Correlation between Long-Day Flowering and Root Elongation in Pharbitis nil, Sfrain Kidachi

Long-day flowering of Pharbitis nil, dwarf strain Kidachi, at20?C was greatly influenced by the size of the culture vesseland the number of plants per vessel. The smaller the vessel,the greater the flowering response. The volume of nutrient solutionper plant was not decisive for long-day flowering. For instance,plants cultured singly in 200-ml beakers flowered, but thosecultured in 5,000-ml vessels (33?26?11.5 cm, 48 plants per vessel)did not, even though there was only about 100 ml of nutrientsolution per plant. Long-day flowering was always accompaniedby the suppression of root elongation, but not by a decreasein the dry weight of roots or shoots, or in the rate at whichthe leaf primordia appeared (plastochrone). Aeration of thenutrient solution or culture in vermiculite promoted root elongationeven in small vessels, thereby inhibiting long-day flowering.Thus the suppression of root elongation seems to be necessaryfor long-day flowering. Removal of the roots or cotyledons;however, suppressed long-day flowering even when root elongationwas inhibited by culture in small vessels. When plants werecultured at 24?C, suppression of root elongation (culture ina small vessel) did not induce long-day flowering; but, short-daytreatment induced flowering without suppressing root elongation. (Received April 19, 1982; Accepted June 24, 1982)     

Effect of nitrate concentration in the medium on the flowering of Lemna paucicostata 6746

Addition of copper or tungstate to or exclusion of molybdenumfrom M-sucrose medium induced long-day flowering in Lemna paucicostata6746 provided the medium contained sufficient nitrate. By contrast,ferricyanide, cyanide or silver induced long day flowering evenin nitrate-deficient, M-sucrose medium. (Received August 26, 1977; )     

Absorption of Copper by Lemna as Influenced by Some Factors Which Nullify the Copper Effect on Flowering and Growth

The effect of copper on flowering and growth of Lemna paucicostata6746 and Lemna gibba G3 in a copper-containing medium is nullifiedby the addition of EDTA, ammonium ions or salicylic acid tothe medium or a decrease in its nitrate concentration. Thesefactors were examined for their effects on the absorption ofcopper by the plants. The addition of EDTA to the medium completelyinhibited the absorption of copper in both species, thus eliminatingthe copper effect. Ammonium ions also inhibited copper absorption,their effectiveness rising with their concentration. Loweringthe nitrate concentration in the medium nullified the coppereffect on flowering in L. paucicostata 6746, and the additionof salicylic acid to the medium also nullified the copper effectin L. gibba G3, both without affecting the absorption of copper. (Received June 7, 1982; Accepted August 27, 1982)     

Effect of High-intensity Light Given Prior to Low-temperature Treatment on the Long-day Flowering of Pharbitis nil

Pharbitis nil, strain Violet which had been exposed to high-intensitylight (18,000 lux at 23?C) for 7 days followed by a low-temperaturetreatment (13–14?C) for 7 days initiated flower buds evenunder continuous light, but plants given these treatments inreverse order failed to bud. Three days of high-intensity lightat 23?C was most effective in promoting the flower-inducingeffect of the subsequent low-temperature period. Six days oflow temperature following the 3-day high-intensity light periodinduced near-maximum flowering response. DCMU (5?10^–6M) given during the high-intensity light period inhibited flowering,but when given during or after the low-temperature period itwas ineffective. DCMU at the same concentration given before,during or after an inductive 16-hr dark period at 26?C did notinhibit flowering. Sucrose, ATP, NADPH and some other reducingagents tested did not nullify the DCMU effect nor substitutefor the effect of high-intensity light. But, the high-intensitylight effect could be substituted, at least partly, by 5-chlorosalicylicacid, 3,4-dichlorobenzoic acid and some other benzoic acid derivatives,which are highly effective in inducing long-day flowering inthe short-day plant, Lemna paucicostata. (Received October 20, 1981; Accepted February 3, 1982)     

Influence of Zeatin on Flowering in Root Forming Cuttings of Anagallis arvensis L.

