Relationship between Indole-3-Acetic Acid Levels in Apple (Malus pumila Mill) Rootstocks Cultured in Vitro and Adventitious Root Formation in the Presence of Indole-3-Butyric Acid

In vitro rooting response and indole-3-acetic acid (IAA) levels were examined in two genetically related dwarfing apple (Malus pumila Mill) rootstocks. M.26 and M.9 were cultured in vitro using Linsmaier-Skoog medium supplemented with benzyladenine (BA), indole-3-butyric acid (IBA), and 1,3,5-trihydroxybenzoic acid (PG). Rooting response was tested in Lepoivre medium supplemented with IBA and PG. IBA concentrations of 12.0 and 4.0 micromolar induced the maximum rooting percentages for M.9 and M.26, respectively. At these concentrations rooting response was 100% for M.26 and 80% for M.9. Free and conjugated IAA levels were determined in M.26 and M.9 shoots prior to root inducing treatment by high performance liquid chromatography with fluorescence detection and validated by gas chromatography-mass spectrometry using ¹³[C₆]IAA as internal standard. Basal sections of M.26 shoots contained 2.8 times more free IAA than similar tissue in M.9 (477.1 ± 6.5 versus 166.6 ± 6.7 nanograms per gram fresh weight), while free IAA levels in apical sections of M.26 and M.9 shoots were comparable (298.0 ± 4.4 versus 263.7 ± 9.3 nanograms per gram fresh weight). Conjugated IAA levels were significantly higher in M.9 than in M.26 indicating that a greater proportion of total IAA was present as a conjugate in M.9. These data suggest that differences between M.26 and M.9 rooting responses may be related to differences in free IAA levels in the shoot base.     

Effect of Exogenous Indole-3-Acetic Acid and Indole-3-Butyric Acid on Internal Levels of the Respective Auxins and Their Conjugation with Aspartic Acid during Adventitious Root Formation in Pea Cuttings

The influence of exogenous indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) on the internal levels of these auxins was studied during the first 4 days of adventitious root formation in cuttings of Pisum sativum L. The quantitations were done by high performance liquid chromatography with spectrofluorometric detection. IBA, identified by combined gas chromatography-mass spectrometry (GC-MS), was found to naturally occur in this plant material. The root inducing ability of exogenous IBA was superior to that of IAA. The IAA level in the tissue increased considerably on the first day after application of IAA, but rapidly decreased again, returning to a level twice the control by day 3. The predominant metabolic route was conjugation with aspartic acid, as reflected by the increase in the level of indole-3-acetylaspartic acid. The IBA treatment resulted in increases in the levels of IBA, IAA, and indole-3-acetylaspartic acid. The IAA content rapidly returned to control levels, whereas the IBA level remained high throughout the experimental period. High amounts of indole-3-butyrylaspartic acid were found in the tissue after feeding with IBA. The identity of the conjugate was confirmed by ¹H-nuclear magnetic resonance and GC-MS. IBA was much more stable in solution than IAA. No IAA was detected after 48 hours, whereas 70% IBA was still recovered after this time. The relatively higher root inducing ability of IBA is ascribed to the fact that its level remained elevated longer than that of IAA, even though IBA was metabolized in the tissue. Adventitious root formation is discussed on the basis of these findings.     

Shikimic Acid in the Leaves of Eucalyptus sieberiana F. Muell.

Shikimic acid was determined in leaves, at different stagesof growth, from 1- and 4-year-old specimens of Eucalyptus sieberianaF. Muell. A linear relationship was found between the shikimicacid concentration (mg./g.) and the weight of the leaf up tothe point where the leaf had reached full size. As the leavesbecame older the shikimic acid content decreased.     

Effect of Sucrose Concentration, Charcoal, and Indole-3-Butyric Acid on Germination of Abies Numidica Somatic Embryos

The dependency of radicle elongation in Abies numidica somatic embryos on germination media has been studied. No significant differences were detected between the Murashige and Skoog (MS) and Schenk and Hildebrandt (SH) medium. The addition of 10 g dm^–3 activated charcoal or 0.05 mg dm^–3 indole-3-butyric acid (IBA) into both media had positive influence on embryo germination. Difference between activated charcoal and IBA effects were significant. The high rooting percentage (85 %) was recorded on half SH medium with 10 g dm^–3 sucrose and activated charcoal. After IBA addition rooting percentage was increased to 95 %. During 7 months 73 % of plantlets survived transfer to soil and in 54 % of plantlets shoot growth was observed.     

