Concentrations Of Zeatin Research Articles

Mechanisms of Tiller Occurrence Affected by Exogenous IAA,GA 3 ,and ABA in Wheat with Different Spike-types

Two winter wheat cultivars,Shannong 15 and Shannong 8355,were used to study the effects of exogenous indole-3-acetic acid(IAA),gibberellic acid 3(GA3),and abscisic acid(ABA)on tiller occurrence in wheat and the underlying mechanism.Exogenous IAA and GA3 inhibited occurrence of wheat tiller,while exogenous ABA reduced the rate of tiller occurrence.Furthermore,exogenous IAA and GA3 completely inhibited growth of tiller bud,while exogenous ABA significantly slowed the growth rate of tiller bud.The growth of tiller bud was positively correlated with content of zeatin(ZT),but negatively correlated with IAA content and ratios of IAA/ZT and ABA/ZT.In contrast,the growth of tiller bud had slightly negative correlations with GA3 and ABA contents.These results suggest that IAA and ZT play a key role in regulating tiller occurrence in wheat,and exogenous hormones regulate the growth of tiller bud through changing contents of IAA and ZT and the ratios of IAA/ZT and ABA/ZT in tiller node.

Micropropagation of Arbutus unedo, A. andrachne, and their natural hybrid, A. x andrachnoides from seedling explants

SummaryMicropropagation of Arbutus unedo, A. andrachne, and A. x andrachnoides could facilitate their use as ornamental, forestry and medicinal plants, while the use of in vitro-grown seedlings as stock material could solve contamination and seasonality problems. Seeds germinated at high rates (87 – 99%) at 15ºC on half-strength Murashige and Skoog (MS) medium after 24 – 30 d, depending on the species. Nodal explants were excised from 2-month-old seedlings grown on MS medium or on woody plant medium (WPM) salts supplemented with 100 mg l–1 myo-inositol, 1.0 mg l–1 thiamine, 0.5 mg l–1 pyridoxine, and 0.5 mg l–1 nicotinic acid, containing 1.0 mg l–1 indole-3-butyric acid (IBA). Multiple shoots were produced from each initial culture, and from subsequent sub-cultures on MS medium or on WPM containing 2.5 or 5.0 mg l–1 zeatin (ZEA). The use of thidiazuron (TDZ) at 0.2 or 2.0 mg l–1, instead of ZEA, resulted in a reduced response and fewer shoots per explant. In addition, these TDZ-treated shoots had malformations and were very short, making them unsuitable for multiplication. The rates of multiplication on both media containing 2.5 or 5.0 mg l–1 ZEA were six- to seven-fold higher than on TDZ-containing or hormone-free media. MS medium resulted in higher rates of shoot production than WPM (4.4 – 7.8 vs. 2.2 – 5.3 shoots per explant, respectively, depending on the species and concentration of plant growth regulator) for cultures with a higher shoot proliferation potential. In contrast, WPM induced higher rooting percentages and more roots per micro-shoot (82 – 97% and 4.5 – 8.5, respectively, depending on the species and IBA concentration) compared to MS medium (42 – 64% and 3.1 – 4.1, respectively). A. x andrachnoides had a proliferation potential (4.6 shoots per explant on average on both media and ZEA concentrations) that was between the two parental species (5.9 and 3.4 shoots per explant for A. andrachne and A. unedo, respectively). Ex vitro acclimatisation and survival of plantlets in a 1:1 (v/v) mix of peat:perlite was highly successful (92 – 100%).

