Influence of paclobutrazol on growth and development of fruit in Brassica juncea (L.) Czern and Coss

Foliar spraying of paclobutrazol(5, 10 and 20 g mL^–1) on Brassica juncea (cv. RLM 514) plants, at the green floral bud stage of the terminal inflorescence, exerted a profound effect on growth and metabolism of fruits (siliquae). Paclobutrazol caused a decrease in siliqua length but enhanced significantly siliqua width, seed size (diameter) and seed number per siliqua. Paclobutrazol increased dry matter production and also hastened the relative growth rate of the siliqua wall and seed. In paclobutrazol-treated plants the siliquae were darker green, and during active phases of growth both siliqua wall and seed exhibited higher total chlorophyll (Chl) content, decreased chl a/b ratios, greater hill reaction activity of chloroplasts and increased activities of -amylase, -amylase and invertase than controls. Paclobutrazol enhanced the levels of total soluble sugars, starch, protein and free amino acids in mature seeds. The seed oil content increased by 2 to 3 per cent with a treatment of 10 g mL^–1 pacolobutrazol.     

Modification of hibiscus growth by treating unrooted cuttings and potted plants with uniconazole or paclobutrazol

Unrooted cuttings ofHibiscus rosasinensis L. Seminole Pink were soaked for 5 s in a solution containing 25, 50, 75, or 100 mg L^–1 uniconazole or paclobutrazol, rooted, and then potted and allowed to grow without pinching. Uniconazole was more effective than paclobutrazol in suppressing stem growth and number and length of lateral shoots. Uniconazole and paclobutrazol, at the 25 mg L^–1 concentration, resulted in stem growth 75 and 25%, respectively, of the control, with further reduction at higher rates. Flowering was delayed by the highest rate of uniconazole but not paclobutrazol. Flower number was reduced by both retardants, without any effect on flower size. Plants treated with uniconazole had short pedicels regardless of the rates, whereas paclobutrazol did not affect pedicel length. A second experiment used unrooted cuttings being soaked in a solution containing 0, 12.5, 25, or 50 mg L^–1 uniconazole or having the lower 2.5 cm of the stem dipped in a solution containing 0, 50, 100, or 200 mg L^–1 uniconazole. Plants were pinched after potting. Soaking resulted in more efficient height control than dipping. Lateral shoot number was reduced by soaking but not dipping. All treated plants had smaller stem diameters. Flower size was unaffected regardless of method of treatment and the type of retardant applied. In a third experiment, soil drenches with uniconazole at a rate as low as 0.05 mg/pot resulted in excessive growth retardation. Soil drenches with paclobutrazol at 0.05–0.20 mg/pot reduced shoot growth, flower number, and pedicel length, but did not affect days to bloom.     

Paclobutrazol enhances minituber production in Norland potatoes

The effect of two plant growth regulators, paclobutrazol and kinetin, on minituber yield in greenhouse-grown Norland potatoes was investigated. Plants were treated with paclobutrazol at 450 mg/L, kinetin at 10 mg/L, or a combination of paclobutrazol at 450 mg/L + kinetin at 10 mg/L as single foliar applications at early stolon initiation. A set of plants sprayed with water served as the control. The experiment was conducted twice. In both cases, paclobutrazol nearly doubled the number of usable tubers/plant without affecting total tuber yield. Kinetin had no effect either on tuber number or tuber weight. Kinetin applied as a combination with paclobutrazol decreased the effectiveness of paclobutrazol on tuber number by 13–20%. Paclobutrazol treatments prolonged tuber dormancy by approximately 3 weeks. The results suggest that paclobutrazol treatment would be effective in enhancing potato minituber production under greenhouse conditions.Abbreviations PTZ paclobutrazol - KIN kinetin     

Testing the “methanochondrion concept”: are nucleotides transported across internal membranes in Methanobacterium thermoautotrophicum?

