Plant Growth Regulator Treatments Research Articles

Induction, characterization, and NMR-based metabolic profiling of adventitious root cultures from leaf explants of Gynura procumbens

Gynura procumbens is a medicinal plant used in South East Asia to treat various ailments such as rash, hemorrhoids, inflammation, and diabetes. In order to develop a large-scale culture system for G. procumbens biomass containing bioactive compounds, adventitious root cultures were initiated from leaf explants. Murashige and Skoog (MS) media containing different compositions of indole-3-butyric acid (IBA), 1-naphthalene-acetic acid (NAA), and combinations of both plant growth regulators (PGRs) were evaluated for root induction. A combination of 3 mg/l NAA + 1 mg/l IBA gave the highest root induction (48%) as compared to other PGRs treatments after 9 weeks of incubation period. Subsequently, the adventitious roots were established in liquid culture containing MS medium and the combination of 3 mg/l NAA + 1 mg/l IBA. A study on the medium strength, sucrose concentration, pH, and light versus dark was conducted to optimize the in vitro culture conditions. The results showed that differences in MS medium strength from half to double strength, and light or dark condition did not significantly affect the biomass production, while the initial medium pH of 5.5 and 2% w/v sucrose concentration were most suitable for the root culture growth. Nuclear magnetic resonance (NMR) spectroscopy was performed to characterize the metabolite content in the root cultures of G. procumbens. Among the elucidated metabolites were some phenylpropanoids identified as caffeic acid, chlorogenic acid, and 3,5-di-O-caffeoylquinic acid which might be the bioactive compounds associated to the folk use of this plant.

Applications of Plant Growth Regulators to Container-grown Citrus Trees Affect the Biology and Behavior of the Asian Citrus Psyllid

Asian citrus psyllid [ACP (Diaphorina citri)] is an important pest of citrus (Citrus sp.) in many citrus-growing regions of the world because of its status as the vector of huanglongbing disease [HLB (citrus greening)]. There are currently no HLB-resistant citrus genotypes and no proven treatments for the disease; thus, vector control through the use of frequent prophylactic pesticide applications is key to managing the spread of this disease. However, this practice is unsustainable and other means of altering ACP biology or reducing populations are needed. To this end, six plant growth regulators (PGRs) were tested to determine their effect on citrus tree vegetative growth and the subsequent impact on the biology of ACP. In greenhouse and growth chamber experiments, ACP reared on trees treated with prohexadione calcium and mefluidide exhibited significant reductions in both fecundity and survivorship, whereas uniconazole affected only fecundity and paclobutrazol affected only survivorship. No significant effects of PGRs on adult ACP weight were observed except on uniconazole-treated trees. No eggs were laid on dikegulac sodium-treated trees; however, this was likely the result of severe phytotoxicity rather than a true PGR effect. Oviposition rate was lower on all the PGR-treated trees, except chlormequat chloride under greenhouse conditions, compared with untreated control trees. In general, oviposition was delayed on PGR-treated trees compared with untreated controls. The observed changes in ACP biology and behavior after PGR treatment were not the result of a reduction in the number of suitable oviposition sites (i.e., growth reduction) or toxicity of the PGRs to ACP, suggesting there were PGR-induced plant biochemical changes that altered host plant quality. Leaf nutrient analyses and photosynthesis indicated that there were no correlative changes in plant nutrient status or carbon assimilation that led to the changes in ACP behavior, although it is possible that phloem-specific nutrient or carbohydrate changes could have occurred that were not detected in our whole-leaf analyses. These results support previous studies in which the fitness of various insect species has been affected by PGR applications, but more research is needed to understand the changes in plant chemistry that are responsible.

Effects of growth regulators and activated charcoal on in vitro bulblet multiplication and growth in Galanthus nivalis ‘Flore Pleno’

