Seed Dormancy in Acer: The Role of Testa-imposed and Embryo Dormancy in Acer velutinum

The embryo dormancy shown in freshly harvested samples of Acervelutinum seeds is weakly established and very short-lived.Loss of this embryo dormancy occurred during post-harvest fruitstorage at either 5 or 17 C. In contrast, the dormancy of intactfruits and seeds was overcome only during storage at the lowertemperature. Removal of the cotyledons from embryos of freshlyharvested fruits allowed more rapid germination of the embryonicaxes, indicating that the cotyledons exert an inhibitory effect,although the axes still retained a measure of innate dormancy.The inhibitory effect of the cotyledons became less marked withincreasing duration of fruit storage, this loss of inhibitoryeffect occurring at both storage temperatures. Applied ABA stronglysuppressed germinative capacity in intact embryos and isolatedembryonic axes from freshly harvested fruits, but when ABA wasapplied to embryos of fruits that had been stored for variousperiods at 5 or 17 C, the inhibitory effect was first weakenedand then lost with increased storage. Although dormancy in the seeds of A. velutinum may be describedas intermediate between testa-imposed dormancy and true dormancy,it is perhaps more properly included in the former category. Acer velutinum Boiss. var. vanvolxemii, abscisic acid, embryo dormancy, germination, seed storage, testa-imposed dormancy, tissue sensitivity     

Endogeneous levels of indole-3-acetic acid and abscisic acid during the rooting of Cotinus coggygria cuttings taken at different times of the year

Cuttings of Cotinus coggyria cv Royal Purple rooted well in the spring but not at all later in the season. Levels of free and conjugated IAA and ABA were measured in cuttings taken at different times of the year. Hormones were measured in the leaf, the upper stem and the lower stem (rooting zone). In cuttings taken in early June the level of IAA was much higher than that of conjugated IAA. In late July the opposite was found. No significant differences in ABA levels were found although the ABA/IAA ratio changed dramatically.     

Interaction of abscisic acid and auxins in rooting of cuttings

Abscisic acid (ABA) at optimum concentrations promoted rootingof Phaseolus aureus ROXB. and Lycopersicon esculentum MILL,stem cuttings. In combination with IAA (indole-3-acetic acid)ABA has mostly given additive effects. Synergistic effect ofABA was noted on IBA (-indolebutyric acid)-induced rooting ofLycopersicon cuttings. Rooting of Phaseolus vulgaris L. cuttingscompletely failed when ABA (50 mg/liter) was applied in combinationwith IBA or NAA (-naphthaleneacetic acid). The results suggestthat abscisic acid may be an important natural regulator ofrooting in cuttings. (Received March 19, 1970; )     

Adventitious Root Formation in Veronica Spp.

Species of the genus Veronica differ in habitat preferences,growth form and in adventitious root production. The annualspecies rarely or never produce adventitious roots in intactplants in the field but some, for example V. persica and V.arvensis will root vigorously from single node stem segmentsin culture. Others, such as V. agrestis require the presenceof IAA for substantial levels of root formation to occur incultured stem segments. Veronica hederifolia cuttings rarelyproduce roots. Stem cuttings of the perennial species, in general,rooted more vigorously than those of annual plants. Both V.fihiformis and V. serpyllifolia root very strongly. The position of root production from the stem cuttings differedfrom species to species. Roots arose either from the node, theregion of the base or at some intermediate point. Veronica arvensis,V. chamaedrys and V. persica rooted mainly from the basal regionwhereas V. filiformis rooted mainly from the node. Veronicaserpyllifolia cuttings rooted at both of these locations. Veronica filiformis, a perennial species that is infertile inBritain, produces root primordia in intact plants at nodes whichare close to the shoot apex. Thus, even very young stem segmentshave ‘preformed’ root primordia. For this reason,detached stem segments of V. filiformis root very rapidly andthis probably has been of great significance in its successfulinvasion and spread in lawns and short turf areas. Veronica spp., adventitious roots, indol-3-ylacetic acid, root primordia, vegetative reproduction     

Bud Dormancy in the Kiwi Fruit, Actinidia chinensis Planch

A study of lateral bud dormancy in Actinidia chinensis has shownthat true dormancy can be induced, especially in short daysat warm and constant temperatures This dormancy can be brokenquantitatively by chilling but temperatures as high as 10 °Care effective The dormancy appears to be due to an inhibitor(possibly ABA), apparently stored in the special bud cover aspecial structure in Kiwi fruit which may represent fused stipulesRemoval of the cover also admits oxygen and light, both of whichhave promoting effects on bud break Application of ABA enhancesdormancy (as do crude extracts tentatively identified as ABA)while GA₃ application enhances dormancy before chilling andpromotes bud break only after chilling Actinidia chinensis, Kiwi fruit, dormancy, abscissic acid, gibberellic acid, chilling     

