Regulation of Leaf Shape in the Solanifolia Mutant of Tomato (Lycopersicon esculentum) by Plant Growth Substances

The solanifolia mutant (sf/sf) of tomato (Lycopersicon esculentum)produces leaves consisting of leaflets with entire margins,unlike the lobed leaflets of normal plants. Normal plants treatedwith gibberellic acid (GA₃) produced leaves with entire marginswhereas mutant plants exposed to 2-chloroethyl-trimethyl ammoniumchloride (CCC)—an inhibitor of gibberellin biosynthesis—producedlobing of leaflets. The leaf area of the mutant was significantlygreater than that of the normal, but was not significantly differentfrom GA₃-treated normal leaves. Similarly, in CCC-treated mutantleaves the leaf area was not different from that of normal untreatedleaves. These observations suggest that the sf/sf mutation affectsthe leaf shape through its effect on endogenous gibberellinsand/or inhibitory substances. Leaf shape, Lycopersicon esculentum, plant growth substances, tomato     

Inheritance of a Mutation which Suppresses Flowering in Red Clover

A spontaneous mutation isolated from stocks of red clover (cultivarS123) prevents flower initiation unless plants are suppliedexogenously with gibberellin. Mutant plants are also more uprightand densely tillering in their growth habit. Inheritance ofthe non-flowering character was analysed in a series of crossesbetween wild-type S123 and mutant plants. Hybridity followingintercrossing was confirmed using electrophoretic variants ofcytoplasmic phosphoglucose isomerase coded by a- and b-allelesof the nuclear gene Pgi-2. All F₁ plants flowered normally andwere heterozygous at the Pgi-2 locus. However, F₂ segregationsdid not provide the expected ratios, with flowering plants exceedingpredicted levels. One back-cross involving an F₁ plant and themutant parent gave flowering:non flowering and ab:aa Pgi-2 ratiosof 2:1 rather than the expected 1:1. The results are consistentwith the existence of a zygotic lethal factor, originally presentin heterozygous (non-lethal) form in the mutant (non-flowering)parent and tightly linked to the mutated gene. Segregants whichwere non-flowering always displayed the characteristic mutantgrowth form and seeds borne on these plants were lighter incolour than those borne on normal plants. Thus, there existsin red clover a gene designated ‘dig’ (developmentinfluencing gibberellin) which has several pleiotropic effectsincluding suppressing the initiation of flowering in normallyflorally-inductive environments. There are at least two allelicforms of the gene, F (flowering) and f (non-flowering).     

The role of carbohydrates in the induction of flowering in Arabidopsis thaliana: comparison between the wild type and a starchless mutant

In order to test whether an increased export of carbohydrates by leaves and starch mobilization are critical for floral transition in Arabidopsis thaliana, the Columbia ecotype as well as its starchless mutant pgm and starch-in-excess mutant sex1 were investigated. Induction of flowering was achieved by exposure of plants to either one long day (LD) or one displaced short day (DSD). The following conclusions were drawn: (i) Both the pgm and sex1 mutants have a late-flowering phenotype in days shorter than 16 h. (ii) When inductive treatments cause a large percentage of induced plants, there is always a large, early and transient increase in carbohydrate export from leaves. By contrast, when an inductive treatment results in only a low percentage of induced plants (pgm plants exposed to one DSD), the export of carbohydrates from leaves is not increased, supporting the idea that phloem carbohydrates have a critical function in floral transition. (iii) Starch mobilization is not required to obtain an increased carbohydrate export when induction is by one LD (extended period of photosynthesis), but is absolutely essential when induction is by one DSD (period of photosynthesis unaffected). (iv) Floral induction apparently increases the capability of the leaf phloem-loading system. Received: 27 August 1997 / Accepted: 6 March 1998     

Absorption and Distribution of Copper in Plants with Sufficient or Deficient Supplies

