Growth of rose flower peduncles and effects of applied plant growth regulators

Removal of flower buds results in abscission of peduncles of the rose cv. Nubia and cessation of peduncle growth in cv. Mercedes. Peduncle growth was inhibited when pistils and stamens were removed, but was not affected by removal only of sepals and petals. Growth of the decapitated peduncles of Mercedes was partially restored by the application of auxin in lanolin paste on the base of the peduncle and was completely restored by the application of gibberellin, while the combined application of auxin and gibberellin was the most effective for growth restoration. Growth of non-decapitated Nubia peduncles was promoted by application of gibberellin or gibberellin and auxin but not auxin alone.Peduncle elongation of both cultivars was not affected by application of cytokinin and the effect of gibberellin was antagonized by combined application with cytokinin. The peduncles strength (resistance to bending) was affected more strongly by auxin than by gibberellin, and most strongly when auxin and gibberellin were combined. The effect of auxin on the strength of peduncles, but not of gibberellin, was antagonized by application of cytokinin. Excised, non-decapitated flowering stems of Nubia treated with gibberellin and auxin in situ, showed, recovery of the peduncles from wilting after exposure to heat conditions.     

Control of mushroom sciarid fly Lycoriella ingenua populations with insect growth regulators applied by soil drench

Mushroom sciarid fly Lycoriella ingenua (Dufour, 1839) comb. nov., is one of the most common fly pests affecting the cultivation of Agaricus bisporus (Lange) Imbach in Turkey. In this study, eight insect growth regulators (IGRs)--diflubenzuron, flufenoxuron, lufenuron, methoprene, novaluron, pyriproxyfen, teflubenzuron, and triflumuron-were tested for their potential to control L. ingenua populations in two successive growing periods. Treatments were targeted at larvae as soil drenches; treatment efficacy was evaluated by assessing adult emergence and larval damage. These products were compared with a control treated with water (negative control) and a conventional chemical insecticide (chlorpyrifos ethyl) (positive control). Treatments with the IGRs caused significant reductions in emerging adult numbers and sporophore damage rates compared with the water-treated control over the two growing periods. Of the IGRs tested, novaluron, diflubenzuron, and teflubenzuron had significantly lower numbers of emerging adults than the rest of the IGRs and chlorpyrifos ethyl-treated control in both periods. Treatments with teflubenzuron, pyriproxyfen, novaluron, and diflubenzuron resulted in significantly lower sporophore damage rates than all other treatments. Compared with negative control, there were no significant yield reductions due to applications of selected IGRs. The results suggest that all the IGRs tested can be used as alternatives to conventional pesticides in controlling L. ingenua populations on mushroom.     

Effect of growth regulators on proton transport through cytoplasmic membrane of potato tuber cells

Effects of the growth regulators epibrassinolide-694 (EB), gibberellic acid (GA), and abscisic acid (ABA) on the ATP-dependent translocation of H+ through the membranes of plasma membrane vesicles of potato (Solanum tuberosum L.) tuber cells were studied. The ATP-dependent accumulation of H+ in the plasma membrane vesicles from dormant tubers was inhibited by EB and ABA and stimulated by GA. After the break of dormancy, the stimulatory effect of GA increased, the inhibitory effect of ABA decreased, and EB stimulated the accumulation of H+ in the vesicles. The data suggest that the plasma membrane H+ ATPase is a target of phytohormones that regulate the dormancy of potato tubers.     

Retardation of tree growth by injection of plant growth regulators

Previously topped American sycamore (Platanus occidentalis L.), cottonwood (Populus deltoides Bartr. ex Marsh), water oak (Quercus nigra L.), and bigleaf maple (Acer macrophyllum Pursh) trees were injected with aqueous solutions of maleic hydrazide or dikegulac-sodium in April-June, 1979 at various locations around the United States. Measurements made later in the autumn showed that dikegulac-sodium reduced sprout regrowth in all four species, whereas maleic hydrazide was only effective in controlling regrowth of American sycamore and cottonwood. The effects of dikegulac persisted through the second growing season. Significant variability was observed among treated trees and must be reduced in order to achieve consistent growth responses from an application of growth retardants.This paper reports the results of research only. Mention of a growth regulator does not consitute a recommendation for use by the U.S. Department of Agriculture nor does it imply registration under FIFRA as amended. Mention of a trademark or propriety product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable.     

