Resemblance of growth substances to metal chelators with respect to their actions on duckweed growth

Action patterns of IAA, KIN and GA on the growth of Lemna gibbaG3 are similar to those reported for agents chelating both cupricand ferric ions. Relatively high doses of growth substances,e.g.10^–6 M IAA or KIN and ^–4 M GA, inhibit developmentof photoperiodically induced flower buds and antagonisticallypromote frond multiplication; whereas, at relatively low doses,e.g. 10^–9 M IAA or KIN and ^–5 M GA, they acceleratethe process occurring in the latter half of the induction periodto enhance flower induction. Complex forming abilities of IAA,KIN and GA with cupric and ferric ions are demonstrated spectrophotometrically.Moreover, the ferrous ion-dependent oscillatory change in reproductiveand vegetative photophilies of duckweed is eliminated by KINbut not by IAA and GA. Of the three growth substances tried,KIN alone shows an affinity for ferrous ions. (Received April 5, 1971; )     

LIGHT- AND DARK-GROWTH IN LONG-DAY DUCKWEED, LEMNA GIBBA G3, AS AFFECTED BY KINETIN

Under short-day conditions the growth or the production of fronds in Lemna gibba G3 was stimulated by KIN (10^–5 M);the longer the nyctoperiod, the greater the stimulation was.Under long-day conditions KIN was slightly inhibitory for thefirst 2 days, but promotive thereafter. IAA (10^–5 M) reversedthe growth inhibition by KIN in long-days, and DCA (10^–4to 10^–6 M) and also CA (10^–4 to 10^–6 M), althoughless effectively, cancelled the growth promotion by KIN in short-days.DCA (10^–5 M) little altered the KIN inhibition in thefirst 2 days of light culture, nevertheless it alleviated strikinglythe KIN promotion in the subsequent illuminated days. These and relevant findings explained the above-described promotionand inhibition by KIN of the duckweed growth in terms of invivo level of a cofactor (probably auxin) which may be underthe regulative influence of photoperiodic conditions given.Moreover, some bearing of the above conclusion on floweringmechanism in this long-day duck-weed was suggested. (Received September 12, 1966; )     

B-Nine Reversal of Benzimidazole-or IAA-induced Inhibition of Growth and Yield of Cowpea Plants

Growth, flowering, and yield of Cowpea (Vigna catjang) wereinhibited by Benzimidazole (10^-3M) or IAA (10^-2M). These growthinhibitions were reversed by B-Nine (2x10^-3M) which alone waswithout any effect. In combination, IAA and Benzimidazole weremutually antagonistic. A common mechanism is suggested for theB-Nine reversal of the Benzimidazole or IAA inhibition of growth.     

Floral Induction in Wolffia microscopica by Salicylic Acid and Related Compounds under Non-inductive Long Days

Flowering in Wolffia microscopica, a short-day plant, couldbe induced with salicylic acid (SA), under long days. Aspirin,benzoic acid and salicylaldoxime were also effective for inductionof flowering in this duckweed. Amonsgt these, SA is the mosteffective compound, as it could induce flowering even at 10^–7M. Flowering was further enhanced when Wolffia fronds were subjectedto short days, in the presence of SA. However, SA neither showedany effect on flowering ofW. microscopica in the absence ofEDTA in the nutrient medium, nor could it, by itself, supporteven the vegetative growth. The probable mechanism of actionof SA has also been discussed. It appears that the effect cannotbe due simply to chelation of metal ions and perhaps the salicylmoiety itself exerts a specific effect. (Received March 15, 1983; Accepted May 6, 1983)     

Levels of IAA, Cytokinins, ABA and Ethylene in Rice Plants as Affected by a Gibberellin Biosynthesis Inhibitor, Uniconazole-P.