SummaryThe in vitro multiplication of Galanthus nivalis ‘Flore Pleno’ bulblet clumps was evaluated through three 16-week sub-culture passages on media supplemented with either 1.0 mg l–1 6-benzylaminopurine (BA) and 0.1 mg l–1 naphthaleneacetic acid [NAA; the plant growth regulator (PGR) control], 0.5 mg l–1 BA and 0.05 mg l–1 NAA (PGR/2), or 0.1 mg l–1 BA and 0.01 mg l–1 NAA (PGR/10). At the end of the second sub-culture passage, clumps of bulblets from each of the three PGR treatments were also transferred to conditions to promote bulblet growth (G medium without PGRs) supplemented with 60 g l–1 sucrose and 5 g l–1 activated charcoal (AC). Lowering the PGR concentration during the initial multiplication phase reduced bulblet multiplication and overall culture growth, but did not influence bulblet size, as indicated by the diameter of the largest bulblet. Lowering the PGR concentration during the multiplication phase also reduced the multiplication of bulblets, overall tissue fresh weight, and the production of roots in tissues transferred to bulblet growth conditions. The reduced growth of tissues previously multiplied on PGR/10 medium was not, however, reflected in the growth of individual bulblets, since these were not significantly smaller than bulblets initially multiplied at the higher PGR concentrations. Bulblet sprouting and root growth on the bulblet growth medium were unaffected by prior PGR status in the multiplication phase. The results are discussed in terms of the mode of action of AC on the promotion of bulblet growth.

Erratum to: Levels of endogenous abscisic acid and indole-3-acetic acid influence shoot organogenesis in callus cultures of rice subjected to osmotic stress

Osmotic stress and endogenous hormone levels may have a role in shoot organogenesis, but a systematic study has not yet to investigate the links. We evaluated the changes of the endogenous indole-3-acetic acid (IAA) and abscisic acid (ABA) levels in rice (Oryza sativa L. cv. Tainan 5) callus during shoot organogenesis induced by exogenous plant growth regulator treatments or under osmotic stress. Non-regenerable callus showed low levels of endogenous ABA and IAA, with no fluctuation in level during the period evaluated. The addition of 100 μM ABA or 2 mM anthranilic acid (IAA precursor) into Murashige and Skoog basal induction medium containing 10 μM 2,4-D enhanced the regeneration frequency slightly, to 5 and 35%, respectively, and their total cellular ABA or IAA levels were increased significantly, correspondingly to the treatments. However, the regeneration frequency was greatly increased to 80% after treatment with 0.6 M sorbitol or 100 μM ABA and 2 mM anthranilic acid combined. Both treatments produced high levels of total cellular ABA and IAA at the callus stage, which was quickly decreased on the first day after transfer to regeneration medium. Thus, osmotic stress-induced simultaneous accumulation of endogenous ABA and IAA is involved in shoot regeneration in rice callus.

Metabolic evaluation of cellular differentiation of tobacco leaf explants in response to plant growth regulators in tissue cultures using 1H NMR spectroscopy and multivariate analysis

To investigate the metabolic changes that precede visible organogenesis in tissue culture, tobacco leaf explants were cultured on media supplemented with various plant growth regulators (PGRs) and analyzed with proton nuclear magnetic resonance (1H NMR) spectroscopy. Principal component analysis (PCA) of 1H NMR spectral data was unable to differentiate between leaf explants cultured with α-naphthaleneacetic acid and those cultured with 6-benzyladenine after 4 days of culture; however, a difference was evident after 8 days of culture. A hierarchical dendrogram from PCA analysis could be grouping leaf explants cultured with various auxins separately from those treated by various cytokinins. However, leaf explants cultured with thidiazuron (TDZ) were identified as an outlier group; TDZ appeared to produce pleiotropic metabolic effects that differed from those induced by other PGRs. These results show that dedifferentiation can be initiated by either auxins or cytokinins, which is reflected by similar metabolic changes produced by the two distinct PGRs during the initial incubation period. The subsequent redifferentiation differs according to the PGR treatment, which is reflected by differential metabolic changes, depending on the fate of cells in organogenesis. Glutamine and glutamate levels increased approximately twofold in cytokinin-treated leaf explants compared with auxin-treated explants; however, changes in the levels of sugar compounds did not differ between the two treatments, demonstrating auxin regulation of the carbon/nitrogen ratio in favor of rooting. Taken together, our results suggest that 1H-NMR spectroscopy combined with multivariate analysis is a promising means for the metabolic evaluation of plant growth and differentiation.