The low fertility of Chinese white poplar: dynamic changes in anatomical structure, endogenous hormone concentrations, and key gene expression in the reproduction of a naturally occurring hybrid

KEY MESSAGE : We report that low fertility during intraspecific hybridization in Chinese white poplar was caused by prefertilization barriers, reduced ovules, and embryonic abortion. Hormone concentrations and gene expression patterns were also evaluated during the fertilization process. Hybrid vigor holds tremendous potential for yield increases and trait improvement; however, some hybridization combinations within Populus show very low fertility. To explore the causes of this low fertility in intraspecific hybridization of Chinese white poplar, we examined anatomical structure, hormone levels and expression of key genes in two unique crossing combinations of Populus×tomentosa "Pt02"×P.×tomentosa "LM50", and (P.×tomentosa×P. alba cv. bolleana "Ptb")×P.×tomentosa "LM50". The seed set potential in the intraspecific hybridization P.×tomentosa "Pt02"×P.×tomentosa "LM50" was quite low, which was likely caused by prefertilization barriers, reduced ovule numbers, and embryonic abortion in ovaries. During intraspecific hybridization, we found reduced indoleacetic acid (IAA) in pistils, which may cause pollen tube deformations and increased IAA in heart-stage embryos, which may affect embryo development. Gibberellin A3 (GA3) decreased from the zygote dormancy stage to globular-stage embryos, which may be caused by failure of fertilization in specific embryos. The maximum zeatin (Z) concentration was found in heart-stage embryos, but Z concentrations quickly decreased, which may affect endosperm development. Increasing concentrations of abscisic acid (ABA) during zygote dormancy and eight-cell proembryo stages likely induced abscission of the infructescence. High ABA concentrations also regulated embryo maturity. Measurement of genes expression showed that high expression of SRK and/or SLG may result in rejection of pollen by stigmatic papillae through a mechanism, reminiscent of self-incompatibility. Also, low expression of LEC1 and FUS3 may cause embryonic abortion. Identification and eventual bypassing of these barriers may allow future genetic improvement of this key woody crop species.

Physiological Responses of the Green Manure, Vicia Sativa , to Drought

Cover crops and green manures have been adopted in rainfed agriculture for providing soil protection between cultivation seasons and for increasing soil nutrient and organic matter content. A greenhouse experiment was conducted to evaluate physiological responses of the green manure Vicia sativa to drought. The gravimetric leaf water of content of 80% did not decrease during 24 days of water withholding. Gas exchange was very sensitive to drought. For instance, net CO2 uptake of 7.8 ± 0.17 ?mol m-2 s-1 started decreasing at eight days of water withholding but recovered when the plants were re-watered. While total chlorophyll was not signifi cantly degraded for the droughted plants, these individuals accumulated 1,000-fold the proline of the control, which amounted to 0.41 ± 0.09 ?mol g-1. Raman spectroscopy revealed differences in the accumulation of metabolites at 24 days of water withholding between well-watered and droughted plants, including a higher content of abscisic acid, gibberellic acid, indoleacetic acid, and zeatin. Vicia sativa can tolerate month-long droughts and can be considered as a useful alternative for increasingly arid locations.

Effects of Engineered Sinorhizobium meliloti on Cytokinin Synthesis and Tolerance of Alfalfa to Extreme Drought Stress

Cytokinin is required for the initiation of leguminous nitrogen fixation nodules elicited by rhizobia and the delay of the leaf senescence induced by drought stress. A few free-living rhizobia have been found to produce cytokinin. However, the effects of engineered rhizobia capable of synthesizing cytokinin on host tolerance to abiotic stresses have not yet been described. In this study, two engineered Sinorhizobium strains overproducing cytokinin were constructed. The tolerance of inoculated alfalfa plants to severe drought stress was assessed. The engineered strains, which expressed the Agrobacterium ipt gene under the control of different promoters, synthesized more zeatins than the control strain under free-living conditions, but their own growth was not affected. After a 4-week inoculation period, the effects of engineered strains on alfalfa growth and nitrogen fixation were similar to those of the control strain under nondrought conditions. After being subjected to severe drought stress, most of the alfalfa plants inoculated with engineered strains survived, and the nitrogenase activity in their root nodules showed no apparent change. A small elevation in zeatin concentration was observed in the leaves of these plants. The expression of antioxidant enzymes increased, and the level of reactive oxygen species decreased correspondingly. Although the ipt gene was transcribed in the bacteroids of engineered strains, the level of cytokinin in alfalfa nodules was identical to that of the control. These findings suggest that engineered Sinorhizobium strains synthesizing more cytokinin could improve the tolerance of alfalfa to severe drought stress without affecting alfalfa nodulation or nitrogen fixation.