Applied zeatin affected flowering in cuttings of Anagallis arvensis(long-day plant). According to the zeatin concentration andthe root formation stage, zeatin inhibited flowering at differentdegrees or slightly promoted it. Thus, the root primordium settingseemed to be correlated with this effect of zeatin. (Received February 14, 1984; Accepted May 18, 1984)     

Long-day Induced Dormancy in Anemone coronaria L

In Anemone coronaria L. summer dormancy in Israel can be inducedby long photoperiods even in the middle of the winter. Cultivationin Europe has reduced but not eliminated this response to daylength.Daylength did not affect the time of flowering but dormancycaused early cessation of flowering under long days. Anothereffect of long-day treatment was to produce longer scapes. Anemone coronaria, summer dormancy, long-day induction, daylength response     

Effects of some metabolic inhibitors on flowering of Lemna gibba G3, a long-day duckweed

Flowering of Lemna gibba G₃, a long-day duckweed, was inhibitedby adding CuSO₄, AgNO₃, HgCl₂, Na₂WO₄ or iodoacetamide to themedium at the concentrations inducing long-day flowering inLemna paucicostata 6746, a short-day duckweed. This suggeststhat these metabolic inhibitors affected the photoperiodic sensitivityrather than directly affecting flower initiation. Ferricyanidepromoted flowering in both of these short-day and long-day duckweeds. (Received July 7, 1977; )     

Flowering Induced by Nitrogen Deficiency in Lemna paucicostata 151

Lemna paucicostata 151 is a weakly responsive short-day plantwhen grown in non-aseptic ten-fold diluted E medium supplementedwith 1 µM 6-benzyladenine, but it flowered even underlong-day conditions (continuous light) when grown in this mediumfor more than 14 days. On the 14th day of culture, the levelof endogenous nitrogen in the plants decreased to about 60%of that in the plants inoculated at the start of the culture.The flowering obtained under long-day conditions was suppressedby raising the concentration of nitrogen in the medium, whileit was induced more rapidly by lowering the concentration ofnitrogen in the medium. Benzyladenine did not cause floweringby itself, but it was required for the flowering that was inducedby a reduction in the level of nitrogen in the medium. Thus,the flowering observed under long-day conditions is due to nitrogendeficiency in the plants. Two inhibitors of proteases, bestatin and elastatinal, clearlyinhibited the flowering induced by nitrogen deficiency. It appears,therefore, that the induction or activation of some protease(s)is involved in the flowering that is induced by nitrogen deficiency. (Received March 19, 1991; Accepted August 16, 1991)     

Enhancement of long-day flowering by Mo-deficiency and application of some amino acids and asparagine in the short-day plant Lemna paucicostata 6746

The short-day plant Lemna paucicostata 6746 can be induced toflower on long days (continuous light) by the addition of copper,tungstate or ferricyanide to the medium, and in each case theeffect was greatly enhanced by deleting molybdate from the medium.Treatment with asparagine, aspartate, glutamate, -alanine, glycineorserine, all of which are known to increase the critical daylengthand almost nullify the light-break effect in L. paucicostata6746, enhanced the long-day flowering induced by copper, ferricyanideor Mo-deficiency. (Received October 13, 1978; )     

Suppression of long-day flowering by nitrogenous compounds in Lemna perpusilla 6746

The long-day flowering of Lemna perpusilla 6746 on an SH inhibitor-containingmedium was inhibited by the application of ammonium ion to themedium. Ammonium ion not only suppressed long-day flowering,but relieved the inhibition of vegetative growth caused by theinhibitors. Nitrite, casamino acids, glutamine and asparaginehad a similar effect, suggesting that the inhibition of long-dayflowering by ammonium ion is not a direct effect of the ion.Most amino acids, with the exception of glutamate and aspartate,also prevented long-day flowering, but their effects on vegetativegrowth varied. No qualitative differences in amino acid compositionwere observed among plants cultured on media containing nitrate,nitrite or NH4₄NO₃as the sole nitrogen source. However, theamounts of free and total amino acids werehigher in plants fedwith nitrite or NH₄NO₃ than in those fed with nitrate. Thissuggests that the inhibition of long-day flowering by ammoniumand nitrite can be ascribed to increased nitrogen metabolism. Though decreased activity by SH inhibitors of nitrate reductase(SH enzyme) is assumed to result in long-day flowering by loweringthe nitrogen metabolism, lowering the nitrogen level in M mediumdid not bring about floral initiation in the absence of SH inhibitors. (Received January 7, 1975; )     

Flower-Inducing Activity of Phloem Exudate in Cultured Apices from Pharbitis Seedlings