An Assessment of Plant Growth Regulators on Asymbiotic Cevelopment and Germination of Immature Embryos of Beclardia macrostachya (Orchidaceae)

Beclardia macrostachya is one of the rarest orchids in Mauritius. In vitro techniques are being used for mass propagation of this orchid for subsequent restoration programs. Successful asymbiotic germination of Beclardia macrostachya was obtained through embryo rescue under in vitro conditions. Modified half MS medium supplemented with 10% coconut milk was used as basal culture medium and the effect of plant growth regulators at different concentrations on embryo development was assessed through qualitative and quantitative parameters. Diameter of embryos, length of protocorm-like bodies (PLBs) and length of developing shoots were calculated using digital photography. Maximal growth was obtained in treatments without any plant growth regulators and with 0.5 mg/L N6-Benzylaminopurine (BAP). Higher levels of Thidiazuron/TDZ (0.3 mg/L) and BAP (1.0 mg/L) though they stimulated embryo development faster, yielded higher level of necrosis later. The results also suggest that plant growth regulator treatments that stimulate fastest embryo development from immature embryos/ovules need not be reliable for further development to PLB and plantlet regeneration.

Plant growth regulator treatments for a tissue culture of Euodia rutaecarpa

To determine the effects of different plant growth regulator treatments，including 6-benzylaminopurine （6-BA），1-naphthlcetic acid （NAA），2，4-dichlorophenoxy acetic acid （2，4-D），and N-phenyl-N-1，2， 3-thidiazol-5-yl-urea（TDZ），on various processes of tissue culture in female plants of Euodia rutaecarpa （Juss.） Benth，leaves of regenerated shoots were used. Results showed that 1.0 mgL-1 6-BA alone or with 0.1 mgL-1 NAA induced both callus and adventitious buds. The other plant growth regulator treatments induced the formation of callus，but failed to induce adventitious buds. NAA by itself did not induce adventitious buds，but it did promote the effects of 6-BA. As the concentration of 6-BA increased，the rate of bud differentiation first increased and then declined，a similar trend happened with 6-BA on morphogenesis of adventitious buds. With an optimal concentration，6-BA promoted proliferation，whereas a high concentration led to vitrification. Also，0 - 0.1 mgL-1 NAA promoted rooting and roots appeared faster and stouter as NAA increased. Moreover，the survival rate after transplanting increased. However，0.5 mgL-1 NAA inhibited the growth of lateral roots and the transplanting procedure. After transplanting in the field for 1.5 years，the regenerated plants bloomed.［Ch，1 fig. 4 tab. 10 ref.]

Effects of the shoot-cutting method on field propagation in napiergrass (Pennisetum purpureum Schum.)

In this study, the effects of shoot-cutting method on propagation using overwintering napiergrass (Pennisetum purpureum Schum.) buds were examined under soil conditions compared with plant growth regulators (PGRs) that are used as an effective method for increasing adventitious buds of several gramineous crops. To increase adventitious budding, we cut shoots of napiergrass at 2 weeks after planting and treated with the following four types of PGR in comparison with shoot-cutting: 4.44 mM BA as cytokinin, 3.63 mM triazine as anticytokinin, 5.37 mM NAA as auxin, and 2.22 mM TIBA as antiauxin, either by injection or direct spraying onto the buds. A large number of adventitious buds were observed in BA- and TIBA-injected buds at 4 WAT compared to shoot-cut or PGR-sprayed buds. However, an extremely low survival rate for tiller-divided plants (nursery plants) derived from both BA- and TIBA-injected plants was observed compared with non-PGR controls. Similar trends on the survival rate and relative tiller number in main shoot-cut plants derived from intact buds (without PGR treatment) were also observed in a repeat trial. The present study demonstrated that the method of shoot-cutting could contribute to increasing propagation efficiency for nursery plants compared with exogenous PGR application, and would be a practical method for increased nursery propagation of napiergrass under soil conditions.

In vitro seed germination and micropropagation of primrose (Primula heterochroma Stapf.) an endemic endangered Iranian species via shoot tip explants

Primula heterochroma is a scarce and endemic plant to the north of Iran. The aim of the present study is to establish an efficient and reproducible protocol for in vitro propagation from shoot tips. Native seeds were exposed to different treatments. Germination results showed that the scarification of seeds had significant effects on the germination delay and germination percentage compared to plant growth regulator treatments. Afterwards, the seedling-derived shoot tips were cultured on several Murashige and Skoog basal medium, containing various concentrations of 6-benzylaminopurine (BA) or thidiazuron (TDZ) in combination with various concentrations of 1-naphthaleneacetic acid (NAA). The result showed that the highest shoot regeneration, and the number and length of leaves were noticeably affected by media enriched with 1· mg L−l BA + 0.4 mg · L−1 NAA and 0.2 mg · L−1 TDZ + 0.4 mg · L−1 NAA. Root parameters significantly affected by media enriched with 1 mg · L−1 BA + 0.8 mg · L−1 NAA and 0.4 mg · L−1 TDZ + 0.8 mg · L−1 NAA. Plantlets were hardened-off and transferred to soil for further growth.