Synergistic effect of ribose and 2-deoxy-ribose with nutrition and auxin in rooting hypocotyl cuttings of Phaseolus mungo

Exogenously supplied ribose and deoxyribose in a medium containingsucrose+ IAA considerably enhanced the formation of roots onhypocotyl cuttings of Phaseolus mungo with intact apex andleaves.The effect increased with increasing concentration of pentosesugars and was more pronounced with deoxyribose than with ribosesugar. (Received October 25, 1975; )     

Effect of Peroxydisulfate on Vigna radiata Abscission

K₂S₂O₈, applied to the basal end of cuttings of Vigna radiatastimulated leaf abscission in the light or dark. Because inhibitionof leaf sbscission in the dark by IAA was completely abolishedby K₂S₂O₈, and IAA decreased stimulation of abscission by K₂S₂O₈,destruction of IAA in the cuttings by K₂S₂O₈ is indicated. K₂S₂O₈had no effect on leaf abscission when applied as a foliar sprayor when roots of undisturbed seedlings were treated. When appliedproximally or distally to leafless explants, K₂S₂O₈ inhibitedpetiole abscission, and neither IAA nor ethylene had an effecton the inhibition. Although K₂S₂O₈ destroyed IAA in vitro, ithad no effect on abscission inhibitors in macerates of Vignaleaves and corn roots, nor did it destroy the biological activityof IAA added to such macerates. Substances liberated by macerationmay interfere with the ability of K₂S₂O₈ to destroy IAA. (Received May 2, 1981; Accepted August 24, 1981)     

Factors affecting the inhibitory effect of indolylacetic acid on root formation in pea cuttings

Indol-3yl-acetic acid (IAA) present in the rooting solution for 1–4 days appreciably decreased the number of roots subsequently formed in pea stem cuttings. Removal of the lowest 10 mm of the cutting base after IAA treatment abolished the inhibitory effect of IAA almost completely. The number of roots formed from the remaining part of the base internode after excision of the basal centimeter of the internode 4 days after the cuttings were taken was similar to that of the control. It is concluded that the first root primordia, which develop near the cut surface, have an inhibitory influence on development of further roots. The inhibitory effect of IAA may be explained as a strengthening of this dominance phenomenon.
Addition of charcoal to the rooting solution delayed the appearance of roots but increased the number of roots developed during a standard rooting period. Adsorption of stimulatory and inhibitory compounds at the surface of the cutting base is believed to be the reason for these results as no evidence of accumulation of inhibitory compounds in the solution was obtained. Charcoal reversed the inhibitory effect of IAA if added after the IAA treatment. This reversal was almost complete if the IAA treatment lasted for one day only but decreased drastically if the IAA treatment was extended over 4 days.     

Effect of malformin on adventitious root formation and metabolism of indoleacetic acid-2-14C by Phaseolus vulgaris

Malformin inhibited rooting on cuttings of Phaseolus vulgaris.IAA antagonized malformin-induced inhibition of rooting, butmalformin inhibited IAA-induced swelling on the base of thecuttings. It was suggested that IAA-induced swelling was mediatedby ethylene. Malformin did not inhibit transport of root-promotingsubstances from upper portions of the cuttings or polar transportof IAA-2-¹⁴C, nor did it alter the melting point of DNA or thebinding of DNA to histone. Although malformin appeared to alterthe metabolism of IAA-2-¹⁴C, the effect may have been the resultof a marked and selective stimulation of efflux of IAA-2-¹⁴Cmetabolites by malformin. Efflux of IAA or its metabolites maycontribute toward inhibition of rooting by malformin. ¹ Journal Paper No. 4688 of the Purdue Agricultural ExperimentStation. Supported in part by grant GB-7158 from the NationalScience Foundation. ² Present address: Botanisches Institut der Technischen UniversitätBraunschweig, 3300 Braunschweig, Humboldtstraße 1. (Received March 9, 1972; )     

Root Growth Inhibitors from Root Cap and Root Meristem of Zea mays L.

A micro-assay based on the growth inhibition of root segmentsof the seminal roots of Zea mays has been used to investigatethe root-growth-inhibiting substances in root caps and meristemsrespectively of the roots of Zea mays. This micro-assay is sensitiveto 50 pg of IAA or less. Paper chromatography of the acid fractionof methanolic extracts shows the presence of one main inhibitorin root caps and a different main inhibitor in root meristems.Neither is IAA, whose presence in meristems is sometimes indicatedby small inhibitions (or stimulations) at the characteristicRf of IAA. A Commelina leaf-epidermis assay shows the presenceof one stomata-closing ABA-like substance in root caps and onein meristems, one corresponding in Rf to the main root-growthinhibitor from the root cap. The implications of these findingsfor the geotropic responses of roots is briefly discussed.     