In order to test the Methanochondrion concept, uptake of adenine nucleotides in various membrane preparations of Methanobacterium thermoautotrophicum was studied. The uptake showed properties which are in general interpreted as indicative of a transport mechanism: (i) kinetics in the time range of minutes, (ii) temperature dependence, (iii) substrate specificity and (iv) failure to remove the substrate by extensive washing.However, nucleotide transport as an interpretation of this uptake can definitely be excluded. Not only an exchange mechanism of the mitochondrial type, but also a general exchange or an uniport mechanism was ruled out. In contrast, the nucleotide uptake was shown to be actually a tight and specific binding of ADP and ATP to binding sites at the interior side of the cell membrane. This was conclusively demonstrated in protoplasts obtained from M. thermoautotrophicum cells. In these protoplasts which do not contain internal membranes also nucleotide binding was observed, but only after disruption of the plasma membrane by osmotic lysis, which leads to the exposure of binding sites.     

Axillary shoot induction and plant regeneration in Plantago ovata Forssk

Axillary shoot induction and plant regeneration were obtained in Plantago ovata. The optimum medium for inducing axillary shoots was Murashige & Skoog (MS) medium [5] supplemented with 4.6 M kinetin and 0.05 M NAA. Rooting of shoots was best on half-strength MS medium containing 5.0 M IBA and 0.05 M kinetin. The regenerated plants were similar to the control plants in karyotypic and phenotypic details.     

Variable increases in cold hardiness induced in winter rape by plant growth regulators

Triazole and conventional growth regulators were tested for their ability to extend cold hardiness and improve the winter survival of winter rape (Brassica napus L.). Winter rape plants were grown in the field (Ottawa 45°23 N) and in growth cabinets. Plant growth regulators (PGRs) were applied during the early vegetative stage and the plants were allowed to cold harden. Cold-hardened plants from the field and cabinet were subjected to freezing and ice encasement tests in the laboratory. Some of the triazole PGRs reduced plant size by limiting cell expansion and increasing cell numbers. While cold hardiness and ice encasement tolerance were increased by some growth regulators, these effects were not consistent with time nor were they reflected in increased winter survival. Natural cold hardening may have eclipsed the PGR-induced hardening.PGR contribution number 1381.     

Sucrose in storage media and cultivar affects post-storage regrowth of <Emphasis Type="Italic">in vitro</Emphasis> Hosta propagules

The goal of this research was to investigate if culturing in high sucrose (5%) liquid media during multiplication phase (stage II) would enhance endogenous sugar levels and dry matter sufficiently to allow storage of in vitro plants in sugar free media without adversely affecting post-storage recovery. Hosta tokudama Newberry Gold (NBG) and Hosta Striptease were cultured in Murashige and Skoog (MS) media containing 5% sucrose during stage II and transferred to rooting phase (stage III) in MS medium without (0%) sucrose or with 3% sucrose for 4weeks. At the end of stage III, cultures were stored, with the remaining media, at 10°C with 5molm^–2s^–1 photosynthetic photon flux (PPF) from cool white fluorescent lamps for 7 or 14weeks with or without a 2-week dark period prior to removal from storage. In both cultivars, stage III plants cultured in 3% sucrose media had higher soluble sugar levels and greater shoot and root biomass than those cultured in 0% sucrose media. Shoot and root soluble sugars decreased during storage. Shoot growth ceased during storage in both media. Root dry matter continued to increase in plants stored in 3% sucrose media but did not change in 0% sucrose media. Plants cultured in 3% sucrose media had less leaf chlorosis and less mortality after 7 or 14weeks of low temperature storage than the plantlets from sugar free media. Extending the storage period from 7 to 14weeks or introduction of 2-week dark period at the end of storage did not affect leaf chlorosis or plant mortality during acclimatization. Post-storage growth varied with the cultivar. Benefit of having sucrose in storage media was to develop a strong root system that aided the acclimatization and post-storage growth following 7 or 14week storage. Sucrose loading by culturing plants in liquid media containing 5% sucrose did not allow storage in sugar free media without adversely affecting post-storage growth in both cultivars.     