Endogenous plant growth regulators and rooting capacity of different walnut tissues

Rooting ability of three different materials, namely cotyledonar linking areas, cotyledonary portions and embryonic microshoots from walnut seeds was determined. It was shown that while cotyledonar linking areas may be defined as a espontaneous rooting system, the other two tissue types correspond to inducible rooting systems, needing exogenous application of auxins for root induction. Endogenous zeatin and isopentenyl type cytokinins, indole-3-acetic acid (IAA), and abscisic acid (ABA) contents were determined in the three kinds of plant material prior to their culture. Our results show that the most active rooting systems has high levels of cytokinins, particularly dihydrozeatin (diH)Z and its riboside, and low levels of IAA and ABA. This situation could indicate that oxidative metabolism was taking place in cotyledonar linking areas, which is generally associated with the initiation phase of the rooting process. So that, we can assume that the induction phase is already overpassed in these tissues. On the contrary, the other two systems in which high levels of auxins and reduced levels of cytokinins were found, need to undergo the induction phase to be able to show root manifestation. In this case, the exogenous auxins are responsible for triggering this process, by enhancement of oxidative conditions. Therefore, it can be conclude that dynamics of growth regulators levels during the different phases of rooting are more important than specific single levels at fixed time.     

Thermoregulation during mild exercise at different circadian times

Eight healthy subjects exercised at 90 watts on a cycle ergometer on four occasions, at times close to the minimum, maximum rate of rise, maximum, and maximum rate of fall of their resting core temperature. The duration of exercise was determined by the time taken for the core (rectal) temperature to reach an equilibrium value. Forearm skin blood flow and temperature were measured regularly during the exercise, as were heart rate and ratings of perceived exertion. Sweat loss was calculated by weighing the subjects nude before and after the exercise. The rise of heart rate was not significantly different at the four times of exercise, though the rating of perceived exertion was greatest at 05:00 h. Resting core temperatures showed a significant circadian rhythm at rest (the timing of which confirmed that exercise was being performed at the required times), but the amplitude of this rhythm was decreased significantly by the exercise. The initial rate of rise of core temperature, and the total rise from the resting to the equilibrium value, were both inversely proportional to resting temperature. The time-course of the rise was accurately described by a negative-exponential model, but this model gave no evidence that the kinetics of the equilibration process depended upon the time of day. The thermoregulatory responses to the rise in core temperature—the amount of total sweat loss and rises in forearm skin blood flow and temperature—differed according to the time of exercise. In general, the responses were significantly greater at 17:00 h compared with 05:00 h, and at 23:00 h compared with 11:00 h. The results accord with predictions made on the basis of previous work by us in which core temperature rhythms have been separated into components due to the endogenous body clock and due to the direct effects of spontaneous activity. The results are discussed in terms of the ecological implications of the differing capabilities of humans to deal with heat loads produced by spontaneous activity or mild exercise at different phases of the circadian rhythm of resting core temperature.     

Effect of plant growth regulators on evolution of ethylene and methane by different explants of chickpea

Shoot tips, cotyledonary nodes and hypocotyls of chickpea (Cicer arietinum L.) were grown on 3 media: plant induction medium (PIM), callus induction medium (CIM), and shoot induction medium (SIM). Maximum growth and differentiation was seen in PIM, whereas minimum was observed in CIM. Shoot tips which differentiated to multiple shoots evolved negligible amounts of ethylene. Maximum ethylene evolution was recorded by hypocotyls in PIM. Ethylene appears to have stimulatory effect on shoot bud differentiation in cotyledonary nodes. But in hypocotyls, increased ethylene inhibited growth and differentiation. Calli on media containing only auxin (PIM) evolved significantly more ethylene, whereas those on media with cytokinin (SIM) evolved more methane. Callus forming explants like cotyledonary nodes and hypocotyls evolve more ethylene than shoot tips. This revised version was published online in August 2006 with corrections to the Cover Date.     