Impact of arbuscular mycorrhizal fungi on the growth and related physiological indexes of Amorpha fruticosa

Through inoculating Amorpha fruiticosa with arbuscular mycorrhizal (AM) fungi and without, the seedlings’ growth indexes, dynamic characteristics of plant endogenous hormone levels, soluble sugar contents in roots and in leaves respectively, and physiological characteristics of seedlings utilizing nitrogen (N), phosphorous (P), were systematically studied. The results showed that both the two tested AM fungi strains, Glomus mosseaeand Glomus intraradices, could colonize the A. fruiticosa roots forming mycorrhizal complexes, and G. mosseae found to be the best AM fungus for A. fruiticosa had a better colonization compatibility than G. intraradices on A. fruiticosa roots with colonization percentage up to 88.5% that of the highest. On the one hand, inoculation with AM fungi could obviously elevate seedling heights, root collar diameter and dry biomass which were 1.94, 1.56 and 1.68 times that of control seedlings when A. fruiticosa seedlings inoculated with G. mosseae at the last stage of seedling growth (110 days). On the other hand, the soluble sugar contents in roots and leaves of seedlings inoculated with AM fungi were significantly higher than control treatments, having a positive correlation with colonization percentage. In addition, AM fungi dramatically increased the contents of auxin (IAA), gibberellin (GA) and zeatin (ZR) in roots, but had little impact on abscisic acid (ABA). Furthermore, AM fungi inoculation not only improved per seedling total N, P contents, but also significantly increased the soluble N, P concentration of rhizosphere soil. Key words: Arbuscular mycorrhizal fungi, Amorpha fruiticosa, soluble sugar, endogenous hormone, N, P element.

Determination of Endogenous Hormones Content in Cotton Varieties (Gossypiumhirsutum) as Influenced by Phosphorus and Potassium Nutrition

Two experiments were conducted to evaluate the endogenous hormones content of cotton plants grown hydroponically, and supplied with varying levels of phosphorus (P) and potassium (K) mineral nutrients in the first cropping. In the second cropping, varying levels of exogenous indole-3-acetic acid (IAA), gibberellic acid (GA3) and zeatin (Z) and their combinations were applied to high level of PK in the hydroponic. In the first experiment, low K and low P treated plants had higher content of gibberellic acid (GA3) in the leaves than high PK treated plants, and low K treated plants also produced more Zeatin (Z) in the leaves than either low P or high PK treated plants. Furthermore, low K treated plants had higher Zeatin (Z) content in the root than either low P or high PK treated plants. However, the two cotton varieties expressed different hormones content in the leaves, stem and root. In the second experiment, GA3 concentration was highest in the cotton stem treated to IAA x GA3 x Z. Moreover, Zeatin content in the leaves, stem and root was highest in the cotton treated to IAA x GA3 x Z and 2IAA x 2GA3 x 2Z for leaves, IAA x GA3 x Z for stem and Z, IAA x 2GA3 x Z for root. Nevertheless, two cotton varieties possessed different hormones content in the leaves, stem and root. In general, there was no relationship between the first cropping and second cropping. The results demonstrated influence of exogenous hormones application in altering the endogenous hormones content of cotton plants.

Shoot Regeneration and Plantlet Formation by Cascade Huckleberry, Mountain Huckleberry, and Oval-leaf Bilberry on a Zeatin-containing Nutrient Medium

