Effects of anaerobiosis on ethylene production, respiration and flowering in iris bulbs

Ethylene production of iris bulbs (Iris hollandica cv. Ideal) was very low. When stored at 30°C, production was 12–20 pmol C₂H₄ (kg fresh weight)^?1 h^?1. Higher temperatures (35°C, 40°C) enhanced the ethylene production; a treatment with 40°C for ca 7 days caused a 3 times higher ethylene production than at 30°. During anaerobic storage (in 100% N₂) ethylene production was equal to that of control bulbs. When after a 7 day period of anaerobiosis the N₂ was replaced by air, a burstlike ethylene production was observed. Twenty-four h after the replacement, ethylene production was equal to control values again. The effects of this production of ethylene on mitochondrial respiration and flowering were investigated. When mitochondria were isolated immediately after the anaerobic treatment (before the enhanced ethylene production) alternative pathway capacity was not detectable, a situation also occurring in control bulbs. When mitochondria were isolated 24 h after the end of the anaerobiosis (after the ethylene burst) uninhibited respiration did not change significantly, but a capacity of the alternative pathway was observed. The increase in alternative pathway capacity after anaerobiosis was partly inhibited by 2,5-norbornadiene (NBD), an ethylene antagonist. Fermentation occurred during anaerobiosis: ethanol concentrations increased during the treatment and decreased when air was supplied. When bulbs were exposed to ethanol vapour the alternative pathway was induced but only when very high ethanol levels in the bulbs were reached. The amount of ethanol accumulated in the bulbs during a 7 day anaerobic treatment was far too low to explain the observed induction of alternative pathway capacity. Flowering percentages were enhanced after a 24 h treatment with ethylene and after a 7 day anaerobic treatment. NBD significantly inhibited the effect of exogenous ethylene and of anaerobiosis on flowering. Ethanol was not able to induce flowering. The burst-like production of ethylene after anaerobiosis probably is responsible for the effects on respiration and flowering.     

Effects of nutrient availability and neighbours on shoot growth,resprouting and flowering of Erica multiflora

Abstract. To test if low soil fertility and competition limit the performance of Mediterranean shrubs, and if the effects of competition on plant performance were modified by soil fertility, we subjected shrubs of Erica multiflora to a factorial field experiment of fertilization and removal of neighbours around target plants. After 18 months of treatment, fertilization had stimulated the growth of pre-existent sprouts and biomass allocation to stems into new sprouts, but decreased the frequency of sprout flowering. Removal of neighbours increased the number and biomass of new sprouts, the probability of sprout flowering and the biomass of flowers. Fertilization slightly enhanced sprout recruitment and the probability of sprout flowering when neighbours were removed, but did not modify the other parameters of plant performance. According to our results, both low soil fertility and competition limited plant performance. Competition was slightly more intense in fertilized plants, but only in determining sprout and flowering bud stimulation.     

Vitrification of carnation in vitro: Changes in ethylene production,ACC level and capacity to convert ACC to ethylene

Carnation tissue was allowed to vitrify in liquid culture and ethylene production, ACC content and capacity to convert ACC to ethylene were measured in comparison to tissue developing normally on solid medium. Flask atmospheres of liquid cultures accumulated ethylene at a higher rate during the first four days. Daily ethylene production by vitrifying material decreased later. Ethylene emission by vitrifying tissues always remained above controls when subcultured daily to fresh medium. Explants and microsomal preparations from vitrifying carnations converted ACC to ethylene at a higher degree from the first day in liquid medium. ACC level markedly increased in vitrifying tissues during the first two days of liquid culture. Raising the level of ethylene in the atmosphere of solid cultures did not induce vitrification symptoms nor did use of inhibitors of ethylene biosynthesis in liquid cultures prevent the process. The role of ethylene in vitrification is reappraised.     

