Growth-Regulating Substances and the Growth of Tiller Buds in Barley; Effects of IAA and GA3

Application of cytokinin to barley seedlings grown without mineralnutrients leads to rapid growth of coleoptile and first leaftiller buds. IAA and GA₃ cannot substitute for cytokinin inthis effect and applications of TIBA and CCC are also ineffectiveon bud growth. However, when bud growth was promoted, eitherby application of cytokinins or by supplying plants with mineralnutrients, IAA and GA₃ applications caused enhanced tiller growthindicating that these compounds can stimulate growth of activelygrowing buds. The results are compatible with an interpretationwhich stresses the importance of cytokinin availability in determiningtiller bud growth.     

Growth of Tiller Buds in Barley: Effects of Shade Treatment and Mineral Nutrition

Examination of the stem apex of Proctor barley showed that thebud of the coleoptile tiller, Tc, is probably present in thedry grain and that the bud, TI, carried in the axil of the firstleaf is present at or soon after 24 h from planting. Subsequentlytiller buds are initiated with a plastochron of about 4 days,this being rather longer than that for the foliar primordia.During the initial phase of bud growth vascular connectionsare established with the leaf above, but not to the subtendingleaf. At some time after these vascular connections are formedand when it has a dry weight of 4–7 µg the bud entersa phase of rapid, exponential growth in dry weight. Shading the first leaf delays the onset of rapid growth forboth Tc and Ti, but after a lag period rapid growth commences;this is coincident with development of the second leaf as anorgan exporting assimilated carbon. The phase of rapid growth of tiller buds is delayed when applicationof either nitrogenous or nonnitrogenous minerals is delayed.Ammonium was found to be less satisfactory as a nitrogen sourcethan nitrate, probably because of toxicity effects. Slight growthof Tc and T1 occurs in presence of nonnitrogenous minerals andabsence of nitrogen but growth is greater when nitrogen is suppliedin absence of the other minerals, although such growth is substantiallyless than that found when all nutrients are supplied. The interactionbetween nitrogen and non-nitrogenous minerals which controlsbud growth was not found to affect growth of the parent plantwhich is, as previously shown, controlled by timing of the nitrogensupply. AnotheT distinction is that higher concentrations ofnitrogen and the other minerals are required for maximum growthof the bud than for that of the plant. Tiller bud growth is interpreted as occurring in two phases.In the first, initiation, phase there is a close associationwith the subtending leaf, and nutritionally bud and leaf arelinked. This phase is followed by one in which the bud is directlyconnected by vascular traces to the leaf above, which becauseof this controls bud growth by modulating supply of assimilatedcarbon and nitrogen, and other minerals to it.     

A Comparison of Main-stem and Tiller Growth in Barley; Apical Development and Leaf-unfolding Rates

Information is presented on the hierarchical relationship betweenthe stems of Proctor barley grown under controlled conditions.Rates of production of foliar and floral primordia and ratesof leaf unfolding were found to follow the order main-stem >primary tillers > secondary tillers. Apical dome size wasinitially substantially greater for the main-stem than for thetillers due principally to the slower transition of the latterto the reproductive condition; by the time that double ridgesare formed on the tiller apices apical dome sizes are similarto that of the main-stem. Transition to the reproductive conditionoccurs at about the same time for the primary tillers. Thisnear-synchrony results in a smaller number of leaves borne onsuccessive tillers, since these have had less time to initiatefoliar primordia, and a measure of synchrony in awn appearance,since rates of car development are similar for these stems. The nature of the hierarchical relationship between main-stemand tillers is discussed.     

Cytokinins in Vegetative and Reproductive Buds of Pseudotsuga menziesii

Immunoaffinity techniques using columns of immobilized antibodies raised against zeatin riboside and isopentenyladenosine were found to be effective in isolating cytoklnins from vegetative, female, and male buds of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco). The purified cytokinins were separated by reverse phase high performance liquid chromatography and analyzed by radioimmunoassay. Confirmation of cytokinin identities was by gas chromatography-mass spectrometry. Immediately prior to bud burst, all bud types contained three major cytokinins: isopentenyladenosine, zeatin riboside, and a hexose conjugate of zeatin riboside (not zeatin riboside O-glucoside). Zeatin-type cytokinins were present in relatively high concentration in vegetative and female buds. In male buds, however, relatively high levels of isopentenyladenosine were found together with low levels of zeatin-type cytokinins.     