Different Behaviour of Indole-3-Acetic Acid and Indole-3-Butyric Acid in Stimulating Lateral Root Development in Rice (Oryza sativa L.)

The plant hormone auxin has been shown to be involved in lateral root development and application of auxins, indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA), increases the number of lateral roots in several plants. We found that the effects of two auxins on lateral root development in the indica rice (Oryza sativa L. cv. IR8) were totally different from each other depending on the application method. When the roots were incubated with an auxin solution, IAA inhibited lateral root development, while IBA was stimulatory. In contrast, when auxin was applied to the shoot, IAA promoted lateral root formation, while IBA did not. The transport of [³H]IAA from shoot to root occurred efficiently (% transported compared to supplied) but that of [³H]IBA did not, which is consistent with the stimulatory effect of IAA on lateral root production when applied to the shoot. The auxin action of IBA has been suggested to be due to its conversion to IAA. However, in rice IAA competitively inhibited the stimulatory effect of IBA on lateral root formation when they were applied to the incubation solution, suggesting that the stimulatory effect of IBA on lateral root development is not through its conversion to IAA.     

The effect of soil desiccation on the nutrient status of Eucalyptus regnans F. Muell seedlings

The poor growth of young Eucalyptus regnans seedlings in undried soil from the mature forest of E. regnans can be overcome by previously air-drying the soil or by adding sufficient amounts of complete soluble fertilizer or equivalent concentrations of P (as NaH₂PO₄) and N (as NaNO₃). A factorial pot experiment in which phosphate and nitrate were added to undried soil indicated that P was the primary deficiency for young seedlings and that response to N did not occur until this lack was satisfied. In dried soil, seedlings also responded to additions of complete fertilizer but most of this effect was due to N rather than P. Field trials in the mature forest also indicated greater growth in dried soil than undried soil and confirmed a response of young seedlings to superphosphate. In pot experiments, the concentration of P and N per g plant dry weight after four months was relatively constant irrespective of the final size of the plant. Seedlings in dried soil extracted up to 15 times more P than did those grown in undried soil. In general, chemical analysis of soil indicated more extractable P and N from dried soil although this was not always consistently so. Soil desiccation resulted in an increase in soil surface area due to the fragmentation of larger peds and to an increase in the number of microfractures which remained in the soil crumbs after rewetting. Mycorrhiza are likely to be important since the differentiation of the growth response of seedlings in dried and undried soil, which occurred at 5–6 weeks, corresponded with the establishment of full ectomycorrhizal development (80% root tips). The factors concerned with the increase in fertility after air-drying are discussed.Abbreviations GR Growth Ratio     

Effect of Deseeding on the Indole-3-acetic Acid Content of Shoots and Roots of Zea mays Seedlings

We wished to determine the effect of endosperm removal on the amounts of free and esterified indole-3-acetic acid (IAA) in young Zea mays seedlings. The increases of IAA derived from endosperm and from biosynthesis, but without correction for catabolic losses, were 0.9 picomole of free IAA per shoot per hour, and 1.1 picomoles per shoot per hour of ester IAA. After deseeding, free IAA in the shoot declines by 40% following kernel removal and total (free + ester) IAA declines at a rate of about 1 picomole per shoot per hour. A slight, but insignificant increase of ester IAA occurs following endosperm removal. In the primary roots, the decreases of free IAA and total (free + ester) IAA are accelerated by seed removal. Thus, the endosperm appears to be a major source of IAA for the shoot and root.     

Characterization and Rooting Ability of Indole-3-Butyric Acid Conjugates Formed during Rooting of Mung Bean Cuttings

Indole-3-butyric acid (IBA) is rapidly metabolized by mung bean cuttings during rooting. Twenty-four hours after application, less than 20% of the applied IBA remained in the free form and its level decreased continuously in the later stages of rooting. Indole-3-butyrylaspartic acid (IBAsp) and at least two high molecular weight conjugates were the major metabolites in IBA-treated cuttings. In the latter conjugates, at least part of the IBA moiety is attached to a high molecular weight constituent in an amide linkage. IBAsp level peaked 24 hours after application of IBA to the cuttings and then declined. The level of the high molecular weight conjugates increased continuously throughout the rooting process. The conjugates were active in inducing rooting of cuttings, with IBAsp being superior to free IBA. It is suggested that IBA conjugates, and particularly IBAsp, serve as the source of auxin during the later stages of rooting.     