Isolation, Purification, and Characterization of an Endogenous Root-promoting Factor Obtained from Basal Sections of Pear Hardwood Cuttings

Basal segments taken from Old Home and Bartlett pear hardwood cuttings collected at intervals during the rooting period in September were extracted with ethanol and fractionated by paper chromatography in different solvent systems. Different zones on the chromatograms were bioassayed by the mung bean rooting test, which showed high levels of promotion in Old Home basal extracts when the cuttings were obtained during the period of maximum rooting. Extracts from Bartlett cuttings, however, showed considerably less promotion activity in the bioassay but did show high levels of inhibitory activity.

After the easily-rooted Old Home cuttings had been in the rooting medium for 10 days, a highly active endogenous root-promoting material was found in extracts from basal segments of cuttings having buds and which had been treated with indolebutyric acid. Similar extracts obtained from disbudded cuttings, or from cuttings with buds but not treated with indolebutyric acid, lacked this rooting-factor. Extracts obtained from all types of the difficult-to-root Bartlett cuttings also lacked this rooting-factor. The latter is believed to be produced by physiologically active Old Home buds, and is very effective in the mung bean bioassay, even at extremely low concentrations.

From paper chromatographic studies, tests with spray reagents, solubility determinations, biological tests, UV spectrum analysis, and infrared spectroscopy, it is believed that this rooting factor could be a condensation product between exogenous auxin (indolebutyric acid) and a phenolic compound produced by physiologically active Old Home pear buds.

     

One-Leaf Cuttings as a Model to Study Second Growth in the Potato (Solanum tuberosum) Plant

Second growth is an important physiological disorder of thepotato (Solanum tuberosum L.) plant. A model system to studysecond growth was developed using one-leaf cuttings. Photoperiod,temperature, decapitation and leaf removal treatments were carriedout on the plants from which the cuttings were taken and onthe cuttings themselves. Tuberized, one-leaf cuttings takenfrom moderately-induced plants and exposed to 35 °C afterleaf removal showed 95% second growth within 10 d after treatmentinitiation. Conditions that promoted second growth also reducedstarch and dry-matter content, even in tubers that did not developsecond growth. Cuttings, second growth, potato, Solanum tuberosum L, cv, Bintje, Solanum tuberosum L. cv., Désirée, Solanum tuberosum L. cv., Russet Burbank, tuberization, starch content, dry-matter, heat, photoperiod, decapitation, leaf removal     

Levels of Endogenous Indole-3-acetic Acid in Achenes of Rosa rugosa during Dormancy Release and Germination

Indole-3-acetic acid (IAA) in highly purified extracts of rose achenes (Rosa rugosa var rubra) was quantified by means of ion-pair reversephase high performance liquid chromatography with spectrofluorimetric detection. Changes in IAA content were determined during a 14-week 4°C stratification, which leads to dormancy breakage, and during subsequent germination at 17°C. IAA was also determined in achenes stratified in parallel at 17°C, which does not induce release from dormancy. IAA decreased during the first 2 weeks of stratification both at 4°C and at 17°C. IAA remained low during the remaining 12 weeks of stratification at 4°C, whereas it continued to decrease in achenes kept at 17°C. An immediate increase in IAA during germination was followed by transients in the IAA level. The results suggest that IAA is without a regulating role in dormancy release although it seems to be involved in the germination process.     

Effects of auxin and gibberellin on conidial germination in Neurospora crassa

Auxins, IAA, 2,4-D, and NAA, and gibberellin, GA, significantlyenhanced the conidial germination rate in the wild-type Neurosporacrassa. The inhibitory effect of an antiauxin, 2,4,6-T on conidialgermination was overcome by IAA. The present results suggestthat auxin and gibberellin may act as regulators of conidialgermination in Neurospora. (Received November 21, 1977; )     

Effect of Indoleacetic Acid on Growth and Dinitrogen Fixation in Cyanobacteria

The effect of IAA on growth, dinitrogen fixation, and heterocystsfrequency of Anabaena PCC 7119 and Nodularia sp. have been investigated.Concentrations of IAA ranging from 10^–10 to 10^–4M did not change the growth of Anabaena PCC 7119. Concentrationshigher than 10^–4 M were inhibitory. Similar results werefound in Nodularia sp. although in this case the inhibitoryeffect appeared with 10^–5M of IAA. Neither the nitrogenaseactivity nor the heterocysts frequency were enhanced by IAAtreatment. (Received June 17, 1986; Accepted January 22, 1987)     

Juvenility and endogenous rooting substances inCastanea sativa Mill

The rooting response to exogenous auxin of cuttings in a juvenile phase of growth from plants ofCastanea sativa Mill. was determined and simultaneously the rooting potential of the water extracts was evaluated in presence of IAA by a bean rooting test. The level of the extractable rooting promoters was high in the cuttings which exhibited the highest percentage of rooting. An inhibition of the effect of IAA on rooting was detected in the cuttings which showed the lowest rooting response, the histogram differing not much from that of the adult plant. The results indicate that in chestnut the juvenile condition, easy rooting, is associated with high levels of endogenous rooting promoters.     