Effects of ethylene on shoot initiation,leaf yellowing,and shoot tip necrosis in roses

This study was conducted to investigate the in vitro influence of ethylene on shoot branching and leaf yellowing in the rose cultivar Tineke by using different compounds that regulate ethylene inhibition and stimulation. Aminoethoxy vinyl glycine (AVG), silver thiosulfate (STS), and sodium nitroprusside (SNP) caused enhanced apical shoot initiation and reduced leaf yellowing, via inhibition of ethylene production, in the following order: AVG > SNP > STS. In contrast, the addition of 1-aminocyclopropane-1-carboxylic acid (ACC) or 3-indoleacetic acid (IAA) stimulated ethylene production and had greater negative effects on the studied parameters than the control; the negative effects of IAA were further confirmed in combination with AVG, STS, or SNP. The effects of ethylene on apical shoot initiation and leaf yellowing in Tineke were confirmed in another rose cultivar, Innocence. Hence, this study provides strong support for the hypothesis that ethylene-inhibiting agents have beneficial effects on apical shoot initiation and reduction of leaf yellowing in other rose cultivars.     

Effects of root anaerobiosis on ethylene production, epinasty, and growth of tomato plants

Experiments were performed to determine the source(s) of ethylene-causing epinasty in flooded tomato plants (Lycopersicon esculentum Mill.). Simultaneous measurements were made of ethylene synthesized by the roots and shoots of tomato plants exposed to either aerobic or anaerobic atmospheres in the root zone. When the root zone was made anaerobic by a flowing stream of N₂ gas, petiole epinasty and accelerated ethylene synthesis by the shoots were observed. In soil-grown plants, ethylene synthesis by the root-soil complex increased under anaerobic conditions; but when grown in inert media under the same conditions, ethylene synthesis by roots remained constant or declined during the period of rapid epinastic growth by the petioles. Other characteristic symptoms of flooding, e.g. reduced growth and chlorosis, were also observed in plants with anaerobic roots. Pretreatment of plants with AgNO₃, an inhibitor of ethylene action, completely prevented epinasty, demonstrating that ethylene is the agent responsible for waterlogging symptoms. These results indicate that deprivation of O₂ to the roots is the primary effect of soil flooding, and that this is sufficient to cause increased ethylene synthesis in the shoot. The basis of the observed root-shoot communication is unknown, but root-synthesized hormones or specific ethylene-promoting factors may be involved.     

Effect of silver nitrate on sugarcane cell suspension growth, protoplast isolation, ethylene production and shoot regeneration from cell suspension cultures

Silver nitrate (AgNO₃), an inhibitor of the physiological actionof ethylene, reduced cell growth, promoted ethylene production,increased the yield of protoplasts and reduced shoot regenerationfrom sugarcane heterogeneous cell suspension cultures. The increasein the rate of protoplast isolation from cultures treated withAgNO₃ (0 to 59 µM) correlate with an increase in endogenousethylene production by the cells. The addition to the culturemedium of chemicals that either inhibited (aminoethoxyvinylglycine,AVG) or promoted (aminocyclopropane-1-carboxylic acid, ACC)ethylene biosynthesis did not alter the number of protoplastsisolated from these cultures. However, protoplasts were isolatedwith AVG in combination with AgNO₃ even though ethylene productionwas inhibited. These results suggested that AgNO₃ may be havinganother more direct effect on protoplast release. One such sitemay be the cell wall or on cell metabolism conditioning cellsto release protoplasts after enzyme treatment. Key words: Sugarcane, cell suspension, protoplast, silver nitrate, ethylene     

Canopy structures and its effect on shoot growth and flowering in subalpine forests

Changes in foliage density distribution with altitude and its effect on shoot growth and flowering were studied in forest section planes (profiles) of subalpine forests and scrubs (Krummholz) in Nepal and Japan.Patterns of foliage in forest canopy were evaluated by an analysis of variance. Foliage densities were very high at high altitude canopies, but the change in spatial patterns along altitude differs in both areas.The spatial pattern of new shoot production was similar to that of current foliage density and was affected by the amount of foliage above the sample probably through light condition. Flowering of tall trees occurred in the surface of the upper canopy, but a shrub species flowered even under tree canopies.     