Wheat, red clover and ryegrass were grown in flowing solutionculture with sufficient (+ Cu) and deficient (–Cu) suppliesof copper. The rates of Cu absorption (µg g^–1 dryroot day^–1) did not differ greatly between species ineither treatment. Wheat plants, when transferred from the –Cu to the +Cu treatment, absorbed Cu at a much slower rate thanthose which had remained throughout in the + Cu treatment. Inall plants considerable proportions of the absorbed Cu wereretained in the roots, even when the plants were Cu-deficient,and the concentration in roots usually exceeded that in anypart of the shoots in both treatments. Transferring wheat plantsfrom the +Cu to the –Cu treatment decreased the concentrationin all plant parts except old leaves; similarly, transferringfrom the –Cu to +Cu treatment increased the concentrationin all parts of the shoots, execept old leaves, and in the roots. Lolium perenne, Trifolium pratense, Triticum aestivum, ryegrass, red clover, wheat, absorption, copper, flowing solution culture     

Gibberellin-induced Changes in Protein Synthesis and Enzyme Activity in Shoot Apices of Trifolium pratense

A mutant remaining vegetative in normally inductive long-dayconditions was used. Application of exogenous gibberellin A3(GA³) produced normal flowering under inductive long-days. Isolatedapices from treated and control plants were studied with regardto changes in size and rate of protein synthesis, as measuredby leucine incorporation. Two protein synthesis peaks were detected,one during the first 4 days after CA² application and a second,larger peak with a maximum at day 15. No consistent increasesin acid-phosphatase, aminotransferase, amylase, or peroxidasespecific activities could be associated with these peaks butan almost complete repression of alanine aminotransferase occurredduring the second protein synthesis period. The physiologicalimplications are discussed.     

Assimilate Partitioning in Red and White Clover Either Dependent on N2 Fixation in Root Nodules or Utilizing Nitrate Nitrogen

During vegetative growth in controlled environments, the patternof distribution of ¹⁴C-labelled assimilates to shoot and root,and to the meristems of the shoot, was measured in red and whiteclover plants either wholly dependent on N₂ fixation in rootnodules or receiving abundant nitrate nitrogen but lacking nodules. In experiments where single leaves on the primary shoot wereexposed to ¹⁴CO₂, nodulated plants of both clovers generallyexported more of their labelled assimilates to root (+nodules),than equivalent plants utilizing nitrate nitrogen, and thiswas offset by reduced export to branches (red clover) or stolons(white clover). The intensity of these effects varied with experiment.The export of labelled assimilate to growing leaves at the terminalmeristem of the donor shoot was not influenced by source ofnitrogen. Internode elongation in the donor shoot utilized nolabelled assimilate. Whole plants of white clover exposed to ¹⁴CO₂ on seven occasionsover 32 days exhibited the same effect on export to root (+nodules),which increased slightly in intensity with increasing plantage. Nodulated plants had larger root: shoot ratios than theirequivalents utilizing nitrate nitrogen. Trifolium repens, Trifolium pratense, red clover, white clover, nitrogen fixation, nitrate utilization, assimilate partitioning     

Flowering and gibberellins in a mutant red clover (Trifolium pratense L.)

Relationships between gibberellins and floral initiation were investigated in a conditional non-flowering mutant of red clover, Trifolium pratense. Untreated mutant plants will not flower under long-days, but will do so when certain GAs are applied. Gibberellins, A₃, A₁, A₇, and A₅ all resulted in both stem elongation and flowering whilst GA₄ produced the elongation only. Applications of GA₂₀, GA₈ and GA₁₃ under long-days had no detectable effect. Thus, by combining the use of the mutant with the application of different GAs, the correlation between the processes of stem elongation and floral initiation, which is normally strongly expressed in this species, was broken. Endogenous gibberellins shown to be present in normal plants were also found in the mutant genotype. Gibberellins alone were not sufficient to initiate floral development in the mutant, there being an essential element of interaction with long-days. These results are discussed in relation to the nature of the lesion in the mutant and the signal provided by the applied gibberellin.     