Factors Controlling the Basipetal Pattern of Tuberization in Induced Potato (Solanum tuberosum L.) Cuttings

Potato plants (Solanum tuberosum L. cvs Chippewa and Katahdin)were grown in a glasshouse under continuous light. Various numbersof long (16 h) nights were given to these plants and stem cuttingswere taken. Treatments were applied to the cuttings, which werethen placed in a mist bench under continuous light and examinedfor tuberization after 12 days. The general tendency for the strongest tuberization to occurat the most basipetal nodes, which is commonly seen with intactpotato plants, was also found on stem cuttings. This patterncould not be attributed primarily to orientation with respectto gravity, proximity to the mother tuber, or age of buriedbuds. Buried buds farthest from active leaves tended to tuberizethe most strongly. However, distance of the buried bud fromstem exposed to light may have been of equal or greater importance. potato, Solanum tuberosum L., stem cuttings, tuberization     

Water-related Phenomena in Winter Buds and Twigs of Picea abies L. (Karst.) until Bud-burst: A Biological, Histological and NMR Study

This paper investigates the uptake, transport, state and self-diffusionof water in twigs and buds ofPicea abies L. (Karst.) trees inwinter until reactivation in spring. The presence or absenceof xylem in embryonic shoots, as well as the intensity and typeof bud dormancy were also studied. Three clones of P. abieswere grown in a forest in north-eastern France. The clones differedin their timing of bud-burst, with the two clones from the Vosgesshowing different degrees of early bud-burst and the clone fromPoland showing late bud-burst. One-bud cuttings grown in standardforcing conditions showed a great difference in dormancy betweenthe two provenances, but only a small difference between thetwo Vosges clones. Earliness of bud-burst was not strongly linkedto the intensity of dormancy. A dye experiment combined withlight microscopy indicated increased velocity of water transportin stems up to a maximum in April, initial entry of water intoembryonic shoots, protoxylem differentiation in embryonic shootsfrom April, and then, shortly before bud-burst, water transportthrough the newly-formed protoxylem almost up to the meristem.Nuclear magnetic resonance measurements of the transverse relaxationtime (T₂) and the self-diffusion coefficient of water confirmedthese observations and showed water availability in embryonicshoots. The sequence of water-related phenomena occurring inearly spring was the same in the three clones, but was earliestin the Vosges clone with the earliest bud-burst and latest inthe Polish clone with late bud-burst. The results imply thatthis sequence of water-related phenomena leads to bud-burst.Copyright 2000 Annals of Botany Company Bud, bud-burst, dormancy, embryonic shoot, growth capacity, nuclear magnetic resonance (NMR), Norway spruce,Picea abies L (Karst.), self-diffusion, stem, water, xylem     

The Auxin Content of Root Nodules and Roots of Alnus glutinosa (L.) Vill.

In the acid ether-soluble fraction of methanol extracts of rootnodules and roots of Alnus glutinosa (L.) Vill., indol.3yl .aceticacid (IAA) and indol-3yl-carboxylic acid (ICA) were demonstratedspectroflurometrically and the amounts determined quantitatively.Substantially more IAA was detected in nodule tissue than inroots. No seasonal variation in the IAA content, either forthe roots, could be found. ICA was present in measurable amountsonly in the root extracts. Biochromatographic investigations of the extracts revealed IAAto be the main auxin in the nodule tissues. These findings arediscussed with special attention to results of comparable investigationsof auxins in leguminous root nodules and roots.     

Effect of Non-auxin Chemicals on Translocation of Auxins in Cuttings of Phaseolus vulgaris (L.)

Indole, -naphthol, pyrogallol, coumarin, and salicylic acidinteracted with the auxins, IAA (indol-3yl-acetic acid), NAA(naphth-lyl-acetic acid), and 2, 4-D (2, 4-dichlorophenoxyaceticacid), supplied to the basal ends of cuttings of Phaseolus vulgaris(L.), giving synergistic or antagonistic effects in root formation.Antagonism in rooting was always associated with increased accumulationof radiocarbon from carboxyl-¹⁴C-labelled auxins in the topsof the cuttings. Distribution of auxin over a greater lengthof the cutting was accompanied by a reduction in root formation.The chemicals which synergized auxin-induced root formationdid not promote accumulation of radiocarbon of the exogenouslyapplied labelled auxins in the upper parts of the cuttings.