Effects of uniconazole-P, a triazole-type growth retardant,on endogenous levels of IAA, cytokinins, ABA and ethylene inrice seedlings were investigated. Endogenous levels of IAA andABA were similar between control and uniconazole-P-treated riceshoots. Evolution of ethylene was promoted slightly, being 1.8times greater under 0.3 ppm uniconazole-P treatment than thatof control. The most obvious effect was the increase of trans-Zand trans-RZ in shoots. Shoots treated with uniconazole-P (10mg/m² nursery box) contained 3.4 times and 3 times more trans-Zand trans-RZ than control, respectively. No significant differencesof cytokinin levels were recognized in roots except for cis-RZ.The increase of ethylene and active forms of cytokinins, andthe decrease of gibberellin in the shoots may be the basis forphysiological phenomena caused by uniconazole-P, namely thepromotion of flowering in woody plants and the enhancement offemaleness in cucumber. (Received September 9, 1987; Accepted October 20, 1987)     

A Comparative Study of the Effects of Some Growth Regulators on the Biochemistry of Oryza sativa L.

A comparative study was made on the effects of indol-3yl-aceticacid (IAA), maleic hydrazide (MH), naphthalene acetic acid (NAA),and gibberellic acid (GA) at a concentration of 1o^-1 mg I^-1,on the growth and metabolism of Oryza sativa L., cv. Bhasamanik.All the growth substances excepting NAA caused promotion ofroot elongation and increased the number of roots formed buthad very little effect on shoot growth. NAA was found to havea retarding effect on the general growth of the plant, but alsoincreased the number of roots formed. At the concentration used IAA caused enhanced protein synthesisin parallel with increased root growth. However, with MH nosuch direct relationship could be observed between root growthand protein synthesis at the early stage, but stimulation ofroot growth was directly related to increased protein synthesisat the later stage. Despite the adverse effect of NAA on thegrowth of the plant, protein synthesis was not affected. Infact a general increase in the protein content of the plantwas observed. In plants treated with GA increased sugar contentand enhanced protein synthesis were noted. The levels of free amino acids were found to be affected markedlyby the application of the growth regulators. With NAA treatmentan accumulation of asparagine in the shoot and with GA an increasein the level of alanine in the root were noted. Aspartic aciddecreased in the roots, but increased in the shoots of treatedplants. Glutamic acid was lower in plants treated with IAA,MH, and NAA, while treatment with GA increased it in the shootat the tillering stage. In the shoots of IAA-, MH-, and NAA-treatedplants an increase in the quantity of serine was noted whereasunder the action of GA both serine and glycine decreased.     

Uptake of uridine by a long-day duckweed, Lemna gibba G3

Uptake of uridine by a long-day duckweed, Lemna gibba G₃ wasexamined. Km and Vmax for uptake were in the range of 1 to 2x10^–5 M and of 5 to 10 x10^–8 moles/g fresh weight/2hr, respectively. Uptake rate depended on temperature, and theoptimum pH was 5.0. Uridine uptake was competitively inhibitedby some compounds structurally analogous to uridine. However,the activity of uridine kinase was not affected by these compounds,except for cytidine. Uridine uptake was inhibited by metabolicinhibitors, in which uridine taken up was left unconverted toother forms, especially in the presence of DNP. These resultssuggest that uridine was taken up into the duckweed celb bya specific transport system and immediately phosphorylated byuridine kinase. Phosphorylation of uridine was not associatedwith the uridine transport reaction. (Received November 15, 1976; )     

A possible mechanism for sugar inhibition of duckweed flowering

Sugar (ca. 1%) reduced the floral index in Lemna gibba G3 byca. 50%, and supplemental addition of cyclic AMP (ca. 10^–5M)removed nearly all of this sugar action. Inhibition by sugarof duckweed flowering may be explained in terms of cataboliterepression. (Received October 9, 1971; )     

Induction of Flowering in a Duckweed, Wolffia microscopica, under Non-inductive Long Days, by 8-Hydroxyquinoline

Wolffia microscopica, a duckweed, flowers in response to a singlephotoinductive SD cycle of 16 h dark and 8 h light. Floweringin W. microscopica could be induced, under non-inductive longdays, by 8-hydroxyquinoline (8-HQ). Flowering was initiatedwith 10^–6 M 8-HQ and maximum flowering (ca. 75%) was obtainedat 5 x 10^–6M level. Flowering was accentuated furtherwhen plants, supplied with 8-HQ, were subjected to SD cycles. (Received September 13, 1985; Accepted December 4, 1985)     