Floral bud reversion in Impatiens balsamina under non-inductive photoperiods

Summary All floral buds of Impatiens balsamina plants exposed to 4 short-day (SD) cycles and then returned to long days reverted to vegetative growth. The same happened with the upper buds of plants receiving a larger number of SDs, even as many as 90 cycles. The reversal proceeded in a basipetal order. The number of floral buds and flowers increased, and their reversion to vegetative growth was delayed with increasing numbers of SD cycles. Depending upon the stage attained by the floral bud before the transfer of the plant to noninductive photoperiods one or more inner whorls of the flower were replaced by a vegetative apex. The tip of the placenta was able to resume vegetative growth even after the formation of fertile anthers and an ovary with abortive ovules, showing that the potentiality for reversion is maintained till quite late stages in floral bud development. Continuous exposure to SD cycles is required not only for the continued production of floral buds, but also for their development to mature flowers, indicating that the floral stimulus in this plant is not self-perpetuating.     

Abscisic acid and mefluidide in the regulation of cold hardiness development in Solanum tuberosum L. potato

Plants of Solanum tuberosum L. potato do not cold acclimate when exposed to low temperature such as 5°C, day/night. When ABA (45 M) was added to the culture medium, stem-cultured plantlets of S. tuberosum, cv. Red Pontiac, either grown at 20°C/15°C, day/night, or at 5°C, increased in cold hardiness from –2°C (killing temperature) to –4.5°C. The increase in cold hardiness could be inhibited in both temperature regimes if cycloheximide (70 M) was added to the culture medium at the inception of ABA treatment. Cycloheximide did not inhibit cold hardiness development, however, when it was added to the culture medium 3 days after ABA treatment.When pot-grown plants were foliar sprayed with mefluidide (50 M), ABA content increased from 10 nmol to 30 nmol g^–1 dry weight and plants increased in cold hardiness from –2°C to about –3.5°C. The increases in free ABA and cold hardiness occurred only in plants grown at 20°C/15°C; neither ABA nor cold hardiness increased in plants grown at 5°C.The results suggest that an increase in ABA and a subsequent de novo synthesis of proteins are required for the development of cold hardiness in S. tuberosum regardless of temperature regime, and that the inability to synthesize ABA at low temperature, rather than protein synthesis, appears to be the reason why S. tuberosum does not cold acclimate.     

Influence of paclobutrazol on growth and yield of Brassica carinata A.Br.

Foliar spraying of Brassica carinata (cv. PC 5) with paclobutrazol (PP 333) at 5, 10 and 20 g ml^-1 concentrations, reduced plant height significantly and modified the canopy structure by enhancing the number of branches (primary, secondary and tertiary) and the angle of insertion of primary branches on the main axis. The seed yield per plant also increased mainly due to increase in the number of siliquae per plant. Paclobutrazol increased total dry matter of plants and partitioning coefficients. The leaves in paclobutrazol-treated plants exhibited higher chlorophyll content, and they remained intact on plants for longer than the controls. The seeds from paclobutrazol-treated plants had higher levels of proteins, strarch and total soluble sugars but less total seed oil content.     

Growth and organogenesis in moth bean callus cultures as influenced by triazole growth regulators and gibberellic acid