IAA-oxidase in Impatiens balsamina Affected by GA3 and Tannic Acid

The activity of IAA-oxidase increased in the leaves of Impatiensbalsamina plants receiving inductive photoperiodic cycles andin plants receiving treatments with gibberellic acid (GA₃) and/ortannic acid (TA), even under non-inductive photoperiods; theactivity also increased in the stem receiving inductive photoperiodiccycles (8 h). Treatment with GA₃ and TA mimics the effect ofSD cycles in the development of some isoenzymes of IAA-oxidase.Thus a new isoenzyme at R_f 0.48 developed in the leaves andone at R_f 0.82 developed in both the stem and the leaves ofall plants receiving inductive treatments – photoperiodicor chemical – but not in water-treated controls undernon-inductive photoperiods. Another isoenzyme at R_f 0.68 developedonly in the stems. Flowering, gibberellic acid, IAA oxidase, Impatiens, phenols, photoperiod     

Studies on the Photoreceptors for the Promotion and Inhibition of Flowering in Dark-Grown Seedlings of Pharbitis nil Choisy

Three-day-old etiolated seedlings of Pharbitis nil were exposedto red light for 10 min and sprayed with N⁶-benzyladenine beforetransfer to a 48-h inductive dark period, after which they weregrown under continuous white light. A second red irradiationpromoted flowering when given at the 5 and 24th hour of theinductive dark period but inhibited flowering at the 10 and15th hour. Far-red light inhibited flowering when given at anytime during the first 24 h of the dark period. Red/far-red reversibilitywas clearly observed at the 0, 5, 10 and 24th hour, but notat the 15th hour when both red and far-red lights completelyinhibited flowering. The action spectrum for the inhibition of flowering at the 15thhour of the inductive dark period had a sharply defined peakat 660 nm and closely resembled the absorption spectrum of theP_R form of phytochrome. The photoreceptors involved in thesephotoreactions are discussed. (Received June 10, 1983; Accepted July 6, 1983)     

Profiles of Leaf Senescence During Reproductive Growth of Sunflower and Maize

We investigated the effect of reproductive growth on the profilesof leaf senescence in maize (Zea mays L.) and sunflower (Helianthusannuus L.). Leaf senescence after flowering was assessed usingboth structural (leaf chlorophyll, nitrogen and dry matter)and functional (photosynthesis) variables in undisturbed plants(+G) and in plants in which grain set was prevented (-G). Twoweeks after flowering, lack of grain accelerated senescencein maize and delayed senescence in sunflower as indicated byleaf chlorophyll; leaf nitrogen and dry matter were less sensitiveresponse variables. Lack of interaction between reproductivetreatment and leaf position indicates that the senescence signal,whatever its nature, was equally effective throughout the plantin both species. In both species, feedback inhibition of photosynthesiswas first detected 30–35 d after flowering; excess carbohydratein the leaves was therefore an unlikely trigger of acceleratedsenescence in maize. As reproductive development progressed,differences between +G and -G plants were more marked in sunflower,and tended to disappear or reverse in maize. In sunflower, interactionsbetween leaf position and reproductive treatment—attributableto the local effect of grain—were detected around 20–27d after flowering. Copyright 2000 Annals of Botany Company Helianthus annuus, Zea mays, chlorophyll, light, nitrogen, photosynthesis, reproductive growth, senescence, source-sink, SPAD.     

The Influence of Nicotinic Acid and Plant Hormones on Flowering in Lemna

Nicotinic acid induces flowering in Lemna paucicostata 151 and381 and Lemna gibba G3 when they are grown in one tenth-strengthM medium under continuous light. For L. paucicostata 151 and381, the simultaneous addition of IAA, GA₃ or ABA to the mediumleads to an inhibition of the flower-inducing effect of nicotinicacid, while zeatin leads to a further stimulation of floweringabove that obtained by nicotinic acid alone. By contrast, inL. gibba G3 all four plant hormones inhibit the nicotinic acid-inducedstimulation of flowering. The effect of nicotinic acid on flowering in all three plantsis strongly daylength dependent when the plants are grown inhalf-strength Hutner's medium. Thus, nicotinic acid causes floweringin L. gibba G3 on continuous light but not on 9L:15D or 10L:14Dregimes. In L. paucicostata 381 nicotinic acid has a small effecton 12L:12D regime, a large effect on a 13L:11D regime and noeffect with daylengths longer than 14 hours, and in L. paucicostata151 nicotinic acid is only effective on daylengths shorter thanabout 11 hours. However, in L. paucicostata 151 and 381 treatmentwith both nicotinic acid and zeatin results in flowering undercontinuous light on half-strength Hutner's medium. Nicotinic acid is present in different Lemna but its concentrationdoes not appear to be influenced by changes in daylength. Thus,flowering clearly cannot be controlled by nicotinic acid actingalone, but the results of this study indicate that nicotinicacid could interact with other factors, possibly including oneor more of the known plant hormones, to influence the floweringprocess in Lemna. (Received August 28, 1985; Accepted October 29, 1985)     