The influence of ethylene on proliferation and growth of rose shoot cultures

Ethylene accumulation in four different rose in vitro culture containers was evaluated. Multiplication rate was the highest, and axes most elongated, in the two containers where ethylene accumulation was limited. Pulse treatments of ethylene at various concentrations enhanced proliferation depending on concentration (5 ppm generally was the most favourable) and time of application, while reducing elongation of the shoots. An ethylene trap in the flask atmospheres of the cultures reduced rose shoot proliferation rate but increased elongation of the axes. Inhibitors of ethylene biosynthesis, aminoethoxyvinylglycine (AVG) and cobalt chloride (CoCl₂), increased multiplication rate by providing a higher number of axes of a suitable size for subculture. The ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) had a beneficial effect on multiplication rate, although reducing longitudinal growth of the axes.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AVG aminoethoxyvinylglycine - BA benzyladenine - GA₃ gibberellic acid - IBA indolyl-3-butyric acid     

Preparation of ethylene gas and comparison of ethylene responses induced by ethylene,ACC, and ethephon

Ethylene is a gaseous plant hormone used in many physiological studies examining its role in plant growth and development. However, ethylene gas may not be conveniently available to many laboratories for occasional use, and therefore several chemicals can be used as replacements. Here we report that the kinetics of the ethylene response induced by ethylene and two widely-used ethylene replacements are different. ACC failed to efficiently replace prolonged ethylene treatments, while the decomposition products of ethephon may cause non-specific responses and the efficiency of ethephon conversion to ethylene was relatively low. A cost-effective method to prepare ethylene gas was developed. Analyzed by gas chromatography, the chemically produced ethylene exhibited an identical chromatogram to that from the commercial source. Our synthetic ethylene gave the same dose-response curve in Arabidopsis as gaseous ethylene. Our study shows that the use of the ethylene gas is essential to experiments that are sensitive to treatment duration and dosage. When ACC and ethephon are used as replacements, caution should be taken in the experimental design. For laboratories that do not have an ethylene tank, ethylene gas can be easily prepared by a chemical approach without further purification.     

Effects of water and a nutrient pulse supply on Rosmarinus officinalis growth,nutrient content and flowering in the field

Rosmarinus officinalis is a dominant shrub species of calcareous Mediterranean communities that has increased its presence in wide areas due to fire frequency increase and field abandonment. We aimed to study the capacity of adult shrubs to respond to nutrient pulses such as those produced by fires and human driven eutrophycation. In a 5 years old post-fire Mediterranean shrubland we conducted an experiment to investigate the effects of irrigation and N and P fertilisation on the growth, nutrient status and flowering effort of adult plants of the dominant shrub R. officinalis in a post-fire shrubland. The responses were monitored during the immediate 3 years after fertilisation. P fertilisation increased plant growth, produced a great increase in P aerial mineralomass and P concentration in leaf and stems and had a slight positive effect on flowering effort. Irrigation increased plant growth, but did not have significant effects on nutrient contents and flowering. The results show that adult individuals of the Mediterranean shrub R. officinalis have a notable capacity to positively respond in growth and in nutritional status to a sudden increase of the limiting nutrient, in this case P, and in a lesser extent, to an increase of water supply. These capacities may be important under the more unpredictable nutrient and water availability conditions expected for the near future; they will allow to take advantage of the pulses of higher nutrient and water availability in the middle of dry periods, thus increasing the community capacity to improve the nutrient retention in the ecosystem.     

Gibberellins and bud break,vegetative shoot growth and flowering in Metrosideros collina cv. Tahiti