Effects of forest soil desiccation on the growth of Eucalyptus regnans F. Muell. seedlings

Abstract. The growth rate of Eucalyptus regnans seedlings in their first year can be much increased if the soil is first dried and then rewetted. The ratio of growth on predried soil to growth on undried soil (the Growth Ratio or GR) reaches a maximum at air-dryness (pF 6.0–6.4). In E. regnans forest soil, GR is greatest in humus-rich topsoil and declines with depth. The effect of air-drying persists for several months after rewetting when soil is stored under glasshouse conditions. It is largely unaffected by repeated drying and wetting, by the rate of drying or by the season of collection. The mixing of dried and undried soil or the placement of a layer of dried soil above undried soil produces an enhancement of growth proportional to the amount of dried soil added. Firing of a litter layer above soil at wilting point increases subsequent seedling growth to that in air-dried soil. The addition of ash from a litter fire to undried soil produces an increase in growth approximately equal to that caused by air-drying The drying effect is most pronounced in soils from mature E. regnans forest and nearby brackenland and is less in dense younger forest, frost-hollow grasslands and old grassy gaps in the mature forest. The effect is restored by the inoculation of E. regnans mycorrhizal roots from both dried and undried soil. The effect varies along an gradient from 500 to 1500 m a.s.l. and is a maximum in the wet E. regnans climatic zone and a minimum in zones or local aspects where forests are normally subject to frequent drying. The stimulatory effect on seedling growth in soils of the E. regnans zone may have an effect on the outcome of competition during regeneration in large gaps. Part of the growth responses previously ascribed to the ‘ash-bed’ effect may be due to the desiccation effect in these soils.     

Occurrence and in Vivo Biosynthesis of Indole-3-Butyric Acid in Corn (Zea mays L.)

Indole-3-butyric acid (IBA) was identified as an endogenous compound in leaves and roots of maize (Zea mays L.) var Inrakorn by thin layer chromatography, high-performance liquid chromatography, and gas chromatography-mass spectrometry. Its presence was also confirmed in the variety Hazera 224. Indole-3-acetic acid (IAA) was metabolized to IBA in vivo by seedlings of the two maize varieties. The reaction product was identified by thin layer chromatography, high performance liquid chromatography, and gas chromatography-mass spectrometry after incubating the corn seedlings with [¹⁴C]IAA and [¹³C₆]IAA. The in vivo conversion of IAA to IBA and the characteristics of IBA formation in two different maize varieties of Zea mays L. (Hazera 224 and Inrakorn) were investigated. IBA-forming activity was examined in the roots, leaves, and coleoptiles of both maize varieties. Whereas in the variety Hazera 224, IBA was formed mostly in the leaves, in the variety Inrakorn, IBA synthesis was detected in the roots as well as in the leaves. A time course study of IBA formation showed that maximum activity was reached in Inrakorn after 1 hour and in Hazera after 2 hours. The pH optimum for the uptake of IAA was 6.0, and that for IBA formation was 7.0. The K_m value for IBA formation was 17 micromolar for Inrakorn and 25 micromolar for Hazera 224. The results are discussed with respect to the possible functions of IBA in the plant.     

杨树试管苗嫩茎生根过程中内源IAA的免疫金银定位

生长素类物质在木本植物生根过程中发挥重要作用。杨树生根与生长素的关系及生根过程中内源激素的变化已有大量报道,而生根过程中生长素的组织定位分析则尚未见报道。该文应用免疫化学分析方法对741杨（Populus alba×（P.davidiana×P.simonii）×P.tomentosa）嫩茎生根过程中内源IAA在组织中的分布进行了研究。结果显示,741杨的嫩茎在无外源激素的1/2MS培养基上诱导10天后可生根,14天后生根率达100%。诱导前,嫩茎基部组织中几乎没有IAA信号;诱导8天后,嫩茎基部维管组织中有大量的IAA积累,而且中部的维管组织中也有明显的IAA信号（主要分布在韧皮部和维管形成层）;10天后,形成不定根原基,此时IAA主要分布在根原基;12天后,根原基分化成不定根并突破表皮,IAA在不定根中的分布主要集中在根尖和中柱。该文对741杨的嫩茎生根过程中IAA的组织分布特点及运输途径进行了讨论。     