Light Quality and Vernalization Interact in Controlling Late Flowering in Arabidopsis Ecotypes and Mutants

The late flowering ecotypes of Arabidopsis thaliana L. (Heyn.)Eifel, Pitztal and Innsbruck responded to 10 d vernalization(cold treatment) by flowering earlier with less with less thanhalf the number of leaves of non-induced plants. The vernalizationresponse was cumulative: increased numbers of days of vernalizationinduced earlier flowering up to an apparent saturation in responseafter 30 to 40 d. The ratio of red:far-red (R:FR) light alsoaffected non-vernalized time-to-flower. When grown under fluorescentplus incandescent lamps (R:FR = 1·0), time-to-flowerwas approximately half that required by plants grown under fluorescentlamps (R:FR = 5·8) at the same photon flux density andphotoperiod. Leaf production rate was unaffected by either vernalizationor light quality changes and time-to-flower and leaf numberwere highly correlated (r² = 0·973). The late flowering mutants of Landsberg erecta were grown underlighting which displayed a gradient of R:FR. Some mutants likeco, flowered at the same time in all R:FR treatment, while otherlike fca took nearly twice as long to flower, with double thenumber of leaves at R:FR ratio of 5·8 compared with theR:FR = 1 treatment. The ranking of the response from least tomost responsive was co, fe, gi, WT, fd, fwa, ft, fha, fpa, fy,fve and fca. Vernalization of these Landsberg mutants always resulted inearlier flowering, although only fca, fve, fy and fpa were significantlymore sensitive to thermoinduction than the wild type parent.There was a high correlation (r² = 0·89 between the responseto thermoinduction and to R:FR ratio. Vernalization of fca for24 d largely eliminated the R:FR time-to-flower response. Vernalizationand photoinduction similarly affect late flowering and can substitutefor each another.Copyright 1993, 1999 Academic Press Light quality, vernalization, flowering, Arabidopsis thaliana, phytochrome, thermoinduction, photoperiod, photoinduction, growth conditions, photon flux density, daylength, spectral quality, far-red light     

The Growth and Carbon Allocation Patterns of White Clover (Trifolium repens L.) Plants of Contrasting Branching Structure

The growth, morphology and carbon allocation patterns of F1progeny white clover (Trifolium repens L.) plants selected foreither low (‘LBF’) or high (‘HBF’) frequencyof stolon branching were compared in two controlled-environmentexperiments. Selections from within both a small-leaved (‘GrasslandsTahora’) and a large-leaved (‘Grasslands Kopu’)clover cultivar were compared, and plants were grown under arelatively lenient defoliation treatment (expt 1) or under threelevels of defoliation seventy (expt 2). Carbon allocation patternswere measured by ¹⁴CO₂ pulse-chase labelling using fully unfoldedleaves on the main (parent) stolon. LBF and HBF displayed consistent differences in the selectedcharacter though, within cultivars, the difference between selectionswas most pronounced for Kopu. The selections developed fundamentallydifferent branching structures resulting from differences inbranching frequency, with total branch weight per plant averaging122 mg for LBF and 399 mg for HBF (mean of both experiments).More C moved from parent stolon leaves to branches in HBF thanin LBF (mean 22.6% vs. 15.1% respectively of the ¹⁴C exportedfrom source leaves). More C also moved to stolon tissue in HBF,but, counterbalancing this and the difference in allocationto branches, less moved to developing leaves and roots on theparent stolon itself compared to LBF. However, the total weightof developing leaves and roots per parent stolon was generallygreater in HBF than in LBF, probably reflecting greater C importby these sinks from the higher number of branches present perplant in the former selection. HBF plants were consistentlylarger at harvest than LBF plants. There were no defoliationtreatment x selection interactions in C allocation patternsin expt 2. The implications of the results for plant performancein grazed pastures are discussed. Branching, carbon translocation, defoliation, growth, morphology, Trifolium repens, white clover     