The triazole plant growth regulators, paclobutrazol and uniconazole, reduced in vitro growth of moth bean callus by 20–25% when added to the culture medium at 1 mg/L (3.4 M). The addition of 10 mg/L (29 M) gibberellic acid (GA₃) to the culture medium in combination with the triazoles restored callus growth to a level equivalent to that of the untreated control. GA₃ alone had little effect on callus growth. When added to a regeneration medium at 1 mg/L both paclobutrazol and uniconazole reduced the percentage of cultures that formed roots, as well as the mean number of roots per culture. In contrast, GA₃ increased root formation and counteracted the inhibitory effects of the triazoles on rooting. The addition of triazoles or GA₃ to the regeneration medium reduced the formation of green meristematic nodules, which are precursors of shoots in moth bean callus. When callus was grown in the presence of either paclobutrazol or uniconazole, subsequent root and green meristematic nodule formation were reduced upon transfer to a growth regulator-free regeneration medium. The results of this study indicate that exposure of moth bean callus tissue to micromolar concentrations of triazoles or GA₃ can significantly alter in vitro growth and differentiation.     

Highly efficient transformation and regeneration of aspen plants through shoot-bud formation in root culture

The natural capacity of aspen (Populus tremula L.) roots for direct shoot-bud regeneration was harnessed to establish a highly efficient transformation and regeneration procedure that does not require a pre-selection stage on antibiotics. Aspen stem segments were transformed using wildtype Agrobacterium rhizogenes (LBA9402) with the binary p35SGUSINT plasmid carrying the genes coding for -glucuronidase (GUS) and neomycin phosphotransferase II. High levels of transient GUS expression were found in the basal cut surface of 87% of the segments, and 98% of these formed well-developed adventitious roots. Proliferating root cultures were established in liquid culture, and GUS expression was found in 75% of the roots. Shoot-bud regeneration in root cultures was very high: 99% of the roots yielded shoot-buds (4.3 buds per root), of which 91% expressed GUS. Southern blot analysis and polymerase chain reaction confirmed the transgenic nature of the plants expressing GUS. Kanamycin resistance of transformants was tested with respect to callus growth and bud regeneration. Callus from transgenic plants exhibited a high growth rate in the presence of up to 100 g/l kanamycin, and bud regeneration from transformed roots occurred in the presence of up to 30 g/l kanamycin. Callus and buds from control (non-transformed) plants failed to proliferate or regenerate, respectively, in the presence of kanamycin at concentrations above 10 g/l. Ninety-four independent clones from different transformation events were established, of which 52 were phenotypically true-to-type.Abbreviations NAA -naphthaleneacetic acid - BA 6-benzylaminopurine - GUS -glucuronidase - NPTII neomycin phosphotransferase II - PCR polymerase chain reaction - EtOH ethanol - CTAB cetyltrimethylammonium bromide - SDS sodium dodecyl sulfate - NOS nopaline synthase - CaMV cauliflower mosaic virus     

Bud burst in Norway spruce (Picea abies): preliminary evidence for age-specific rest patterns

This study examines the effect of chilling and photoperiod on rest completion and bud burst in Norway spruce [Picea abies (L.) Karst.] using twigs from both 15-year-old (young trees) and 56-year-old (old trees) trees. The material was transferred between September and May from outdoors to experimental forcing conditions with four different photoperiods. The bud burst percentage of the twigs from young trees generally increased in all photoperiods until the end of the year. After that it decreased until vernal equinox (March 20) and then increased steeply towards spring. This new observation of transient rest completion during autumn suggests that young trees have (I) a transient time window during late autumn when ontogenetic development is possible, and (ii) a secondary rest culminating approximately at the time of vernal equinox. In twigs from old trees the transient rest completion was much weaker as the bud burst percentages generally remained under 20 during autumn and winter. At vernal equinox there were no burst buds in twigs from the old trees in any photoperiod and after that the bud burst percentage increased basically in the same manner as in the young trees. The bud burst percentage of the twigs from young trees was generally higher as the photoperiod increased. However, no evidence for absolute long photoperiod requirement of rest completion was observed.     