A plant regeneration protocol was developed for cascade huckleberry (Vaccinium deliciosum), mountain huckleberry (V. membranaceum), and oval-leaf bilberry (V. ovalifolium) clones. The effects of zeatin concentrations (0, 4.6, 9.1, and 13.7 μM) and explant type (leaf or stem segment) on adventitious shoot regeneration were studied on a nutrient medium of low ionic concentration. Adventitious bud and shoot regeneration was greatly influenced by clone, explant type, and zeatin concentration. Zeatin at 9.1 to 13.7 μM supported the best bud and shoot regeneration. At low concentrations (2.3 to 4.6 μM), zeatin enhanced shoot elongation and produced usable shoots after one additional subculture. The three clones differed significantly with respect to multiplication rate of adventitious shoots. Oval-leaf bilberry and mountain huckleberry clones produced six to seven 5-cm-long shoots per explant and cascade huckleberry clone produced five 3-cm-long shoots per explant, when 2.3 μM zeatin was used in the medium. Increasing the concentration of zeatin in the culture medium increased shoot number per explant, but decreased shoot height, leaf number per shoot, and shoot vigor. Proliferated shoots were rooted on the same medium but without any plant growth regulators (PGRs). Rooted plantlets were transferred to a 2 peat:1 perlite (v/v) medium for acclimatization and eventually established in the greenhouse with 75% to 90% survival rate. This in vitro protocol will be useful for micropropagation, in vitro selection, and genetic manipulation of Vaccinium species.

Endogenous auxin level is a critical determinant for in vitro adventitious shoot regeneration in potato (Solanum tuberosum L.)

Endogenous levels of indole-3-acetic acid (IAA) were determined in the internodal explants of Indian tetraploid potato cultivars (cvs) viz., Kufri Sutlej (K.Sutlej) and Kufri Giriraj (K.Giriraj). Seven fold higher level of endogenous IAA was recorded for cv K.Sutlej over cv K.Giriraj. As a result, perhaps there was a callusing response from the cut end of the internodal explants of both the cvs in the MS basal medium. The extent of callusing was relatively higher in cv K.Sutlej when compared to that in K.Giriraj. The callusing response was inhibitory to shoot morphogenesis. Inclusion of an established anti-auxin, 2,3,5-tri-iodobenzoic acid (TIBA) in the regeneration medium facilitated a high frequency adventitious shoot regeneration response with lower cytokinin levels. Murashige and Skoog (MS) medium containing TIBA at 2.5 mg l−1 and 0.25 mg l−1 zeatin evoked a 100% regeneration response (4.5 shoot buds per explant) in cv K.Sutlej within 20–25 days. However, in cv K.Giriraj, which had lower levels of endogenous IAA, 80% regeneration response (1.4 shoot buds per explant) was recorded in an extended period of 40–45 days on a medium containing 0.5 mg l−1 TIBA and 0.1 mg l−1 zeatin. Although, TIBA and zeatin induced shoot bud formation, it failed to support sustained growth of the regenerated shoots in cv K.Giriraj. Hence, 0.01 mg l−1 α-naphthaleneacetic acid (NAA) with a relatively higher concentration of zeatin (1.0 mg l−1) were used for sustained shoot regeneration (3.3 shoot buds per explant) within 25 days. From our results, it is evident that there was a difference in the requirement of exogenous zeatin levels required to induce a regeneration response in two cultivars of potato and this is attributed to the variable levels of endogenous IAA.

English

Multiple frequently interactive stress factors naturally influence plant due to global change. The leaf’s hormone concentrations, main-stem and branch yield response to the combination of shade and drought were studied in a greenhouse experiment during 2009 and 2010 seasons. Pot experiments were conducted under shade of maize (LI) and normal irradiance (HI). Shade stress was removed once maize was harvested. Manipulative progressive soil drying period at branching stages under good soil conditions (HW) and water stress treatment (LW) were applied in 2010, while well-watered (WW) and moderate drought (MD) were applied in 2009. Under shade stress, seedling height and first internode length increased, stem diameter decreased, abscisic acid (ABA) and zeatin (ZT) concentration decreased, while indole acetic acid (IAA) and gibberellins 3 (GA3) concentration increased. More also, branch numbers, pod number of branches and seed number of branches increased. Branch yield did not reduce significantly under shade stress, which was related to the decrease of ABA and IAA. Based on the results, soybean yield decreased under shade and drought stresses was mainly due to the yield reduction of the main-stem.