Applications of the growth promotive gibberellins (GAs) GA₄ and 2,2-dimethyl GA₄, and of C-16,17 endo-dihydro GA₅, which is known to promote flowering while inhibiting stem growth in the long-day grass Lolium temulentum, were made to micropropagated plants of Metrosideros collina cv. Tahiti, a highly ornamental cultivar with an intermittent flowering pattern. Gibberellin A₄ and 2,2-dimethyl GA₄ stimulated vegetative growth both in elongating shoots, and internodes of shoots developing from buds that were quiescent at the time of GA application. Abscission of the apices of expanding shoots, a feature of mature Metrosideros plants, was inhibited by these GAs, the rejuvenation of micropropagated plantlets being enhanced. However, C-16,17 endo-dihydro GA₅ differed from GA₄ and 2,2-dimethyl GA₄ by having no promotive effects on vegetative growth, and no inhibition of apical abscission. Notwithstanding this contrasting effect on vegetative growth, high doses of GA₄ or C-16,17 endo-dihydro GA₅ similarly reduced flowering on shoots to which either GA was applied. Reduced flowering in response to applied GAs is common in many woody angiosperms, and in this instance was probably the combined result of abortion of developing floral structures in quiescent buds, and a preferential inhibition of bud break for floral buds relative to vegetative buds, particularly by GA₄. Finally, both C-16,17 endo-dihydro GA₅ and GA₄ strongly inhibited bud break in this woody angiosperm, although GA₄ could initially stimulate bud break when applied to vegetative buds close to the expansion stage. The above findings, in toto, highlight the sensitivity of Metrosideros to both classes of GA in a variety of growth and development processes.     

ABA, ethylene and the control of shoot and root growth under water stress.

The question of whether abscisic acid (ABA) acts as an inhibitor or promoter of shoot growth in plants growing in drying soil is examined, drawing on current understanding of the role of ABA in root growth maintenance. Particular consideration is given to studies of endogenous ABA deficiency, which have shown that an important role of ABA is to limit ethylene production, and that this interaction is involved in the effects of ABA status on shoot and root growth.     

Light intensity, gibberellin content and the resolution of shoot growth in Brassica

The role of gibberellins (GAs) in the regulation of shoot elongation is well established but the phytohormonal control of dry-matter production is poorly understood. In the present study, shoot elongation and dry-matter production were resolved by growing Brassica napus L. seedlings under five light intensities (photon flux densities) ranging from 25 to 500 μmol m⁻² s⁻¹. Under low light, plants were tall but produced little dry weight; as light intensity was increased, plants were progressively shorter but had increasing dry weights. Endogenous GAs in stems of 16- and 17-d-old plants were analyzed by gas chromatography-selected ion monitoring with [²H₂] internal standards. The contents of GAs increased dramatically with decreasing light intensity: GA₁, GA₃, GA₈ and GA₂₀ were 62, 15, 16 and 32 times higher, respectively, under the lowest versus highest light intensities. Gibberellin A₁₉ was not measured at 25 μmol m⁻² s⁻¹ but was 9␣times greater in the 75 compared to 500 μmol m⁻² s⁻¹ treatment. Shoot and hypocotyl lengths were closely positively correlated with (log) GA concentration (for example: r ² = 0.93 for GA₁ and hypocotyl length) but shoot dry matter was negatively correlated with GA concentration. The application of gibberellic acid (GA₃) produced elongation of plants grown under high light, indication that their low level of endogenous GA was limiting shoot elongation. Although endogenous GA₂₀ showed the greatest influence of light treatment, metabolism of [³H]GA₂₀ and of [³H]GA₁ was only slightly influenced by light intensity, suggesting that neither 2β- nor 3β-hydroxylation were points of metabolic regulation. The results of this study indicate that GAs control shoot elongation but are not directly involved in the regulation of shoot dry weight in Brassica. The study also suggests a role of GAs in photomorphogenesis, serving as an intermediate between light condition and shoot elongation response. Received: 18 June 1998 / Accepted: 29 July 1998     

Effects of irradiance on growth and flowering in the shade plant, cineraria

Effects of total irradiance on growth and flowering were studied in cineraria cv. Cindy Blue grown under warm (mean 21°C) glasshouse conditions. Efficiency of light conversion for leaf and shoot dry weight increase were reduced from 0.08 to 0.02 as the mean daily light integral increased from 0.9 to 4.4 MJ m^-2 day^-1 but no significant difference in leaf area were associated with this. Specific leaf area decreased exponentially from 0.07 to 0.02 m²g¹ over the cumulative irradiance range 23 to 127 MJ m^-2 after the start of treatments and thereafter remained stable. A light integral of 19.2 MJ m^-2 were required for initiation of one leaf in plants grown under a daily integral of 4.4 MJ m^-2 day^-1, as compared with only 5.1 MJ m^-2day^-1 required per leaf in plants grown at less than 0.9 MJ m^-2day^-1. Neither chronological duration of juvenile development nor leaf number below the flower was affected by irradiance. However, as the rate of leaf initiation increased with irradiance up to 2.4 MJ m^-2day^-1 so the rate of progress to flower visibility increased linearly with irradiance over the same range. This rate then remained constant from 2.4 to 4.4 MJ m^-2day^-1. Length of the main flowering shoot decreased and the number of flowering shoots increased as irradiance increased from 0.9 to 2.4 MJ m^-2 day^-1 and then remained unchanged by further increases in irradiance.     