Determination of internal dynamics of deoxyriboses in the DNA hexamer d(CGTACG)2 by 1H NMR

The conformations and internal dynamics of the deoxyriboses of d(CGTACG)₂ have been determined by NMR measurements at 15°C. The conformations of the sugars were determined using coupling constants and time-dependent NOE measurements. The J-splitting patterns of the H1, H2 and H2 resonances show that the sugars exist as mixtures of conformations near C2 endo (south) and C3 endo (north). The population of the south conformation was larger for the purines than for the pyrimidines. The overall tumbling time of the molecule in ²H₂O was determined from measurements of the cross relaxation rate constant for the H6-H5 vectors of the two cytosine residues. Order parameters were determined for the H1-H2, H2-H2 and H2-H3 vectors from measurements of cross relaxation rate constants, making use of multi-spin analysis of the NOE build up rates. These order parameters are weakly dependent of the base sequence, and except for the terminal Cyt 1 residue, the H2-H2 and H2-H3 vectors are near unity, indicating the absence of rapid pseudorotation on the nanosecond time scale. However, the order parameter for the H1-H2 vector is significantly smaller than expected for rapid pseudorotation indicating the presence of other motions of the sugars. This motion must be about an effective axis parallel to the H2-H vector, and to occur with an angular fluctuation of about 30°.The results show that to obtain highly refined structures for nucleic acids by NMR the effects of spin diffusion and motional averaging cannot be ignored.Some of this work was presented as a poster at the 30^th Experimental NMR Conference at Asilomar, California 1989     

The influence of cytokinin pulse treatments on adventitious bud formation on vegetative buds of Picea abies

Resting vegetative buds of Picea abies collected from phytotron-grown rooted cuttings of 24-year-old trees or a 12-year-old hedge were tested for their capacity to form adventitious buds after various cytokinin treatments. The most effective method for obtaining a high yield of adventitious buds within 8 weeks was to pulse treat the buds in 250 M BA for 3 h and then culture them on medium containing 5 M each of BA and kinetin for 1 week. The developmental pattern for adventitious bud production, with the formation of 10 to 20 adventitious buds per bud, was similar for all tested genotypes, although the number of buds giving rise to adventitious buds varied significantly. The capability of some clones to form adventitious buds was correlated to endogenous cytokinin content. The clone which contained most endogenous cytokinin in its resting bud had the highest potential for adventitious bud formation.     

Intraorbital cerebrospinal fluid outflow and the posterior uveal compartment of the hamster eye

Summary An ultrastructural and tracer study was undertaken to determine normal outflow pathways of cerebrospinal fluid (CSF) at the terminal subarachnoid space (SAS) of the optic nerve. In the morphological studies, the optic nerve dura and arachnoid were found to be continuous with the sclera of the eye beyond the optic nerve SAS. The pia mater is continuous with the inner sciera and the lamina fusca of the eye. Montages and serial sections demonstrated that the distal SAS is divided into numerous tortuous channels to form an arachnoidal trabecular meshwork. Spaces of this meshwork continue into microcanals which bypass the outer arachnoid barrier layers of the optic nerve meninges to reach the sclera and posterior intraorbital connective tissue. Ferritin infused into the cisterna magna entered the optic nerve SAS within 1 min and reached arachnoidal trabecular meshwork channels and the microcanals within 8 min. It then passed into intraorbital connective tissue spaces at the posterior pole of the eye. Ferritin appeared to be blocked by the lamina fusca and a newly discovered posterior compact zone which together prevented its entrance into the choroidal interstitium. These observations suggest that a subarachnoidal-scleral-orbital outflow pathway provides a route for CSF drainage from the optic nerve SAS to intraorbital connective tissue. The previously described posterior uveal compartment in the hamster eye (Kelly et al. 1983) appears to be relatively isolated from this subarachnoidal-scleral-orbital CSF outflow.Parts of this work have been presented at the 1984 meetings of the American Association of Anatomists (Shen 1984).     