The Negative Response of Photoperiodic Floral Induction in Chenopodium rubrum L. to Preceding Growth

In Chenopodium rubrum there exists a correlation between theage of the seedlings and the effectiveness of photoperiodicinduction. The younger the plants the more effective was photoperiodictreatment. In three-day-old seedlings one short day was sufficientto promote incomplete flowering, while two short days broughtabout 100 per cent flowering. With six-, eight-, and ten-day-oldplants exposed to two or three short days quantitative differenceswere observed in the earliness of flowering and the percentageof flowering plants. The effects of continuous light and ofshort days with a light break preceding the inductive treatmentwere compared. The results obtained indicate that the inhibitoryeffect of plant age cannot be attributed solely to the appearanceof inhibitors under continuous light but changes of growth patternin plants of different age should also be taken into consideration. The inhibition of RNA synthesis in shoot apices brought aboutby 6-azauridine resulted also in a flowering stimulation, providedthat the inhibitor was applied one or two days prior to inductionand the inductive process itself remained undisturbed. Thisstimulation was accompanied by inhibition of vegetative growthand by a decrease of RNA concentration in the cytoplasm as estimatedcytophotometrically. The competition between growth of vegetative organs and floraldifferentiation affects the response to inductive treatment.The suppression of growth can result in enhancement of flowering.     

Rm Differences in Leaf Malate Dehydrogenases of Flax (Linum usitatissimum) Genotrophs: Apparent Developmental Effects

Fieldes, M. A. and Gray, T. J. 1988. R_m differences in leafmalate dehydrogenases of flax (linum usitatissimum) genotrophs:apparent developmental effects.—J. exp. Bot. 39: 499–509. Malate dehydrogenase (MDH) isozyme relative mobility (R_m) wasexamined in leaf extracts of Durrant's large (L) and small (S)flax genotrophs. Within both L and S there were differencesin R_m between leaves sampled from different positions down themain stem and between leaves sampled from plants of differentages. For leaves sampled from plants which were at the onsetof flowering, the R_m differences from the apex to the base ofthe stem showed similar trends in L and S. However, the neteffect of the trend for L was a linear increase in R_m from apexto base, which did not occur in S. The changes in R_m which occurredin apical leaves as the plants aged were also different in Land S; R_mdecreased in L and increased in S during the growthperiod just prior to flowering. The possible relationship betweenthese differences in the changes in MDH R_m within L and S, previouslyreported differences in the changes in peroxidase (PER) isozymeR_m and the morphological/developmental differences between Land S is discussed. In addition, the experimentation demonstratedthat ‘negative’ bands detected in MDH-stained gelsunder certain staining conditions appear to correspond to PERisozymes and effectively mean that PER and MDH isozyme R_m'scan be obtained from the same electrophoretic gels. Key words: Malate dehydrogenase, peroxidase, relative mobility, flax     

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     

Characterization of an Arabidopsis thaliana Mutant that Has a Defect in ABA Accumulation: ABA-Dependent and ABA-Independent Accumulation of Free Amino Acids during Dehydration

In an attempt to elucidate the physiological role of ABA inseed dormancy and the adaptive response to dehydration, we isolatedan ABA-deficient mutant of Arabidopsis thaliana (L.) Heynh.which germinated in the presence of a gibberellin biosyntheticinhibitor. Genetic analysis showed this mutation is a new alleleof a recently reported locus aba2, and therefore has been designatedaba2-2. The levels of endogenous ABA in fresh and dehydratedtissues of the aba2-2 mutant were highly reduced compared tothose of wild-type plants. As a consequence, aba2-2 plants wiltand produce seeds with reduced dormancy. Dark germinated seedlingsof the aba2-2 mutant showed true leaves, which were not observedin those of the wild type, indicating that abal-2 em bryos grewprecociously during seed maturation. In the dehydrated tissuesof the wild-type plants, the levels of free proline, isoleucineand leucine were elevated to a content approximately 100-foldhigher than those in fresh tissues. In contrast to the wild-typeplants, dehydration-induced accumulation of proline was highlysuppressed in the aba2-2 mutant plants while that of leucineand isoleucine accumulated. Furthermore, exogenous applicationof ABA to wild-type plants promoted accumulation of free proline,but not leucine nor isoleucine. These results suggest that dehydration-inducedaccumulation of free leucine and isoleucine is achieved independentof ABA. (Received March 5, 1998; Accepted June 2, 1998)     