杨树试管苗嫩茎生根过程中内源IAA的免疫金银定位

生长素类物质在木本植物生根过程中发挥重要作用。杨树生根与生长素的关系及生根过程中内源激素的变化已有大量报道, 而生根过程中生长素的组织定位分析则尚未见报道。该文应用免疫化学分析方法对741杨(Populus alba × (P. davidiana × P. simonii) × P. tomentosa)嫩茎生根过程中内源IAA在组织中的分布进行了研究。结果显示, 741杨的嫩茎在无外源激素的1/2MS培养基上诱导10天后可生根, 14天后生根率达100%。诱导前, 嫩茎基部组织中几乎没有IAA信号; 诱导8天后, 嫩茎基部维管组织中有大量的IAA积累, 而且中部的维管组织中也有明显的IAA信号(主要分布在韧皮部和维管形成层); 10天后, 形成不定根原基, 此时IAA主要分布在根原基; 12天后, 根原基分化成不定根并突破表皮, IAA在不定根中的分布主要集中在根尖和中柱。该文对741杨的嫩茎生根过程中IAA的组织分布特点及运输途径进行了讨论。     

Studies on the Growth and Indole-3-Acetic Acid and Abscisic Acid Content of Zea mays Seedlings Grown in Microgravity

Measurements were made of the fresh weight, dry weight, dry weight-fresh weight ratio, free and conjugated indole-3-acetic acid, and free and conjugated abscisic acid in seedlings of Zea mays grown in darkness in microgravity and on earth. Imbibition of the dry kernels was for 17 h prior to launch. Growth was for 5 d at ambient orbiter temperature and at a chronic accelerational force of the order of 3 × 10⁻⁵ times earth gravity. Weights and hormone content of the microgravity seedlings were, with minor exceptions, not statistically different from seedlings grown in normal gravity. The tissues of the shuttle-grown plants appeared normal and the seedlings differed only in the lack of orientation of roots and shoots. These findings, based upon 5 d of growth in microgravity, cannot be extrapolated to growth in microgravity for weeks, months, and years, as might occur on a space station. Nonetheless, it is encouraging, for prospects of bioregeneration of the atmosphere and food production in a space station, that no pronounced differences in the parameters measured were apparent during the 5 d of plant seedling growth in microgravity.     

The vestured pits of Eucalyptus regnans F. Muell.: a study using scanning electron microscopy

Scanning electron microscopy has been used to examine the surface architecture, before and after various chemical treatments, of the pits in the walls of vessels, vasicentric and fibre tracheids, and parenchyma cells, which together make up the wood of Eucalyptus regnans. The treatments included water at 150°C under pressure, hydrofluoric acid, delignifying agents and potassium permanganate. All bordered pits were vestured; half-bordered pits were vestured, partially vestured or non-vestured. No distinction could be made between warts and vestures on morphological or chemical grounds. An hypothesis is advanced which relates vesture formation to prolongation of the activity of the protoplast in pits as the cells die. Vestures, on the basis of this hypothesis, could be regarded as enlarged or conglomerate warts.     

Root Development Enhanced by Using Indole-3-butyric Acid and Naphthalene Acetic Acid and Associated Biochemical Changes of In Vitro Azalea Microshoots

Based on the importance of producing in vitro adventitious roots, this study was carried out to investigate the effects of indole-3-butyric acid (IBA) and naphthalene acetic acid (NAA) at a concentration of 2 mg L^?1 on the formation of adventitious roots of azalea and their impact on biochemical changes and endogenous hormones. The rooting percentage, root number, and root length were increased in the microshoots of both studied cultivars (‘Mingchao’ and ‘Zihudie’) when the growth medium was supplemented with IBA. Additionally, peroxidase, indole acetic acid oxidase, hydrogen peroxide, and soluble protein contents were improved in both cultivars by auxin treatments especially during the first 7 days of the rooting period. However, application of IBA and NAA increased catalase and polyphenol oxidase in both cultivars during the first 14 and 28 days of culture. The increase in endogenous indole acetic acid (IAA) levels was accompanied by low activity of IAAO during most periods of root induction of microshoots in all treatments. Endogenous gibberellic acid levels were increased after 7 days of culture and then increased again after 28 days of culture. In contrast, the levels of endogenous zeatin riboside and isopentenyl adenosine were decreased with auxin treatments in the first period of the rooting process and then increased after 21 and 28 days of culture. The present study demonstrated that IBA at a concentration of 2 mg L^?1 has a strong effect on azalea rooting. Moreover, the efficiency of IBA and NAA effects on biochemical changes during adventitious root induction was investigated, which may provide new horizons of in vitro rooting production and provide valuable information for the micropropagation of Rhododendron plants.     