Bud proliferation and plant regeneration in liquid-cultured philodendron treated with ancymidol and paclobutrazol

Philodendron plants propagated in liquid shake or bioreactor cultures proliferated profusely in the presence of paclobutrazol (PAC) and to a lesser extent in the presence of ancymidol (ANC). The growth retardants inhibited leaf development and induced the formation of bud clusters. Short transient treatments with low concentrations (1.7–3.4 M) of the growth retardants limited leaf growth and proliferation to a lesser extent than higher concentrations (6.8–17 M). The growth retardants had a carryover dwarfing effect in the semi-solid hardening medium, which was more pronounced at the higher concentrations or prolonged exposure periods. Regenerated plants resumed normal growth 3–6 weeks after transplanting. Treatment with growth retardants may become a useful method in the prevention of abnormal leaf growth in large-scale liquid cultures, as well as in enhancing bud proliferation.     

Triazole treatment of explant source provides stress tolerance in progeny of Geranium (Pelargonium hortorum Bailey) plants regenerated by somatic embryogenesis

Thehypothesis that chemically induced stress tolerance in plants can betransferredto a larger clonal population regenerated by somatic embryogenesis wasevaluatedusing the triazole compound paclobutrazol as a chemical inducer of stresstolerance in Geranium (Pelargonium horturum Bailey). Seedswere imbibed in 3.4, 10.2 or 17.0 M (1, 3, 5 mgL^–1) paclobutrazol for 24 h and germinatedfor 7 days. Hypocotyl explants were cultured in vitro toinduce somatic embryogenesis. Plants regenerated from somatic embryos wereexposed to heat stress at 56°C. Explants treated with3.4 M paclobutrazol yielded a substantially higher number ofsomatic embryos compared with untreated explants. In contrast, 17.0M paclobutrazol treatment inhibited embryogenesis producing asignificantly lower number of somatic embryos. There was no difference in theembryo number between control and 10.2 M treatment. Somaticembryos derived from 3.4 and 10.2 M paclobutrazol treatedexplants developed into plants at a faster rate than the control and 17.0M treatments. Plants derived from paclobutrazol-treatedexplants displayed a greater tolerance to heat stress compared with thecontrols. Observations in this study provide a technique for regeneratingplantsin tissue/cell culture with additional desirable traits such as stresstolerancewith minimal chemical contamination of the environment.     

The distribution of short chain carboxylic acids in eutrophic drainage channels

The concentration of the C₂–C₅ carboxylic acids in the water column and sediment of shallow, eutrophic, drainage channels (Lewes Brooks, UK) were measured by gas chromatography. The concentrations of these acids were negatively correlated with dissolved oxygen. The highest concentrations of acetate (up to 200 M), propanoate (up to 38 M) and butanoate (up to 1.2 M) were measured during the summer in the water above the sediment, which became hypoxic during this period. Both acetate and propanoate concentrations declined at night. High concentrations of the acids were also recorded in reedbeds, which were also hypoxic. Only acetate was detected in the sediment pore water (up to 168 M). Its concentration declined during the autumn and winter and with increasing depth within the sediment.Author for Correspondence     

Rationality,Representation, and the Risk Mediating Characteristics of a Karakoram Mountain Farming System

Despite emerging appreciations of contextual knowledge systems, elements of diversity in mountain farming systems are often characterized as irrational and as obstacles to achieving the production goals of 'modernized' agriculture. In this paper, I suggest that these negative representations are produced at least in part as a function of the normalization of a large-scale agriculture as rational. A case-study of a mountain farming system in the Karakoram mountains of northern Pakistan is presented to expose a contextual rationality in relation to risk minimization and to challenge characterizations of this system as 'backward,' unsophisticated and irrational. Specifically I examine the risk mediating characteristics of practices such as field dispersal, delayed planting, intercropping, and polyvarietal planting and conclude that the characteristic feature of this local farming system is a contextually rational diversity. This conflicts with the modernist paradigm of rationality and economic growth subscribed to by a local development agency. Intervention based on ill-informed interpretations of traditional practice have the potential to increase vulnerability of villagers by failing to appreciate the contextual rationality of diversity.