Floral Induction in a Photoperiodically Neutral Duckweed, Lemna paucicostata Strain LP6: Role of Chelating Agents and Iron

Lemna paucicostata, strain LP₆, does not ordinarily flower underany photoperiodic schedule, when grown in the modified Bonner-Devirianmedium supplemented with 10^–4 M EDTA and 1% sucrose (thisis a medium which is otherwise satisfactory for short day inductionof flowering of other strains of this duckweed). However, when the ferric citrate concentration in the culturemedium containing EDTA was raised 10-fold over that in the normalmedium, a low but significant flowering could be initiated inthis duckweed, irrespective of the length of the photoperiod.A similar flowering response was obtained when ferric citratewas replaced by ferrous sulphate or ferric chloride, therebyindicating that the inductive effect of higher level of ferriccitrate on flowering in strain LP₆ is due to its iron component. Some flowering in this strain could be induced even in mediumcontaining normal level of iron, provided the level of EDTA,itself, was raised to 5?10^–4 (5% flowering) or to 10^–3M (12% flowering), but replacement of EDTA by EDDHA led to trulyremarkable effects. With EDDHA, flowering could be induced at very high levels (90%)under all photoperiodic regimes tried. Floral initiation couldbe obtained even with 10^–6 M EDDHA, though the optimallevel ranged from 5?10^–6 to 10^–5 M. (Received October 4, 1985; Accepted June 26, 1986)     

Some effects of salicylic acid on growth and flowering in Spirodela polyrrhiza SP20

More than 70% flowering was observed in Spirodela polyrrhizaSP₂₀ under long and short days, when fronds were grown in amedium supplemented with 5x10^–5 M salicylate (SA). Toour knowledge this is the first report of such profuse floweringof this duckweed in vitro. Besides flowering, SA also affectedthe multiplication rate, anthocyanin and chlorophyll contents,and gibbosity. Aspirin had an effect similar to that of SA. (Received April 1, 1980; )     

Auxin, transport and growth in intact roots of Vicia faba

Transport of IAA applied to the intact root of Vicia seedlingswas investigated in relation to root growth. The root was treatedat 3–4, 4–5 or 7–8 mm from the tip with anarrow ring of lanolin paste containing IAA or IAA-2-¹⁴C ingrowth or transport experiments, respectively. The growth processalong the root axis was examined in every 1-mm part from thetip at 30 min, 1 or 4 hr intervals. The elongation zone of thecontrol root was 1–9 mm from the tip. IAA treatment broughtabout no significant change in the growth of the region apicalto the treated site, whereas distinct inhibition of growth occurredin the region basal to the treated site within 1 hr. The transportof radioactivity was observed in both acropetal and basipetaldirections within 1 hr, but the latter predominated for 8 hror more; the nearer to the tip the treatment site, the longerthe predominance lasted. The velocities of acropetal and basipetaltransport were estimated at about 4 and 8 mm/hr, respectively.Autoradiographs of transverse section of roots showed that basipetaltransport occurred mainly through the outer part of the root,whereas acropetal transport occurred mainly through the innerpart, the central cylinder. It may be concluded that the basipetallytransported IAA which passed through the outer part of the rootinhibited the elongation of the intact root. (Received November 25, 1975; )     

Polar transport and content of indole-3-acetic acid in wounded sweet potato root tissues

In roots of sweet potato (Ipomoea batatas Lam. cv. Kokei 14),the metabolic response to wounding was remarkable in the proximalside and developed in the acropetal direction. We assumed thatthe polarity resulted from the increase in polar movement ofindoleacetic acid (IAA) (1977, Plant Physiol. 60: 563–566).Transport of IAA and change of the IAA level in the woundedtissue of sweet potato roots were investigated. Transport ofthe label from ¹⁴C-IAA was obviously polarized in the acropetaldirection. ¹⁴C-IAA administered to the wounded tissue was mainlymetabolized into two conjugates of IAA. The amount of IAA inthe wounded tissue, determined by the spectrofluorometric method,increased about 3-fold after 18 hr of incubation prior to thedevelopment of activities of some enzymes. The increase in IAAcontent was not affected with aseptic incubation, therefore,the possibility of IAA production by microorganisms on the woundedtissue was excluded. The results obtained strongly support ourhypothesis that IAA plays an important role in the metabolicresponse to wounding. (Received May 2, 1979; )     