Effects of plant growth regulator treatments on stem vascular tissue development in linseed ( Linum usitatissimum L.)

Linseed ( Linum usitatissimum L.) is a widely grown source of industrial and edible oil. Other varieties of the same species (flax) are cultivated for the long, strong bast fibres of their stems. The bast fibres of linseed generally go unused, although there is growing interest in developing linseed into a dual-purpose flax from which both seed and fibre could be utilized. Towards this objective, an improved understanding is required of the role of plant growth regulators in stem and fibre development in linseed. We have tested the effects of applying varying combinations of gibberellic acid (GA 3), the auxin indole-3-acetic acid, and a GA biosynthesis inhibitor (paclobutrazol) to an elite linseed variety (CDC Bethune). Results showed that GA stimulated stem elongation, stem expansion and the proliferation, expansion, elongation and cell wall thickening of xylem fibres. The impact of GA on phloem tissues was less apparent, although GA had a positive effect on the number of bast fibres observed in stem transverse section, and GA 3 application in combination with IAA increased the thickness of bast fibre secondary walls nearly two-fold. Other than the bast fibre cell walls, IAA treatments (alone or in combination with GA 3) did not affect most aspects of linseed stem development, suggesting that the observed effects of GA were not mediated by cross-talk with IAA. The relationships defined here between GA, stem architecture, and bast fibre properties in linseed provide a useful framework for manipulation of fibre properties through breeding, biotechnology, and field treatments.

Endogenous indole-3-acetic acid and trans-zeatin ribosides in relation to axillary bud formation in standard chrysanthemum

The lateral buds of non-branching chrysanthemum cultivars are affected by temperature and exogenous plant growth regulator (PGR) treatment. The number of axillary buds, endogenous indole-3-acetic acid (IAA) and t-zeatin riboside (t-ZR) concentrations by planting date and PGR treatments were investigated in three genotypes. Two non-branching genotypes, ‘Iwanohakusen’ and ‘01B1-8’ and branching type ‘Jinba’ were planted on May 2 and June 29. ‘Jinba’ always bore axillary buds and ‘01B1-8’ showed stronger non-branching traits than ‘Iwanohakusen’. Only 22.9% viable buds developed in the axils of ‘01B1-8’ whereas 68.7% developed in ‘Iwanohakusen’ on the May 2 planting date group. When planting was delayed from May 2 to June 29, the number of axillary buds decreased in both non-branching genotypes. Endogenous IAA concentrations remained unchanged and t-ZR concentrations decreased in all the three genotypes when the planting date was delayed. This reduced t-ZR level corresponds to the increased ratio of IAA/t-ZR. The number of viable axillary buds increased from 21.7% to 50.1% upon ethephon treatment and to 30.3% by synthetic cytokinin 6-benzylaminopurine (BAP) treatment in ‘01B1-8’. Viable axillary buds of ‘01B1-22’ increased from 17.1% to 25.1% and 29.1% respectively. Ethephon and BAP application decreased endogenous IAA contents and increased t-ZR contents. Elevated concentrations of t-ZR rather than IAA probably account for axillary bud formation in non-branching chrysanthemum. Just as the non-branching genotypes, the branching type cultivar ‘Jinba’ showed similar changes in IAA and t-ZR contents according to planting date and exogenous PGR treatments. These results showed that genotypic difference of branching patterns is not a result of concentration-dependent reaction.

Establishment and characterization of Prosopis laevigata (Humb. & Bonpl. ex Willd) M.C. Johnst. cell suspension culture: a biotechnology approach for mesquite gum production

This study presents a protocol for the establishment of Prosopis laevigata cell suspension culture as a strategy to obtain an in vitro mesquite gum productive cell line. The callus used for this purpose was obtained with hypocotyls from 15-day-old plantlets, placed on Murashige–Skoog medium with two different plant growth regulators (PGRs), 2,4,5-trichlorophenoxy acetic acid (2,4,5-T; 5.0 μM) and kinetin (KIN; 5.0 μM). With this PGRs treatment, after four subcultures (30 days each) an exuded gum-like substance was observed on the callus surface. The growth kinetics of the cell suspension culture showed a specific cell growth rate (μ) of 0.14 d−1 and doubling time (t d) of 6.6 days, respectively. The gum-like substance from callus culture and the broth from cell suspension culture were subjected to chemical analysis and compared with the mesquite gum exuded from wild trees. Both, gum-like substance from callus culture and the broth from cell suspension culture showed the presence of Arabinogalactan-proteins, and their polysaccharide fraction presented the same monosaccharides as those isolated from mesquite gum. In addition, the emulsifying properties of gum-like substance from callus culture and the broth from cell suspension culture were compared to those of mesquite gum and all three samples exhibited similar emulsifying capacity and emulsification stability.