Investigations into the Possibility that Potato Buds Synthesize Cytokinins

In an attempt to determine whether potato buds synthesize cytokinins,tubers and potato pieces were subjected to conditions whichboth retard and accelerate bud development. Cytokinin activitywas recorded in the tubers and sprouts under different experimentalconditions. Most of the compounds detected had chromatographicproperties resembling those of zeatin, zeatin riboside, andzeatin glucoside. It would appear as if the buds and sproutsdo not synthesize cytokinins. Initial bud growth may be dependenton the supply of cytokinins within the mother tubers, whilethe increase in the sprouts could be the result of root developmentat their basal ends.     

生长调节物质和可溶性糖含量对丹参中丹酚酸类物质积累的影响

采用盆栽实验研究了生长调节物质水杨酸（SA）、茉莉酸甲酯（MeJA）、赤霉素（GA3）对不同生长时期丹参植株中非结构糖含量、碳/氮比及根中丹酚酸类物质积累的影响;并进一步测定培养基中不同浓度蔗糖、葡萄糖、果糖对丹参毛状根中丹酚酸类物质积累的影响,对盆栽实验的结论进行了验证。结果显示,SA处理的丹参幼苗及花后期植株中蔗糖含量有增加趋势,而MeJA处理的丹参幼苗及花后期植株及GA3处理的丹参花后期植株中蔗糖积累均有降低趋势;且SA、MeJA和GA3处理对花后期植株地上和地下部分碳/氮比的影响不同。然而,SA和MeJA处理的丹参幼苗及花后期植株地上部分和根中还原糖含量、GA3处理的花后期植株根中还原糖含量均显著增加;同时,SA和MeJA处理的丹参幼苗根中迷迭香酸含量,以及SA、MeJA、GA3处理的花后期植株根中迷迭香酸含量和丹酚酸类总量显著增加。毛状根培养结果进一步证明,葡萄糖促进毛状根中迷迭香酸的产生,增加丹酚酸类总量,毛状根中迷迭香酸、丹酚酸B的积累及丹酚酸类总量与培养基中蔗糖浓度不相关。可见,丹参（植株）根中丹酚酸类物质的产生和积累受SA、MeJA和GA3的诱导,其与碳/氮比及植株中蔗糖含量没有相关性,推测植株中葡萄糖含量的增加促进根中丹酚酸类物质的积累。     

Effects of Nutrient Factors, Water-Supply, and Growth-Regulating Substances on the Vegetative Growth Pattern of Peas and their Relationship to the Node of First Flower

Peas were grown at two levels each of nutrient- and water-supply:some were pretreated with gibberellic acid (GA), N-dimethylaminosuccinamicacid (B995), or N-formylhydroxyaminoacetic acid (NFHAA). Alltreatments had some effect on internode extension and leaf growth.B995 and NFHAA acted as general inhibitors of growth, ratherthan suppressing growth of particular organs: their effect inlowering the number of the first flowering node (F) might berelated to this inhibition. Water-supply had a greater effecton the rate of node formation than had nutrient-supply, B995,or NFHAA, but had no effect on F: in this case there is no clearrelationship between vegetative growth and flowering. Theseresults are briefly discussed in relation to earlier work.     

Elicitor–like Substances Present in Barley and Wheat Seeds

Abstract Barley and wheat seeds contain elicitor–like substances which induce the production of antifungal substances in the host plants effective against powdery mildew fungi. Seed extract per se does not exhibit direct antimicrobial activity but induces the resistance response on the host. It also induces the systemic resistance in juvenile leaves. Host resistance induced by the treatment with seed extract shows some degree of cultivar specificity.     