Changes in Endogenous Ribosyl-trans-zeatin and IAA Levels in Relation to the Proliferation of Tobacco Crown Gall Cells

Changes in the contents of major endogenous plant hormones intobacco crown gall cells, namely IAA and ribosyl-trans-zeatin,during cell growth were examined using HPLC and ¹⁴C-labeledplant hormones. The content of IAA was high at the early logarithmicstage, while that of ribosyl-trans-zeatin was high at the middlelogarithmic stage. This suggests that cell growth is affectedfirst by IAA, then by ribosyl-trans-zeatin. ³ Present address: Department of Agricultural Chemistry, TottoriUniversity, Koyama, Tottori 680, Japan (Received July 13, 1981; Accepted September 11, 1981)     

Responses of normal and dwarf Pharbitis nil to an extended dark period and gibberellic acid

The effects of a 24 hr short day, a 24 hr long day, and a 48hr short day were analyzed with regard to flowering and stemgrowth of normal and dwarf Pharbitis nil, and were comparedto effects of these photoperiodic treatments plus applied GA₃.Both short day treatments produced the same number of flowersper plant after seven cycles. The applied GA₃ was effectivein overcoming the growth deficiency of the dwarf; however, theextended dark period of the 48 hr short day and applied GA₃were both required to enhance a flowering response in the dwarfequal to that of the normal. These results indicate that somefactor is present during the extended dark period which enhancesflowering. ¹ This work was supported by NSF Grant GB-7510 and State supportedresearch TTU-191-4771 to M. W. C. ² Present address: Department of Biology, Union University,Jackson, TN 38301, U.S.A. (Received September 4, 1979; )     

EVIDENCE ON THE SITE OF ACTION OF GROWTH RETARDANTS

1. The ability of five growth retardants to inhibit the GA-inducedand endogenous growth of Avena leaf sections has been investigated.The retardants vary in effectiveness. The order, from most effectiveto least, is Phosfon D, Amo-1618, C011, CCC and B995. 2. The inhibition of growth caused by Phosfon D and Amo-1618is not reversed by GA. It is apparent that the retardants donot compete with GA at the site of GA-action. 3. Addition of IAA will partially reverse the inhibition inducedby Phosfon D or Amo-1618. It is concluded that the retardantsact in part in Avena leaf sections by interfering with the auxinmetabolism of the tisssue. ¹ Supported in part by grants G-14578 and GB-1950 from the NationalScience Foundation ² Present address: Department of Botany, University of Washington,Seattle, Washington     

In Vitro Phosphorylation of Proteins in IAA-Treated Mesocotyls in Zea mays

Five-mm sections of elongation zones of Zea mesocotyls wereincubated for designated periods with various concentrationsof IAA. In vitro protein phosphorylation in the soluble fraction(85,000 x g supernatant) prepared from the sections was analyzedby sodium dodecyl sulfate-polyacrylamide gel electrophoresis.The phosphorylation of proteins in the soluble fraction thathad been prepared from sections incubated for 20 min in thepresence of 10{small tilde}^s M IAA was greater than that inthe sections incubated for 20 min without IAA. The amount ofphosphorylation of proteins per protein became higher when higherconcentrations increased (10{small tilde}⁸—10{small tilde}⁵M).The growth of sections incubated in the presence of 10{smalltilde}⁸ M IAA or higher concentrations was greater than thatof sections incubated in the absence of IAA. The promotion ofgrowth by IAA was greater at higher concentrations of IAA. Proteinsin the soluble fraction, prepared from sections incubated for20 min in the presence of 10{small tilde}⁵ M IAA, were phosphorylatedin the presence of either 10 fM cAMP, 10 µM cGMP, 100µM W-7, 100 µM W-5, 20 µM H-7 or 20 µMHA1004. The calmodulin antagonist, W-7, and the inhibitor ofprotein kinase C, H-7, inhibited the phosphorylation of proteinsstimulated by incubation with IAA. These results suggest thatIAA promotes cell elongation via protein phosphorylation thatdepends on calmodulin-dependent protein kinase and protein kinaseC. (Received November 29, 1995; Accepted May 20, 1996)     