Effects of calliterpenone and GA3 on the growth, yield, and pyrethrin contents of pyrethrum [Tanacetum cinerariifolium (Trevir.) Sch. Bip.] planted on different dates

SummaryStudies on the effects of calliterpenone and gibberellic acid (GA3) on the growth, yield, and pyrethrin contents of pyrethrum [Tanacetum cinerariifolium (Trevir.) Sch. Bip.] planted on three separate dates at Lucknow, India indicated that plant height, the number of shoots per plant, the percentage of flowering plants, the number of flowers per plant, and the pyrethrin contents of flowers declined significantly with a delay in planting. Pyrethrum seedlings planted on 3 November, without any plant growth regulator (PGR) treatment, produced the highest dry weight (DW) of flowers and the greatest yield of pyrethrins (159.5 kg ha–1). Delays in planting to 23 November or 13 December caused 34% and 42% reductions in flower DWs, and 48.5% and 73.1% reductions in pyrethrin yields, respectively, compared to the 3 November planting. Two sprays of either PGR, at 60 d and 75 d after planting (DAP), resulted in significant reductions in floral DWs and in the yield of pyrethrins in pyrethrums planted on 3 November. However, spraying with 3.2 mg l–1 calliterpinone resulted in 21.2% and 24.1% increases in flower yields in the 23 November and 13 December plantings, respectively, compared to the non-sprayed controls. Spraying with 3.2 mg l–1 calliterpenone resulted in a significant increase in pyrethrin contents in the 3 November planting, but reduced pyrethrin contents in the later (3 December) crop. Spraying with 0.32 mg l–1 calliterpenone resulted in significantly higher concentrations of pyrethrins [0.28% (w/w) and 0.24% (w/w), respectively] in the 23 November and 13 December plantings. Spraying 3.2 mg l–1 calliterpenone on the 23 November plantings, and 0.32 mg l–1 calliterpenone on the 13 December plantings resulted in significantly higher yields of pyrethrins (107.6 and 79.7 kg ha–1, respectively) compared to the non-sprayed controls. Planting pyrethrum seedlings during the first week of November is normally recommended to obtain maximum flowering and pyrethrin yields under the sub-tropical climatic conditions of the northern Indian plains. Alternatively, spraying pyrethrum seedlings planted on 23 November or on 13 December twice with calliterpenone at 3.2 mg l–1 or 0.32 mg l–1, respectively, at an interval of 10 – 12 d starting 60 DAP can also be recommended to achieve higher yields of pyrethrins.

Expression of SbGSTU (tau class glutathione S-transferase) gene isolated from Salicornia brachiata in tobacco for salt tolerance

Tau class glutathione transferases (GSTU) genes are plant specific, induced by different abiotic stress, and important for protecting plants against oxidative damage. GST gene was isolated using 5' RACE from an extreme halophyte Salicornia brachiata, cloned, sequenced and its protein structure was predicted. Transcript profiling of SbGST gene expression was studied under different abiotic stress conditions and plant growth regulator treatments, viz. salt, cold, drought, ABA and salicylic acid, with time period point and concentration point. The expression of SbGST gene was up-regulated in all stress conditions, except SA treatment. Seed germination percentage, GST enzyme assay, fresh weight and other growth parameters (root length, shoot length and leaf area) were studied and results indicate that over-expression of SbGST gene in transgenic tobacco leads to enhanced seed germination and growth under salt stress. Transgenic lines were evaluated for their performance under salt stress and tobacco plants over-expressing SbGST showed higher seed germination and survival compared to wild type. These results confirm that expression of SbGST gene is up-regulated by different stresses and over-expression of tau class SbGST gene in transgenic tobacco plays a vital role in abiotic stress tolerance. SbGST gene expressed conspicuously under salt stress leading to enhance seed germination and better growth. Furthermore, GST is a potential candidate gene to be used in genetic engineering for enhancing abiotic stress tolerance.