Changes in Cytokinins and Gibberellin-Like Substances in Pinus radiata Buds during Lateral Shoot Initiation and the Characterization of Ribosyl Zeatin and a Novel Ribosyl Zeatin Glycoside

Based on detection and quantitation by bioassay, endogenous gibberellin-like substances (GAs) and cytokinins (CKs) in Pinus radiata D. Don buds during sequential shoot initiation shift from less polar to more polar forms (GAs) and from conjugated to free forms (CKs). As the terminal bud moves from the production of “short shoots” (needle fascicles) to “long shoots” (lateral branches or female conebuds), a more polar GA appears while a glucoside-conjugate of zeatin riboside is reduced, and zeatin riboside levels increase markedly.     

Effects of Cytokinins on the Growth of Primary Roots of Zea mays

Intact primary roots of Zea mays seedlings, apical 6-mm segmentsisolated from the intact primary roots and 5-mm detipped segments,prepared from the 6-mm apical segments by removal of the apical1-mm meristematic region, were incubated in potassium-phosphatebuffer that contained various concentrations of kinetin, 6-benzylaminopurine(BAP) or zeatin. These cytokinins inhibited the growth of intactprimary roots but they promoted the growth of both tipped anddetipped apical segments. In other words, they promoted thegrowth of root segments irrespective of the presence or absenceof apical meristematic regions. Detipped segments were stoodvertically, with their apical or basal cutends in contact withan agar plate that contained the abovementioned buffer and variousconcentrations of kinetin, BAP or zeatin so that cytokininswere supplied either from the apical or basal cut-ends. Cytokininssupplied from the top promoted the growth of the segments, whilethose supplied from the base did not. These results indicate that the response of roots to the exogenouslyapplied cytokinins is not influenced by the presence of theroot meristem but is significantly affected by the way in whichcytokinins are supplied. (Received October 17, 1995; Accepted August 28, 1995)     

激素对水稻分蘖芽生长和分蘖相关基因表达的调控效应

以水稻品种‘南粳44＇为材料,研究了植物激素对水稻分蘖芽生长及OsTB1、OsD3、OsD10和OsD27等基因表达的调控。结果表明,水稻分蘖芽生长的调控至少存在两条途径,一条通过调控分蘖芽中CTK含量进而调控OsTB1等基因表达来实现,另一条通过调控OsD3、OsD10和OsD27等系列基因表达来实现。外源IAA和GA_3对水稻分蘖芽生长的调控是通过这两条途径共同实现的。     

Changes in the Endogenous Cytokinins of Bark and Buds ofSalix babylonica as a Result of Stem Girdling

Girdling of 1-year-old Salix babyionica L. plants resulted in an early accumulation of compounds which co-chromatographed with cytokinin glucosides in both the bark and buds below the girdle. In the bark the cytokinin glucosides were present in high levels in both girdled and non-girdled plants. In the buds of non-girdled plants. however, glucoside concentration was initially low but then increased rapidly after ringing and reached a maximum level prior to any visible signs of bud swell. With the onset of lateral shoot growth the glucoside cytokinins decreased while the cytokinins that co-chromatographed with zeatin and its derivatives increased. As the cytokinin glucosides are generally considered to be storage forms, their accumulation in the bark and buds below the girdle apparently does not reflect synthesis but rather transport towards a more competitive sink. In the case of Salix plants the lateral buds would appear to have the ability to hydrolyze these glucosylated zeatin derivatives and then to utilize them for bud development. It is suggested that in the presence of a functional root system lateral buds do not synthesize cytokinins de novo, but that they do have the metabolic capacity to convert cytokinins transported to them.     