Dynamics of uptake, distribution and utilization of nitrogen applied at different times after planting in a Eucalyptus grandis plantation

N fertilizer labelled with ¹⁵N was used to follow the accumulation and distribution of N applied at different times after planting Eucalyptus grandis W Hill ex Maiden seedlings in south-eastern Queensland, Australia. The first application was made to selected trees at 0.12 y after planting (T₀), and treated trees were harvested at intervals after. Further labelled applications were made on different sets of trees 0.50, 0.74, 1.30 and 1.49 years after T₀; T_0.5, T_0.74, T_1.30 and T_1.49 respectively. After 0.5 y there was no significant difference in growth between T₀ trees and unfertilized controls, but after 1 y above-ground biomass and N content of the controls was only 30% and 39% of the fertilized trees respectively (P <0.05). At later applications controls were not significantly different from fertilized trees up to 1 y later, but after 2 y above-ground biomass and N content was reduced (P <0.05). Growth reductions occurred after leaves present on the tree at the time of fertilizer application were shed. Leaf biomass and N content increased steadily to age 1.5 y and then stabilized at about 2.5 kg tree^-1 and 35 g tree^?1 respectively, new growth balanced by litter fall. N content in woody material (stems+branches) increased steadily, equaling that of the leaves at 3.5 y. N derived from fertilizer and the proportion of applied N recovered peaked at 1 y and then decreased. These relationships were not affected by time of application. In T₀ trees N in above-ground parts derived from fertilizer increased steadily to 42% of the total 0.5 y after application. It then decreased rapidly after leaf fall commenced while total N content increased. When observations ceased 3.5 y after planting, less than 5% of the N in the trees was derived from fertilizer. N uptake was two-phased. In the first year mineral N from the fertilizer was taken up by the trees. In subsequent years fertilizer contributed to the tree growth but the N taken up came from a different source.     

Modulation of human granulopoiesis by macrophage-derived growth regulators

The response of granulocyte progenitors (CFU-D) from patients with chronic myeloid leukaemia (CML), neutrophilic reaction (NR) and healthy subjects to macrophage-derived stimulatory and inhibitory factors was investigated in diffusion chamber culture. CFU-D from CML and NR demonstrated a normal reactivity to macrophage stimulation but were hyporesponsive to indomethacin-sensitive inhibition. It is also shown that the spleens of patients with Hodgkin's disease contain locally activated macrophages with higher production of indomethacin-sensitive growth inhibiting factor for autologous CFU-D clonal proliferation.     

The effect of plant growth regulators on formation of crown gall tumors on potato tuber discs

The effect of several plant growth regulators on the number of tumors developing on potato tuber discs (Solatium tuberosum L. cv. Radka) inoculated withAgrobacterium tumefaciens, strain C 58 was studied. The plant growth regulators used in appropriate range of concentrations stimulated the formation of tumors byA. tumefaciens. Naphthaleneacetic acid (NAA) was most active in concentration of 10⁻⁴ mg ml⁻¹. Kinetin gave a biphasic response with optimal promotions of tumor initiation at 10⁻⁴ − 2 × 10⁻³ mg ml⁻¹. High kinetin concentration (10⁻¹ mg ml⁻¹) inhibited the formation of tumors completely. Indoleacetic acid (IAA) stimulated the initiation of tumors in the same range of concentrations as kinetin, except that very high concentrations did not inhibit but enhanced tumor formation. 2,4-diehlorphenoxyacetic acid (2,4-D) showed a biphasic response with maxima in 10⁻⁴ mg ml⁻¹ and 10⁻¹ mg ml⁻¹. All the tumors scored for nopaline production showed nopaline synthase activity independently whether their formation was stimulated by l0⁻¹ mg ml⁻¹ IAA or they were initiated without any treatment by plant growth regulators.     