Acid Phosphatase Activity in Karri (Eucalyptus diversicolor F. Muell.) in Relation to Soil Phosphate and Nitrogen Supply

O'Connell, A. M. and Grove, T. S. 1985. Acid phosphatase activityin karri (Eucalyptus diversicolor F. Muell.) in relation tosoil phosphate and nitrogen supply.—J. exp. Bot. 36: 1359–1372 Soluble acid phosphatase activity was measured in tissues ofkarri (Eucalyptus diversicolor F. Muell.) seedlings and fiveyear old karri trees to which P and N fertilizer had been applied.Addition of P from 0 to 1250 mg P kg^–1 soil with a basaltreatment of other nutrients produced significant increasesin growth, P content and P concentration of karri seedlings.In each of five plant components (shoot tips, partly expandedleaves, mature leaves, young stems and old stems) soluble acidphosphatase activity was greatest at low levels of added P anddecreased with increasing soil P supply. The range of acid phosphataseactivity (0·5-6·5 µmol NPP g^–1 f.wt.min^–1) was similar to that reported for a number of agriculturaland horticultural plants. Enzyme activity was highest for shoottips and lowest for old stems. However, the relative changein activity with decreasing soil P supply was greatest for stems(4·3 fold) and least for shoot tips (2·7 fold) Mature leaves of seedlings grown in ‘high P’ and‘low P’ soil at four levels of added N showed, inaddition to the effect of P, a significant N-P interaction onsoluble acid phosphatase activity. In leaf samples from fiveyear old karri trees there was a significant decrease in solubleacid phosphatase with increasing P fertilization. Addition ofN fertilizer had no significant effect on enzyme activity, probablybecause added N had little effect on foliar N concentrations Exponential models relating (1) plant growth to enzyme activityand (2) plant growth to P concentration in stems and matureleaves of plants grown in soil with a range of added P accountedfor 78–92% and 63–87%, respectively, of the variationin top dry weight. The results suggest that for the diagnosisof plant P status, (1) stem components may be the most appropriatetissue to sample, and (2) nutrient and enzyme assays may complementeach other, P concentration being most useful where P supplyis adequate and phosphatase activity where P supply limits growth Key words: Phosphatase activity, Eucalyptus diversicolor, nutrients, phosphorus, nitrogen, forests     

Effects of bacteria on mycorrhizal development and growth of container grown Eucalyptus diversicolor F. Muell. seedlings

The development of ectomycorrhizas on inoculated eucalypt seedlings in commercial nurseries is often slow so that only a small percentage of roots are mycorrhizal at the time of outplanting. If mycorrhizal formation could be enhanced by co-inoculation with bacteria which promote rapid root colonisation by specific ectomycorrhizal fungi, as demonstrated by certain bacteria in the Douglas fir-Laccaria bicolor association, this would be of advantage to the eucalypt forest industry. Two bacterial isolates with a demonstrated Mycorrhization Helper Bacteria (MHB) effect on ectomycorrhiza formation between Pseudotsuga menziesii and Laccaria bicolor (S238), and seven Western Australian bacterial isolates from Laccaria fraterna sporocarps or ectomycorrhizas were tested in isolation for their effect on ectomycorrhizal development by three Laccaria spp. with Eucalyptus diversicolor seedlings. Mycorrhizal formation by L. fraterna (E710) as measured by percentage infected root tips, increased significantly (p < 0.05) by up to 296% in treatments coinoculated with MHB isolates from France (Pseudomonas fluorescens Bbc6 or Bacillus subtilis MB3), or indigenous isolates (Bacillus sp. Elf28 or a pseudomonad Elf29). In treatments coinoculated with L. laccata (E766) and the MHB isolate P. fluorescens (Bbc6) mycorrhizal development was significantly inhibited (p < 0.05). A significant Plant Growth Promoting Rhizobacteria (PGPR) effect was observed where the mean shoot d.w. of seedlings inoculated only with an unidentified bacterium (Elf21), was 49% greater than the mean of uninoculated controls (-fungus, -bacterium). Mean shoot d.w. of seedlings coinoculated with L. bicolor (S-238), which did not form ectomycorrhizas with E. diversicolor, and an unidentified bacterium (Slf14) or Bacillus sp. (Elf28) were significantly higher than uninoculated seedlings or seedlings inoculated with L. bicolor (S-238) alone. This is the first time that an MHB effect has been demonstrated in a eucalypt-ectomycorrhizal fungus association. These organisms have the potential to improve ectomycorrhizal development on eucalypts under nursery conditions and this is particularly important for fast growing eucalypt species where the retention time of seedlings in the nursery is of short duration (2–3 months).