Competitive-IgY- Enzyme Linked Immuno Sorbent Assay (CIgY-ELISA) to detect the cytokinins in Gerbera jamesonii plantlets

A competitive hyper-immune yolk Immunoglobulin Y - Enzyme Linked Immune Sorbent Assay (CIgY-ELISA), was developed as an alternative method to detect zeatin and 2ip in plantlets of gerbera. The endogenous level of hormones in the plantlets in vitro of gerbera with one or six weeks after replication was determined with competitive IgY-ELISA set to detect between 1 and 100 pmoles of plant hormone for each 1.0 g tissue. The plantlets of six weeks presented sprouts and root, while the plantlets of one week presented only sprouts. The CIgY-ELISA was set with high independent variables values of sensitivity/specificity of 96/89 % for zeatin and 94/78 % for 2ip, with high values of reproducibility (up to 90 %) for both the cytokinins. Zeatin content varied from 2.2 to 2.8 pmoles.g-1 and from 2.7 to 3.3 pmoles.g-1 on the plantlet with one and six weeks, respectively. The 2ip content did not vary and was detected near the detection limit in all the assays. It was concluded that the observed capabilities of CIgY-ELISA were putative and the competitive assay was a highly robust and stable method, which could be used for the studies on plant physiology for endogenous cytokinins.

Direct shoot regeneration from leaf explants of Digitalis lamarckii, an endemic medicinal species

This study reports, for the first time, an efficient in vitro plant regeneration protocol for Digitalis lamarckii Ivan. (dwarf foxglove) via direct shoot organogenesis. Two sets of experiments were carried out; the first compared different concentrations of 6-benzylaminopurine (BAP), kinetin, thidiazuron (TDZ), and zeatin alone using leaf explants excised from in vitro germinated seedlings, while the second set tested the combinations of indole-3-butyric acid (IBA) with BAP, kinetin, TDZ, and zeatin for shoot multiplication from the leaf explants, which were already cultured and developed numerous shoots during the first set of experiments. For shoot regeneration (the first set of experiments), TDZ was the most effective at 1.0 mg L^{-1} concentration, producing a mean of 10.3 shoots per explant and was significantly more effective than BAP. For shoot multiplication (the second set of experiments), a combination of 0.2 mg L^{-1} IBA with 0.2 mg L^{-1} TDZ produced significantly more shoots per explant (16.5 shoots) than with BAP (11.0 shoots), zeatin (5.5 shoots), or kinetin (4.0 shoots). The regenerated shoots were readily rooted on medium containing 0.5 mg L^{-1} indole-3-acetic acid (IAA). Rooted regenerants were then transferred to the pots, where they grew well and attained maturity. The described protocol provides a simple way to regenerate plants through direct shoot organogenesis, which would be useful for a large-scale production of cardenolides, germplasm conservation, and genetic transformation studies in this medicinally important endemic species.

Loss of flower bud vigour in the Mediterranean shrub, Cistus albidus L. at advanced developmental stages

To better understand aging in perennials, age-related changes in the physiology of leaves and flower buds of the Mediterranean shrub, Cistus albidus L. were evaluated. Two groups of different ages (5 and 10 years old), both at advanced developmental stages but of similar size, were compared. Total plant biomass, biomass produced per apical meristem and levels of cytokinins, abscisic acid and jasmonic acid in leaves and flower buds, as well as flower production, were measured. No differences in plant size, vegetative growth rates and levels of phytohormones in leaves were observed between 5- and 10-year-old plants. However, they showed significant differences in flower bud development; the older plants having reduced vigour, with 29.6% of flowers reaching anthesis compared to 52.5% in the younger plants. Furthermore, endogenous concentrations of zeatin and abscisic acid in flower buds at stage I (start of flower organ formation) were 61% and 41%, respectively, smaller in 10- than in 5-year-old plants. At stage II (with all flower organs formed), zeatin and abscisic acid concentrations decreased by ca. 90% and 80%, respectively, but differences between age groups were still evident (60% and 29% for zeatin and abscisic acid, respectively). Jasmonic acid levels in flower buds decreased by 80% from stage I to II, but did not differ between age groups. Despite reductions in flower bud vigour, total number of flowers per individual was not significantly different between age groups, so that an age-related loss in reproductive vigour at the organ level did not lead to a decrease in flower production at the whole plant level.