Phloem exudate from cotyledons of photoperiodically inducedPharbitis plants induced flowering in apices excised from non-inducedseedlings and cultured in vitro. The exudate also stimulatedflowering in apices excised from photo-induced seedlings andcultured under long-day conditions. The application of benzoicacid had similar effects. Both the exudate from non-inducedplants and gallic acid suppressed flowering in apices from photo-inducedseedlings. It appears that the phloem exudate contains flower-inducingor flower-suppressing substance(s), depending on the plant materialsfrom which it was collected. (Received August 15, 1989; Accepted May 14, 1990)     

Effect of Ferricyanide, Ferrocyanide and KCN on Growth and Flowering in the Short-Day Plant Lemna paucicostata 6746

Flowering in the short-day plant Lemna paucicostata 6746 canbe induced under continuous light by the addition of ferricyanie,ferrocyanide or KCN to M-sucrose medium. Each substance is nearly10 times more effective when the flasks are covered by glassbeakers than when cotton plugs are used. By contrast, when floweringis induced under continuous light by copper or by short-daytreatment, neither flowering nor growth are affected by whetherglass beakers or cotton plugs are used. Ferricyanide, ferrocyanideand KCN are also able to induce long-day flowering when theplants are grown on Msucrose medium in small beakers that areplaced in a covered storage dish that also contains a solutionof one of these compounds. Addition of a KOH trap to the storagedish completely blocks the flowering induced by these compounds.If [¹⁴C]ferrocyanide is added to the storage dish both the M-sucrosemedium and the plants contain significant amounts of radioactivity,the amount of radioactivity being proportional to the floweringresponse. These results indicate that ferricyanide, ferrocyanideand KCN break down to release HCN and that it is the HCN whichis responsible for inducing flowering in L. paucicostata 6746under continuous light. ¹Present address: Department of Biology, Osaka Kyoiku University,Ikeda, Osaka 563, Japan. ²Present address: Institute of Horticulture, The Volcani Center,P. O. B. 6, Bet-Dagan, Israel. (Received January 17, 1983; Accepted March 24, 1983)     

Growth and development in Phalaris III. Effect of temperature on critical daylength in geographic strains of P. tuberosa L.

The critical daylength for flowering in Phalaris tuberosa L.,a cold-requiring, long-day plant, increases with increasingtemperature. The significance of this phenomenon is discussedin relation to the control of flowering time and the photoperiodicresponse mechanism. (Received November 5, 1968; )     

Reproductive Development and Nitrogen Fixation in Soybean (Glycine max [L.] Merril)

Gomes, M. A. F. and Sodek, L. 1987. Reproductive developmentand nitrogen fixation in soybean (Glycine max (L.) Merril).—J.exp. Bot. 38: 1982–1987. Nitrogenase activity (acetylene reduction) was measured duringthe growth cycle of soybean plants induced to flower at twodifferent ages. The decline in nitrogenase activity towardsthe end of the cycle was clearly associated with pod-fillingfor both flowering dates when plants were cultivated under lowerlight and temperature conditions (out of season). Under higherlight and temperature conditions (normal growing season) thedecline was independent of the flowering date. Furthermore,the timing of the decline was not altered when plants were maintainedunder long-day (vegetative) conditions nor when flowers wereremoved. It is suggested that under more favourable growth conditionsthe diversion of assimilates by the fruits is not the primarycause of the decline in nodule activity, but competition bythe fruits may be important when the production of photo-assimilatesis more limited. Key words: Glycine max, nitrogenase, source-sink     

Flowering of S. 24 Perennial Ryegrass (Lolium perenne L.) in Short Days at Low Temperature

The flowering of the quantitative long-day plant perennial ryegrass(Lolium perenne L.) in short days (8 h), when grown at low temperature(9/4 °C) and under natural summer daylight, is presentedas evidence for the replacement of specific environmental requirementsfor flowering by alternative stimuli in a grass.     