Interactions in the Physiological Effects of Growth Substances on Plant Development

The interrelated effects of 3-indolylacetic acid and sodium2 : 4-dichlorophenoxyacetate on the growth and development ofLemna minor and Helianthus annuus have been investigated bymeans of multifactorial experiments, involving three to fivelevels of each compound. A clonal population of L. minor wasmaintained under constant conditions of light (550 foot-candles)and temperature (25 C.) and the growth regulators were addedto a phosphate-buffered culture solution (pH 51), which waschanged every 2 days. In the H. annuus experiments the compounds,in aqueous solution, were placed by means of a micro-pipetteon the leaves of young plants grown in a greenhouse or in theopen. Indolylacetic acid, at concentrations up to 25 p.p.m., increasesthe relative growth rate of L. minor on either a dry-weightor frond-area basis. Sodium dichlorophenoxyacetate at 0025p.p.m. has little effect on growth, but at and above concentrationsof 02 p.p.m. growth is depressed. The ratio of frond area tototal dry weight is increased by indolylacetic acid but is depressedby the phenoxyacetate. In the presence of indolylacetic acid,more particularly at the higher levels, the relative inhibitionof growth caused by sodium dichlorophenoxyacetate is reduced. When sunflowers are treated daily with indolylacetic acid (0,6, 30, 150 µg./ plant) or initially with sodium dichlorophenoxyacetate(0, 20, 100 µ.g./plant) in all possible combinations,then the relative growth rates of the treated leaves, the leavesabove the treated leaves, the first internode, and the rootsare depressed when each compound is applied alone. On the otherhand, the growth rate of the hypocotyl is increased by bothgrowth regulators, while for the second internode indolylaceticacid decreases the growth rate but the phenoxyacetate at thelower level accelerates it. The combined action of the two compoundson the different parts tends to be cumulative, save for thehypocotyl, where the effect of indolylacetic acid is dependenton the level of the phenoxyacetate. It is concluded that these results cannot be explained on theconcept of wholly additive effects. There is evidence that thecompounds can mutually interfere in their actions and it wouldseem that more than one mechanism is involved. Many of the resultscan be satisfactorily interpreted on the basis that the twocompounds act on a common system and that they compete withone another, but the results are not compatible with the postulatethat the dichlorophenoxyacetic acid directly inactivates indolylaceticacid.     

Effects of Tiller Separation and Root Pruning on the Growth of Lolium perenne L.

Experiments have been carried out to assess the role of inter-tillerinteractions within plants of Lolium perenne L. cv. S24 as factorswhich could play a part in determining the growth-rate of thewhole plant. In order to do this, the effect of tiller separationon plant growth was studied as well as the influence of theremoval of different parts of the root and shoot system. Wheneverplants were supplied with nutrients by means of culture solutions,separation of tillers brought about a marked increase in theamount of dry matter produced. Root pruning and in particularthe removal of root apices brought about similar increases ingrowth. Separation of tillers in soil-grown plants did not bringabout increased growth. These results are interpreted as indicatingthat separation of tillers or the initial removal of root apicesin plants supplied with nutrients by means of culture solution,promotes root branching which brings about an increased netassimilation rate arising from an increase supply of a growth-promotingsubstance, probably a cytokinin, from the root apices. The resultsare not taken as indicative of an intertiller interaction whichrestricts the growth of intact plants.     

Gibberellin like Substances in Parts of Developing Barley Grain

In husks, the activity of gibberellin-like substances extracted with aqueous methanol (M-“free” GAs) showed a maximum on the 9th day after pollination. In developing embryos, M-“free” GAs showed no biological activity, whereas biological active component(s) were obtained when the embryos were extracted with Tris buffer. The “free” GAs found in the buffer homogenates (B-“free” GAs) of developing embryos showed a maximum of activity on the 33rd day after pollination. Bound GAs recovered from the precipitated protein of the buffer homogenate (“Protein-bound” GAs) were found in embryo and endosperm. Developing endosperm generally contains the major amount of the extractable gibberellin-like substances. In this tissue, the amount of all examined fractions (M-“free” GAs, B-“free” GAs and “protein-bound” GAs) increased after pollination to reach a maximum on the 21st day, before decreasing to a minimum at grain maturity. Moreover, the curves for dry weight increase and gibberellin like substances follow a remarkably similar course, with the latter reaching its maximim slightly earlier than the former one. This result indicates that gibberellines may participate in the regulation of the accumulation process in the endosperm of barley grain.