The effect of nitrogen and phosphorus fertilization on yield, some fruit characteristics, hormone concentrations, and alternate bearing in pistachio

This research was carried out in order to determine the effects of nitrogen and phosphorus fertilization on yield, some fruit characteristics, hormone concentrations, and alternate bearing in pistachio (Pistacia vera L.) cv. 'Kırmızı' grafted on P. vera over 3 consecutive years. Nitrogen was applied at the rate of 0 (control), 800, 1000, and 1200 g tree^{-1}, and phosphorus was applied at the rate of 0 (control), 200, 400, and 600 g tree^{-1} into the soil. As a result, although yield mostly decreased and nut weight increased, especially in the 2^{nd} year ('off' year), considerable interactions among fertilizer rates were determined for only nut weight, auxin, gibberellic acid, and zeatin concentrations (P Keywords: Alternate bearing, fertilization, GA3, IAA, nut weight, Pistacia vera L.

The effects of heavy metal salts on the phytohormonal status and sex expression in marijuana

We studied the effects of heavy metal salts (Pb(NO3)2, CuSO4, and ZnSO4) on phytohormonal status and sex expression in various cultivars of marijuana (Cannabis sativa L.), a dioecious plant, grown on Knop nutrient medium. Pb(NO3)2 and ZnSO4 were added to the medium at the concentration of 10−9 M, and CuSO4, at the concentration of 10−10 M. Plant were grown under controlled conditions at luminescent illumination, 22–24°C, and 80% humidity. The contents of GA and zeatin were determined by HPLC. Copper and zinc salts induced plant feminization, and this effect was coupled with zeatin accumulation. Lead salts favored plant masculinization coupled with GA accumulation. Thus, a shift in sex expression in marijuana plants was correlated with the heavy metal action on the balance of phytohormones, GA and zeatin.

Effect of different plant growth regulators on micro-tuber induction and plant regeneration of Pinellia ternate (Thunb) Briet

An efficient micropropagation system for Pinellia ternate (Thunb) Briet, a traditional Chinese medicinal plant, has been developed. Petiole and lamina of P. ternate were used as explants and cultured on Murashige and Skoog (MS) medium containing different concentrations of different plant growth regulators. The results indicated that low concentration of 2,4-dicholorophenoxy acetic acid (2,4-D), indole-3-acetic acid (IAA) and α-naphthalene acetic acid (NAA) were suitable for micro-tuber induction, but callus induction rate increased with increasing concentrations of growth regulators. Tubers induction rates of petiole and leaf were (81.8 %-100 %) and (89.4 %-96.0 %) respectively, when 0.2 mg l(-1) 2, 4-dicholorophenoxy acetic acid, indole-3-acetic acid or α-naphthalene acetic acid were present in the medium. Tubers induction rates of petiole and leaf cultured on MS medium supplemented with 0.2-0.5 mg l(-1) 6-benzyl amino purine (6-BAP) were (94.1 %-100 %) and (96.0 %-100 %) respectively. When the concentration of 2,4-dicholorophenoxy acetic acid, α-naphthalene acetic acid and 6-benzyl amino purine was increased to 2.0 mg l(-1), callus induction rates of petiole and leaf were 100 % and 98.2 %, 91.0 % and 36.0 %, 62.3 % and 70.0 %, respectively. Different concentration of kinetin (KT) and zeatin (ZT) had no significant effect on micro-tuber induction of petiole. Most petioles showed polarity during the cultivation of explants, when supplemented with different concentrations of auxin or cytokinin in the MS medium.

A simple and efficient Agrobacterium-mediated procedure for transformation of tomato

We describe a highly efficient and reproducible Agrobacterium-mediated transformation protocol applicable to several varieties of tomato (Solanum lycopersicum, earlier known as Lycopersicum esculentum). Conditions such as co-cultivation period, bacterial concentration, concentration of benzyl amino purine (BAP), zeatin and indole acetic acid (IAA) were optimized. Co-cultivation of explants with a bacterial concentration of 108 cells/ml for three days on 2 mg/l BAP, followed by regeneration on a medium containing 1 mg/ml zeatin resulted in a transformation frequency of 41.4%. Transformation of tomato plants was confirmed by Southern blot analysis and beta-glucuronidase (GUS) assay. The protocol developed showed very high efficiency of transformation for tomato varieties Pusa Ruby, Arka Vikas and Sioux. The optimized transformation procedure is simple, efficient and does not require tobacco, Petunia, tomato suspension feeder layer or acetosyringone.