Effect of gibberellic acid on ACC content,EFE activity and ethylene release by floral parts of the senescing carnation flower

The application of gibberellic acid via the stem of intact preclimacteric carnation flowers inhibited the climacteric surge of ethylene evolution by the flowers. Gibberellic acid also inhibited the rate of ethylene production by all individual floral parts during both the early preclimacteric (low basal level of ethylene production) and the later climacteric stages of flower development. The extent of inhibition did however, vary from one floral part to another. The most pronounced inhibition was recorded in the petal bases between the preclimacteric and senescing stages. This suggests that the petal base is an important regulatory site for ethylene production and therefore may be involved in controlling the onset and degree of petal inrolling. In all floral parts endogenous levels of ACC were reduced with GA₃ treatment, being more pronounced in the petal bases. The potential of the flowers to convert applied ACC to ethylene was not deminished by gibberellic acid.Abbreviations GA₃ gibberellic acid - ACC 1-aminocyclopropane-1-carboxylic acid - EFE ethylene forming enzyme     

Effects of shoot bending of apple trees on accumulation and translocation of14C-labelled assimilates

The translocation of¹⁴C-labelled assimilates from a single leaf in bent and intact apple shoots was studied in varying stages of shoot development. In actively growing shoots¹⁴C-labelled assimilates translocated from the treated leaf and accumulated mainly in the shoot apex. In moderately growing apple shoots radioactive assimilates were translocated from the treated leaf in both directions towards and down the shoot. In apple shoots showing only slight growth activity the¹⁴C-labelled assimilates were transported from the treated leaf mainly to the base of the shoot, stem and roots. Bending shoots changed the pattern of distribution of radioactive assimilates. Bending actively and moderately growing shoots resulted in higher concentration of 14-carbon in the shoot apex than in controls. In slowly growing and non-growing apple shoots bending caused a higher accumulation of radioactive assimilates in the bent section than in an equal section of control shoots.     

Effects of exogenous ethylene on ethylene production in citrus leaf tissue

Exogenous ethylene stimulated ethylene production in intact citrus (Citrus sinensis L. Osbeck cv. “Washington Navel”) leaves and leaf discs following a 24-hour exposure. Studies with leaf discs showed that ethylene production decreased when ethylene was removed by aeration. The extent of stimulation was dependent upon the concentration of exogenous ethylene (1-10 microliters per liter). Silver ion blocked the autocatalytic effect of ethylene at concentrations of 0.5 millimolar and lower, but increased ethylene production at higher concentrations. The stimulating effect of ethylene resulted from the enhancement of both 1-aminocyclopropane-1-carboxylic acid (ACC) formation and the conversion of ACC to ethylene. Whereas autocatalysis was evident following 24 hours incubation, autoinhibition of wound- and mannitol-induced ethylene production was observed during the first 24-hour incubation. Ethylene treatment during this period resulted in a marked decrease in ACC levels and ethylene production rates. Furthermore, in leaf discs treated for 24 hours with ethylene, ethylene production rates increased greatly during the first 2 hours after removal of exogenous ethylene by aeration. This increase was eliminated if the discs were transferred to propylene instead of air, indicating that the autocatalytic effect of ethylene is counteracted by its autoinhibitory effect. It is suggested that autocatalysis involves increased synthesis of ACC synthase and the enzyme responsible for the conversion of ACC to ethylene, whereas autoinhibition involves suppression of the activity of these two enzymes.