Phase shifting by novelty-induced running: activity dose-response curves at different circadian times

This study compared phase shifting after novelty-induced running at different circadian times (CTs). In Experiment 1, hamsters were confined to novel wheels for 3 h, starting at CTs 2, 4, 6, 8, 10 or 22. The largest shifts were found at CTs 2, 4 and 6. At each CT there was a relationship between the number of revolutions during the pulse and the size of phase shift. Maximum shifts were usually observed at each CT when animals ran 5000–9000 revolutions during the pulse. In Experiment 2, hamsters were confined to novel wheels for 1 h, also starting at CTs 2, 4, 6, 8, 10 or 22. Unlike with 3-h pulses, the largest shifts with 1-h pulses occurred at CT 8. In Experiment 3, hamsters were shut into a small nest box after a 1-h pulse at CT 8; phase shifting was unaffected, showing that movement about the home cage after a 1-h pulse had ended was not required for shifting. At CTs 2, 4 and 22, 3-h pulses produced shifts but 1-h pulses did not. Possibly, there are two different mechanisms of nonphotic phase shifting that can be activated by being placed in a novel wheel, but the results can also be explained in terms of a single mechanism. Accepted: 8 August 1997     

Modification of root bud growth in Canada thistle with selected plant growth regulators: effects on translocation of glyphosate

Root applications of 0.1 M 6-benzyladenine (BA) and 10.0 M indole-3-butyric acid (IBA) enhanced or inhibited, respectively, root bud growth in hydroponically grown Canada thistle [Cirsium arvense (L.) Scop.]. Translocation of¹⁴C-glyphosate [N-(phosphonomethyl)glycine] into roots was positively correlated with this growth. Foliar applications of ethephon or chlorfluorenol also enhanced root bud growth, but glyphosate translocation was only weakly correlated with such growth in soil-grown Canada thistle. At glyphosate rates above 0.56 kg/ha, root bud growth was not stimulated by plant growth regulators (PGRs) and basipetal translocation was not enhanced. Paradoxically, ethephon and chlorflurenol restrained root bud growth in the field since thistle control steadily improved during the 3 years following treatment.     

Growth regulators in changing apical growth at transition to flowering

Reorganization of growth in the shoot apex ofChenopodium rubrum during transition to flowering is described. Growth and morphogenic changes — a rise in cell division rate, changes in leaf and bud formation and changes in directions of cellular growth — are viewed from the aspect of a possible role of growth hormones in controlling these changes. Growth and morphogenic effects of exogenous growth regulators in the shoot apex ofChenopodium are summarized and their floral effects explained in terms of changing apical growth correlations. New evidence concerning the timing of increased cell division rate and showing the limited requirement of axillary cell division and a shift to more vertical direction of growth in the apex in the floral developmental pathway was obtained in experiments with kinetin application and by surgical treatments.     

Micropropagation ofAsparagus cooperi as affected by growth regulators

For clonal propagation ofAsparagus cooperi, shoot tips and node explants of 7, 20 and 35 d old spear from the region within 10 cm and below 25 cm from the apex were cultured in modified Murashige and Skoog's (1962) medium containing 6-benzylaminopurine (BAP). The required concentration of BAP varied in explants of different ages and types. In shoot tip culture, the rate of shoot multiplication was higher after 40 d than 60 d of culture. The maximum mumber (62–65) of shoots were obtained from shoot tip explants of 20 d old spear in the medium containing 2.0 mg dm⁻³ of BAP, 80 mg dm⁻³ of adenine and 0.02 mg dm⁻³ of α-naphthalene acetic acid after 60 d of culture. From node cultures, high number of shoots were obtained after 30 d. Pretreatment with BAP in liquid medium for 48 h was effective for semirejuvenescence. The individual shoots produced roots in presence of indole-3-butyric acid and also in potassium salt of indole-3-butyric acid, the later being more effective. All regeneratns were cytologically stable.     