Rapid burst of H 2O 2 by plant growth regulators increases intracellular Ca 2+ amounts and modulates CD4 + T cell activation

The identification of small molecules that affect T cell activation is an important area of research. Three molecules that regulate plant growth and differentiation, but not their structurally similar analogs, were identified to enhance primary mouse CD4 + T cell activation in conjunction with soluble anti-CD3 stimulation: Indoleacetic acid (natural plant auxin), 1-Napthaleneacetic acid (synthetic plant auxin) and 2,4-Dichlorophenoxyacetic acid (synthetic plant auxin and herbicide). These effects are distinct in comparison to Curcumin, the well known phenolic immunomodulator, which lowers T cell activation. An investigation into the mechanisms of action of the three plant growth regulators revealed a rapid induction of reactive oxygen species (ROS), mainly comprising H 2O 2. In addition, these three molecules synergize with soluble anti-CD3 signaling to enhance intracellular Ca 2+ concentrations [Ca 2+] i, leading to greater T cell activation, e.g. induction of CD25 and IL-2. Enhanced production of TNFα and IFNγ by CD4 + T cells is also observed upon plant growth regulator treatment with soluble anti-CD3. Interestingly, maximal IL-2 production and CD4 + T cell cycle progression are observed upon activation with soluble anti-CD3 and phorbol 12-myristate 13-acetate (PMA), a phorbol ester. Additionally, stimulation with PMA and Ionomcyin (a Ca 2+ ionophore), which activates T cells by circumventing the TCR, and plant growth regulators also demonstrated the role of the strength of signal (SOS): T cell cycle progression is enhanced with gentle activation conditions but decreased with strong activation conditions. This study demonstrates the direct effects of three plant growth regulators on CD4 + T cell activation and cycling.

In vitro micro-tuber initiation and dormancy in yam

Dormancy is a mechanism that regulates the timing of sprouting (germination) of affected plant parts as well as ensures that the food quality of edible parts is maintained in storage until the following growing season. In yam, however, little is known about the control of tuber initiation or tuber dormancy. The objective of this study was to determine the effects of selected plant growth regulators (PGRs) on tuber initiation and dormancy, using an in vitro system. In two replicated experiments, 2-chloroethylphosphonic acid (ethephon, an ethylene source), abscisic acid (ABA) and gibberellin (GA3) – and their inhibitors silver nitrate, fluridone and 2-chloroethyl-trimethylammonium chloride, respectively – were added at two concentrations to the culture medium prior to explant culture. Dates of micro-tuber initiation and sprouting (end of dormancy) and tuber number were recorded. In the control (no PGR) in Experiment 1, micro-tubers were initiated at the base of the stem after 176 days and sprouted 235 days later, that is 411 days after culturing. Most PGR treatments had only small effects (±30 days) on the duration of dormancy and the time of micro-tuber initiation. However, in GA3 micro-tuber initiation occurred after 76 days, about 100 days earlier than in the control, whereas fluridone affected the position of micro-tubers and duration of dormancy. With fluridone treatments, tubers were found at the base of the stem (normal position) and on lower and upper nodes. Lower node tubers sprouted within 225 days of culturing compared with about 420 days after culturing at other nodal positions and in other PGR treatments. These data suggest an important role for ABA and gibberellic acid in yam micro-tuber initiation and the induction of dormancy.

Produtividade e qualidade tecnológica da soqueira de cana-de-açúcar submetida à aplicação de biorregulador e fertilizantes líquidos

O presente trabalho objetivou avaliar a aplicação de biorreguladores, associados ou não a fertilizantes líquidos, na rebrota e na produtividade da soqueira de cinco genótipos de cana-de-açúcar. O experimento foi desenvolvido no Município de Jaú, São Paulo (SP), num Latossolo Vermelho Eutroférrico. Utilizou-se o delineamento em blocos inteiramente casualizados, em esquema fatorial 5x5, constituído por cinco genótipos (IAC87-3396, IAC91-2218, IAC91-4216, IAC91-5155 e IACSP93-6006) e cinco tratamentos com biorreguladores, associados ou não a fertilizantes líquidos (Stimulate® a 0,5L ha-1; Stimulate® a 0,5L ha-1 + Starter N® a 3,0L ha-1; Stimulate® a 0,5L ha-1 + Starter N® a 3,0L ha-1 + Cellerate® a 0,5L ha-1; Etefon a 3,0L ha-1 e Testemunha), com quatro repetições. A aplicação dos produtos ocorreu 70 dias após a quarta colheita. Foram avaliados: perfilhamento, produtividade de colmos industrializáveis e de açúcar, fibra, pol % cana e açúcar total recuperável. O etefon proporcionou melhor perfilhamento, mas a resposta foi dependente do genótipo. O maior número de perfilhos promovido pelo etefon não refletiu em maior produtividade. A aplicação de Stimulate® e fertilizantes líquidos não proporcionou efeitos na qualidade da cana-de-açúcar. Houve aumento da produtividade de colmos e de açúcar, independente do genótipo, com o emprego do biorregulador Stimulate®, com ou sem complementação de fertilizante líquido, indicando a possibilidade do aumento da longevidade da cana-de-açúcar.