할미 꽃 (Pulsatilla koreana NAKAI) 식물 절편체로부터 부정아 유도에 미치는 cytokinin의 영향 및 식물체 재 분화

Leaf and petiole explants of Pulsatilla koreana NAKAI were cultured on MS medium supplemented with various concentrations of zeatin, kinetin or BAP combined with 0.05 mg/L IAA. After 6 weeks of culture, effects of cytokinin on adventitious shoot formation from explants were investigated. The highest frequency of shoot formation was obtained when petiole explants were cultured on medium with 0.5 mg/L zeatin and 0.05 mg/L IAA. Regenerated shoot were transferred on to root induction medium. The best root formation was observed at 1/2 MS medium with 1.5 mg/L NAA. Rooted plantlets were transplanted to a mixture of perlit and soil (1:3), where they were successfully acclimatized.

Relationship between plant hormone level excreted by ectomycorrhizal fungi and growth of poplar NL-895

To explore the effects of plant hormones levels excreted by ectomycorrhizal (ECM) fungi on the growth of poplars, Populus × euramericana cv. NL-895 seedlings were inoculated with nine species of ECM fungi. We investigated the status of ectomycorrhizal formation and the effects of these fungi on poplar growth, and using the HPLC method, we measured the contents of four kinds of plant hormones, indole acetic acid (IAA), zeatin (Z), gibberellin (GA) and abscisic acid (ABA) in both the culture filtrate and the mycelium of these fungi. The results showed that the effects of nine ECM fungi on the growth of poplar NL-895 varied. The inoculated seedlings, whether or not obvious mycorrhizas were developed, grew better than those non-inoculated ones. All nine ectomycorrhizal fungi excreted the four plant hormones, but at different levels. The hormone contents in culture filtrate were higher than that in mycelium, which showed a definite relationship with poplar growth. Significantly, correlation analysis suggested the height and stem diameter of the poplar were positively correlated with zeatin contents in the mycelium, and were negatively correlated with the levels of ABA or IAA in the mycelium.

Low level expression of prokaryotic tzs gene enhances growth performance of transgenic poplars

We modulated the level of a hormone gene expression in poplars using either 35S promoter (p35S) of cauliflower mosaic virus (CaMV) or aux promoter (pAUX) of A. rhizogenes. The transgenic poplars (Populus alba × P.tremula var. glandulosa), in which the bacterial trans-zeatin secretion (tzs) gene was attached either to the 35S promoter or to the aux promoter, were compared for their performance in tissue culture as well as in nursery. Northern blot analysis of total RNA probed with tzs coding region showed that the total tzs mRNA expression by p35S was approximately 200–300-fold higher than that driven by pAUX. In contrast, the cellular zeatin content of p35S-tzs transgenic poplars was merely 13-fold of those found in pAUX-tzs plants. Due to different levels of cellular zeatin levels, the two types of transgenic poplars showed different morphogenetic as well as growth responses. The p35S-tzs transgenic plants showed morphological characteristics typical of those treated with cytokinin in culture. These include multiple axillary shoot formation, thick stems, narrow leaves and absence of roots. In contrast, the pAUX-tzs plants had slightly higher cellular cytokinin levels than did control plants and showed a lower degree of cytokinin-related phenotypes, including a few axillary shoots in root-inducing media. Since p35S-tzs did not develop roots, only pAUX-tzs transgenic poplars could be transplanted to the nursery where they resumed a close-to-normal growth. Nevertheless, pAUX-tzs plants transferred to the nursery developed cytokinin-related phenotypes, including greater number of shoots, smaller leaves and slightly retarded growth in height, but with a high total biomass.