Effects of variation in temperature and light intensity at different times on growth and yield of spring wheat

Spring wheat grown in pots outdoors was transferred to growth rooms for various periods to study the effect of increasing the temperature from 14-4 to 20-3 ^oC (Expt 1) or from day/night values of 15-0/15-2 to 20-0/15-2 ^oC (Expt 2) and of increasing the amount of visible radiation in a 16 h day from 424 to 792 J cm^-2 (Expt 1) or 374 to 740 J cm^-2 (Expt 2). There were no interactions between temperature and radiation. In Expt 1 neither the increase in temperature nor extra radiation, applied for 14 days immediately after the appearance of double ridges on the stem apex, or 14 days later, increased grain yield at maturity. Warmth early, but not late, increased dry weight, leaf area and the number of floret primordia immediately after treatment, but these effects had disappeared by anthesis, 30 days later. Dry weight but not leaf area was increased by extra radiation but the effects had disappeared 2 wk after treatment. An increase in temperature imposed for 16 days starting 5 or 21 days after anthesis (Expt 2) increased dry weight of the ear and decreased that of the rest of the plant immediately after treatment, and decreased leaf area at all times. When plants from the two temperatures were put together in the same conditions, ear growth of plants that had been in the warm was slower than that of plants from the cold treatment, so that the difference in ear weight observed after 16 days of treatment reversed and grain yield was decreased by warmth applied in either period; the component of yield decreased by warmth was grain size. Additional radiation in either post-anthesis period increased dry weight of all parts of the plant and had negligible effects on leaf area. Final grain yield was increased by c. 15% because the individual grains were larger. Early treatment also increased grain number slightly. The effects of treatment during the two post-anthesis periods were similar in size, and additive.     

Effects of chemical treatments for mildew control at different times on the growth and yield of spring barley

Experiments in 1973 and 1974 tested the effects of ethirimol seed treatment and the timing of single sprays of ethirimol or tridemorph, on mildew control and the growth and yield of spring barley. These treatments were compared with selected combinations of two treatments designed to give longer protection. In 1973, combinations of seed treatment and spray, or two sprays, did not yield better than the best component treatment applied alone or the most effective single spray of tridemorph applied on 1 June. In 1974, mildew developed usually early and yields were increased by applying ethirimol to the seed plus a tridemorph spray or two tridemorph sprays. However, barley sprayed once with tridemorph on 20 May, the expected best date, yielded more than barley receiving a seed treatment of ethirimol plus a tridemorph spray applied on either 3 or 12 June. Sprays of captafol and tridemorph, applied as separate treatments, successively to the same plots on three occasions, gave the best yields in both years. Treatments most affected ear number but they did have some effect on all components of yield. In 1974 there was a significant relationship between ear number and the variance of the number of grains per ear.     

Human plasma DSIP decreases at the initiation of sleep at different circadian times

Nocturnal plasma delta sleep-inducing peptide-like immunoreactivity (DSIP-LI) was determined serially in seven healthy male subjects. Time courses during nocturnal sleep (2300-0800 h), nocturnal sleep deprivation (2300-0500 h), and morning recovery sleep (0500–0800 h) after sleep deprivation were compared. A significant decrease in plasma DSIP-LI was found at the transition from wakefulness to sleep in both evening sleep (2300 h) and morning recovery sleep (0500 h). Time courses were accompanied by physiological changes in sleep electroencephalographic slow-wave activity, and in plasma concentrations of cortisol and human growth hormone. No sleep stage specificity was found. It is concluded that DSIP is influenced by the initiation of sleep.