotted1-like homeobox (KNOXI) genes in the storage root development of sweetpotato (Ipomoea batatas), we isolated three KNOXI genes, named Ibkn1, Ibkn2 and Ibkn3, expressed in the storage roots. Phylogenetic analysis showed that Ibkn1 was homologous to the SHOOT MERISTEMLESS (STM) gene of Arabidopsis, while Ibkn2 and Ibkn3 were homologous to the BREVIPEDICELLUS (BP) gene. Of these, expression of Ibkn1 and Ibkn2 were upregulated in developing and mature storage roots compared with fibrous roots. Ibkn1 and Ibkn2 showed different expression patterns in the storage roots. Ibkn1 was preferentially expressed at the proximal end and around the primary vascular cambium, while Ibkn2 expression was highest in the thickest part and lower in both the proximal and distal ends. In contrast to Ibkn1 and Ibkn2, expression of Ibkn3 in roots was not consistent among sweetpotato cultivars. The distribution of endogenous trans-zeatin riboside (t-ZR) in sweetpotato roots showed a similarity to the expression pattern of KNOXI genes, supporting the idea that KNOXI genes control cytokinin levels in the storage roots. The physiological functions of these KNOXI genes in storage root development are discussed.

Effects of application of sucrose and cytokinin to roots on the formation of tuberous roots in sweetpotato (Ipomoea batatas (L.) Lam.)

Effects of sucrose and cytokinin (trans-zeatin riboside (t-ZR)) on the formation of tuberous root of sweetpotato (Ipomoea batatas (L.) Lam.) were studied by directly applying these substances to young roots. In the roots that originally contained approximately 9 μg of en- dogenous sucrose per milligram of fresh weight (FW), further increase in the sucrose level did not necessarily result in tuberous root formation, whereas t-ZR application invariably induced tuberous root formation. However, t-ZR did not induce morphogenesis when the sucrose level in the root was lowered to approximately 2 μg mg -1 of FW. Our results imply that high levels of en- dogenous sucrose are necessary for tuberous root formation and that in the presence of high sucrose concentrations, cytokinins can trigger tuberous root formation.

Hormone Profiling by LC-QToF-MS/MS in Dormant Macadamia integrifolia: Correlations with Abnormal Vertical Growth

A method for analyzing multiple plant hormone groups in small samples with a complex matrix was developed to initiate a study of the physiology of abnormal vertical growth (AVG) in Macadamia integrifolia (cv. HAES344). Cytokinins (CKs), gibberellins (GAs), abscisic acid (ABA), and auxins were detected in xylem sap and apical and lateral buds using high-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry (LC-QToF-MS/MS). The extraction method separated compounds with high sensitivity in positive (CKs) and negative (ABA, auxins, GAs) modes of QToF-MS/MS. CK profiles differed in xylem sap and apical and lateral buds irrespective of AVG symptoms. Trans-zeatin riboside (t-ZR) was dominant in sap of normal and AVG trees (∼4 and 6 pmol g−1 FW, respectively). In apical buds isopentenyl adenine (iP) (∼30 pmol g−1 FW) was the most abundant CK, and in lateral buds trans-zeatin (t-Z) (22–24 pmol g−1 FW) and iP (24–30 pmol g−1 FW) were the most abundant. t-Z levels of AVG trees were higher in apical buds (13.88 vs. 6.6 pmol g−1 FW, p < 0.05) and lower in sap (0.16 vs. 0.51 pmol ml−1, p < 0.005) compared to normal trees. ABA in lateral buds was 1.9 times higher (p < 0.001) in AVG. IAA was below quantification, whereas indole-3-butyric acid (IBA) was consistently present. GA7 was the dominant GA in apical and lateral buds of all trees (100–150 pmol g−1 FW). GA3, 4, & 9 were consistently present at low concentrations (<12 pmol g−1 FW) in buds. GAs1, 3, & 9 were detected in xylem sap at low concentrations (<0.5 pmol g−1 FW). Differences in sap amino acids (AA) were also assessed. In sap from AVG trees, asparagine and glutamine increased significantly (p < 0.05) in their contribution to total AA. Potential AVG hormone correlations are discussed.

Plant Hormones Isolated from “Katahdin” Potato Plant Tissues and the Influence of Photoperiod and Temperature on Their Levels in Relation to Tuber Induction

Qualitative and quantitative analyses were carried out on vegetative tissues of potato (Solanum tuberosum cv. “Katahdin”) in search of natural products thought to play a role in tuber induction. Tissues were obtained from plants initially grown in a growth chamber under noninducing conditions (30°C day and 28°C night with an 18-h photoperiod), and then half of the plants were moved to inducing chambers (28°C day and 13°C night with a 10-h photoperiod) for 10 days prior to tissue harvest. Plants from each chamber were then harvested at 2-day intervals for 10 days, separated into above- and belowground portions, and the lyophilized tissues were extracted and subjected to rigorous purification and separation using high-performance liquid chromatography. This was followed by identification and quantification using combined gas chromatography-mass spectrometry. Compounds isolated and identified included gibberellic acid; cytokinins cis-zeatin riboside, trans-zeatin, trans-zeatin riboside, and isopentenyladenine; and jasmonates jasmonic acid, tuberonic acid and its methyl ester, methyl 7-isocucurbate, and 9,10-dihydromethyljasmonate. Methyl 7-isocucurbate and 9,10-dihydromethyljasmonate were detected for the first time in potato tissue as endogenous compounds. Cytokinin and jasmonate levels generally increased under inducing conditions, whereas gibberellic acid levels declined progressively during the 10-day sampling period. Only gibberellic acid, jasmonic acid, and cis-zeatin riboside levels were significantly influenced by induction.