Distribution of Radioactivity from Exogenously Supplied [1-14C]Indol-3-yl-acetic Acid and [3, 4-3H (N)] Gibberellin A, in Geotropically-stimulated Picea abies (L.) Karst. Roots

The distribution of exogenously-supplied radioactive labelledindol-3-yl-acetic acid (IAA) and gibberellin A₁ (GA₁) in geotropicallystimulated roots of Norway spruce (Picea abies (L.) Karst.)has been demonstrated. Seedlings were positioned with theirroot tips in 2.1 x 10^–6 M [¹⁴C]IAA or 1.3 x 10^–8m ³H-GA₁ for 4 and 20 h, respectively. After geotropic stimulationfor 90 min in the horizontal position the root tips were cutlongitudinally in 50 µm thick sections, using a freeze-microtome.The radioactivity in the ¹⁴C-IAA treated roots occurred in higherconcentration in the lower than in the upper halves (ratio 1.25:1). A similar trend was observed in the [³H]GA₁-treated rootswhere the ratio lower: upper halves was 2.04: 1. The ratio ofradioactivity in right and left halves of vertical roots wasapproximately the same in roots supplied with [¹⁴C]IAA and [³H]GA₁(1.09: 1). The supplied radioactive compounds were analysed chromatographicallyafter extraction in methanol of 6 mm apical root segments. Onlya small fraction (7–8 per cent) of the supplied [¹⁴C]IAAwas revealed unchanged in the segments. The major part of thechromatographed, labelled compound has not been identified,but on basis of its R_F value it is suggested that it may beindol-3-acetyl-aspartic acid (IAAasp). The chromatographic analysis of the [³H]GA,-treated segmentsshowed that only small fractions of this gibberellin has beenconverted to other compounds. These results have been discussed and correlated with knowledgeof plant growth regulators and their participation in root geotropism. Picea abies, spruce, geotropism, gibberellin A₁, indol-3-yl-acetic acid, growth regulators, redistribution in roots     

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)     

Hormone-directed Transport of Assimilates in Decapitated Internodes of Phaseolus vulgaris L.

Application of ethylene, indole-3yl-acetic acid (IAA), 6-(benzylamino)-9-(2tetrahydropyranyl)-9-Hpurine (SD8339), or mixtures of IAA, gibberellic acid (GA),and cytokinins, increased the accumulation of ¹⁴C-activity indecapitated internodes of Phaseolus vulgaris seedlings. Differencesbetween treated and untreated tissues with respect to importof labelled assimilate were detected 3 h after application ofa mixture of IAA, GA, and SD8₃₃₉. In longer-term experimentseffects of the growth-regulator mixture on translocation oflabel were greater than those of IAA alone. Inhibitory effectsof abscisic acid on import of assimilate were counteracted bySD8₃₃₉. The ability of internode tissues to import ¹⁴C-photosynthatedeclines with time from decapitation, and a decrease in incorporationof ¹⁴C-leucine into protein was detected after 24 h. There wasan increase in protein and RNA synthesis in internodal tissuesfollowing a 2.5-h pre-treatment of decapitated internodes withIAA, GA, and SD8₃₃₉. Concentrations of 2, 3, 5-triiodobenzoicacid which inhibit ¹⁴C-IAA translocation stimulate protein synthesisin decapitated internodes, and augment the IAA-effect on importof ¹⁴C-photosynthate. ‘Hormone-directed’ assimilatetransport is discussed in relation to confounding effects ofgrowth responses and differential senescence of treated anduntreated tissues. It is suggested that accumulation of labelledassimilate in treated tissues results from effects of growthregulators on synthetic activities at the point of application.