Formation of Chlorophyll-Protein Complexes in Greening Cucumber Cotyledons in Light and then in Darkness

The changes in chlorophyll-protein complexes (CPs) in cucumbercotyledons during illumination and subsequent dark incubationwere studied by SDS-polyacrylamide gel electrophoresis. Whenetiolated cucumber seedlings were illuminated, chlorophyll wassynthesized and CPs were formed. In the early phase of greening(6 h of illumination), light-harvesting chlorophyll a/b-proteincomplex (LHCP) was the main GP. As the greening proceeded, P700chlorophyll a-protein complex (CP1) accumulated. When 6-h illuminatedseedlings were transferred to darkness, CP1 accumulated concomitantlywith a decrease in LHCP without new chlorophyll synthesis. Thechanges in the amounts of CPs in the dark became smaller withthe progress of greening and were not observed after 72 h ofillumination. These changes were confirmed by examining thechlorophyll/P700 ratio and the low temperature absorption spectrumof cotyledons. These results suggest that in the early phaseof greening, CPs were unstable and their chlorophyll moleculeseasily exchanged with those of other kinds of CPs. (Received October 14, 1982; Accepted December 1, 1982)     

Inhibition of flowering in the long-day plant Lemna gibba G3 by Hutner's medium and its reversal by salicylic acid

Flowering in the long-day plant Lemna gibba L., strain G3 ispoor or absent in Hutner's medium even under continuous light,an effect generally ascribed to the ammonium content of themedium. However, flowering is also inhibited in ammonium-freemodifications of Hutner's medium, particularly in the presenceof sucrose, but is restored to high levels by the presence of10 µu salicylic acid. These results link two of the leastunderstood chemical effects in Lemnaceae flowering, and theyprovide a system in which large effects of salicylic acid canbe readily obtained. ²Present address: Lab. of Applied Bot., Fac. of Agric, KyotoUniv., Kyoto 606, Japan. (Received January 27, 1979; )     

Inhibition of Flowering in the Long-Day Plant Lemna gibba G3 by Hutner's Medium and its Reversal by Medium Modification

The long-day plant Lemna gibba G3 flowers normally in E medium(Hoagland-type medium plus 30 µM EDTA) but in 0.5 H mediumthere is no flowering. Ammonium is present in 0.5 H medium andis known to inhibit flowering in L. gibba G3, but even in NH₄⁺-free0.5 H medium there is virtually no flowering under continuouslight. Increasing the phosphate concentration of the NH₄⁺-free0.5 H medium from 1.15 ITIM to 12 or 16 mM results in substantialflowering. Decreasing the EDTA concentration from 850 µIMto 250 µM, or raising the nitrate concentration from 4mM to 12 mM, results in only a small increase in flowering.If the decrease in EDTA and increase in nitrate are combinedwith the increase in phosphate, however, the flowering responseis nearly as good as that obtained using E medium. Thus, withthese three changes the inhibitory effect of NH₄⁺free 0.5 Hmedium for flowering in L. gibba G3 is almost completely reversed In the above studies flowering was not limited by daylength.When plants were grown on E medium under an 11 hour daylengthwhere flowering is limited by daylength, decreasing the phosphateconcentration in the medium reduced flowering, but increasingthe phosphate concentration in the medium did not stimulateflowering. Thus, when flowering is limited by daylength, highphosphate will not cause flowering, but a certain level of phosphateappears to be necessary for the expression of photoinductionunder long days. (Received January 14, 1986; Accepted June 24, 1986)     

Flowering of the long-day plant, Lemna gibba, under short-day schedules composed of red and far-red light

Flowering in Lemna gibba, a long-day duckweed, can be inducedunder a short-day condition when the photoperiodic regimes areR₇FR₃ (7 hr red followed by 3 hr far-red), R₅FR₅ and R₃FR₇.This indicates the necessity of a proper balance between redand far-red effects for flowering. The flowering induced bythese regimes is inhibited by a brief exposure to red givenat the start of darkness and this inhibition is reversed bysubsequent exposure to far-red. Thus, the red/far-red reversibleeffect is found only at the beginning of darkness for floweringof L. gibba. However, flowering of L. gibba is promoted by a red light breakgiven near the middle of a 14 hr dark period. The promotiveeffect is not reversed by subsequent exposure to far-red, i.e.,the effect of the red break converts from inhibition to promotionas when given later in the dark period, which suggests the involvementof a timing mechanism. (Received July 21, 1973; )     

Darkness promotes flowering in the absolute long-day requiring plant, Lolium temulentum L. Ceres

Vegetative plants of the long-day grass Lolium temulentum L.Ceres were exposed to threshold long days or light breaks. Protracteddarkness given just afterwards clearly promoted flowering andwas weakly inductive on its own. The promotive effect of darknesswas restricted to floral induction since further apical developmentwas weak. Key words: Lolium temulentum, flowering, photoperiodism, darkness