Effect of pre-germination treatments on seed physiology and germination of central Himalayan oaks?

The continuous decline in regeneration of two important species of central Himalayan oak, namely Quercus glauca and Q. leucotrichophora, is of great concern. A study was therefore, carried out to improve germination ability of these species using various presoaking treatments. Seeds of both the species lost viability following storage; tetrazolium staining pattern and germination capacity of seeds following different period of storage at 4 °C and 20 °C indicated retainment of viability for a period of 12 months at 4 °C. Of the various physical, chemical and plant growth regulator treatments examined to improve seed germination, only KNO3 1.0 % was found to be effective. Seeds scarified at the chalazal end exhibited significant improvement in germination in both the species (94.4 % compared to 56.7 % in control in Q. glauca and 82.7 % compared to 64.0 % in control in Q. leucotrichophora). The results of this study impart simple methods to improve seed germination for developing nurseries for commercial purposes.

Seed Germination of Huagaimu, a Critically Endangered Plant Endemic to Southeastern Yunnan, China

As a critically endangered tree in the Magnoliaceae family, huagaimu (Manglietiastrum sinicum) is represented by only 10 mature individuals in evergreen broadleaved montane forests of southeastern Yunnan Province, China. Our previous work revealed the existence of a seed dormancy period for this species. The current study was performed to evaluate the effects of plant growth regulators (PGRs) and moist chilling on breaking seed dormancy in this species. Germination of seeds pretreated for 24 h with gibberellic acid (GA3), α-naphthaleneacetic acid, 6-benzyladenine, and 2,4-dichlorophenoxyacetic acid indicated that only GA3, at concentrations of 300 and 500 mg·L−1, can significantly break the seed dormancy of huagaimu after 50 days of incubation, with about 66% germination under 500 mg·L−1 GA3. Moist chilling at 4 °C for 3 weeks can also effectively break the seed dormancy of the species, with 56% of seeds treated in this way germinating after 30 days of incubation. The combined treatments of PGRs followed by moist chilling were also conducted. Based on germination results after 30 days of incubation, the seed germination of combined treatments was significantly higher than that of PGR treatments. However, the seeds treated only with moist chilling presented the highest germination percentage among all the treatments.

Callus induction, biomass growth, and plant regeneration in Digitalis lanata Ehrh.: influence of plant growth regulators and carbohydrates

The effect of plant growth regulators (PGRs) and carbohydrate sources on callus induction, callus growth, and plant regeneration in foxglove was examined. Explants were transferred onto MS medium with various levels of PGRs and carbohydrates to determine the optimum explant and effective combinations of PGR treatment. For callus induction 6.0 mg L^{-1} of \alpha-naphthalene acetic acid (NAA) and 3.0 mg L^{-1} of benzyl-aminopurine (BA) were very responsive. Addition of cytokinins (BA and kinetin) at 0.5-3.0 mg L^{-1} to media containing NAA enhanced callus growth. Shoot regeneration was best achieved in MS + 6.0 mg L^{-1} of BA. Adenine sulphate (Ade) and casein hydrolysate (Ch) were added to the medium as a nitrogen source to improve plant growth and maximum growth was obtained on medium supplemented with 1.5 mg L^{-1} of kinetin + 0.5 mg L^{-1} of IAA + 500 mg L^{-1} of Ch. Carbohydrates also influenced callus production and shoot regeneration potentiality. Among all the tested carbohydrates (sucrose, maltose, fructose, and glucose) and concentrations (3.0-6.0 g L^{-1}), the optimum carbohydrate concentration was 3.0 g L^{-1} and was applied to all carbohydrate cases.