Studies on the Role of Photosynthesis in the Photoperiodic Induction of Flowering in the Short-Day Plants Kalanchoe blossfeldiana Poellniz and Xanthium pensylvanicum Wallr: I. THE REQUIREMENT FOR CO2 DURING PHOTOPERIODIC INDUCTION

It has been established that Kalanchoe blossfeldiana and Xanthiumpensylvanicum require CO₂ during the light period of short daysfor successful photoperiodic induction of flowering, even ifall but the induced leaf are held in normal air. In X. pensylvanicumfloral induction in normal air was independent of the starchstatus of the leaves but when reserves were reduced, lack ofCO₂ in the light suppressed floral induction to an even greaterextent. Injection into the induced leaf (Kalanchoe) or leaftip feeding (Xanthium) of carbohydrates, organic and amino acidsor several other metabolites failed to substitute for the CO₂requirement for induction. A small response was produced by10 mg ml^–1 sucrose in X. pensylvanicum while in normalair 25 parts 10^–6 ATP reduced the time to flowering inK. blossfeldiana and 10^–4 M proline was inhibitory. Anexperiment on the light requirement established a need for redlight ( max 660 nm) during photoperiods but red light alonedid not facilitate maximal induction. It is concluded that someearly, possibly labile, product of photosynthetic CO₂ fixationis essential to floral induction in these species.     

Studies with Liatris spicata Willd. 1. Effect of Temperature on Sprouting, Flowering and Gibberellin Content

Dormancy was induced during storage of Liatris spicata cormsgrown in Israeli summer conditions, but plants left in soilcontinued vegetative growth. Corms of winter-grown plants sproutedfreely. Treatment with GA₃ restored both sprouting and floweringin summer-grown corms, but in winter corms GA₂ was effectiveonly after corms were stored at low temperature. All the plantsflowered after 4 weeks at 2 °C and GA³ treatment. The content of gibberellins in the main bud of freshly excavatedcorms decreased during the first 18 d of storage but increasedto the initial level after 4 months of cold storage. The numberof flowering stems increased to 2.5 per corm when corms werecold-stored up to 75 d, but decreased with a longer storage. Liatris spicata, dormancy, flowering, gibberellin, sprouting     

Flower-Inducing Activity of Exogenous Lysine in Lemna paucicostata 151 Cultured on Nitrogen-Rich Medium

Flower-inducing activity of lysine was examined in Lemna paucicostata151, a weakly responsive short-day plant, cultured on nitrogen-richmedium under long-day conditions (continuous light). Lemna paucicostata151 was homogenized in a solution of lysine and the homogenatewas centrifuged. The supernatant (lysine-containing extract)was added to nitrogen-rich medium after passage through a membranefilter to give various concentrations of lysine in the medium.Flowering was induced in plants grown for six days on mediumthat contained lysine at concentrations above 0.25 µM.In plants grown on medium that contained 1 µM lysine,a significant flowering response was observed on the fourthday of culture. However, the flower-inducing activity of lysinedisappeared when the lysine-containing extract was added tothe medium and the medium was then autoclaved, suggesting thatthe active principle is unstable to autoclaving. Among derivativesof lysine tested, lysine hydroxamate had the highest flower-inducingactivity and lysyl lysine had almost same activity as that oflysine. When added to the medium without homogenization withplant material, lysine and lysyl lysine had flower-inducingactivity but lysine hydroxamate did not induce flowering. (Received April 26, 1993; Accepted November 8, 1993)