Patterns of Assimilate Distribution and Source--sink Relationships in the Young Reproductive Tomato Plant (Lycopersicon esculentum Mill.)

Patterns of distribution of ¹⁴C were determined in 47-day-oldtomato plants (Lycopersicon esculentum Mill.) 24 h after theapplication of [¹⁴C]sucrose to individual source leaves fromleaves 1–10 (leaf 1 being the first leaf produced abovethe cotyledons). The first inflorescence of these plants wasbetween the ‘buds visible’ and the ‘firstanthesis’ stages of development. The predominant sink organs in these plants were the root system,the stem, the developing first inflorescence and the shoot ‘apex’(all tissues above node 10). The contribution made by individualsource leaves to the assimilate reaching these organs dependedupon the vertical position of the leaf on the main-stem axisand upon its position with respect to the phyllotactic arrangementof the leaves about this axis. The root system received assimilateprincipally from leaf 5 and higher leaves, and the stem apexfrom the four lowest leaves. The developing first inflorescencereceived assimilates mainly from leaves in the two orthostichiesadjacent to the radial position of the inflorescence on thevertical axis of the plant; these included leaves which weremajor contributors of ¹⁴C to the root system (leaves 6 and 8)and to the shoot apex (leaves 1 and 3). This pattern of distributionof assimilate may explain why root-restriction treatments andremoval of young leaves at the shoot apex can reduce the extentof flower bud abortion in the first inflorescence under conditionsof reduced photoassimilate availability. Lycopersicon esculentum Mill, tomato, assimilate distribution, source-sink relationships     

Changes in Dry Matter, Carbohydrate and Seed Yield Resulting from Lodging in Three Temperate Grass Species

The adverse effect of lodging on grass seed yield may be attributed,in part, to assimilate limitation during the seed filling period.This investigation examined plant dry matter assimilate partitioningand seed yield as affected by lodging in three species thatare closely related but phenotypically different: tall fescue(Festuca arundinacea Schreber.), Italian ryegrass (Lolium multiflorumLam.), and perennial ryegrass (L. perenne L.). Studies wereperformed in field plots at Corvallis, Oregon, USA. Seed yieldcomponents (seed number per inflorescence, seed yield per inflorescence,and single seed mass) and leaf, stem (lower, middle, and peduncle)and seed inflorescence dry mass were measured just prior toanthesis to seed maturity. Dry mass and water soluble carbohydrates(WSC) were determined for shoot components. The reduction indry mass and WSC in leaves and stem components following anthesiswas often greater in lodged plants compared to upright plants.The relatively low seed yield depression in lodged tall fescuesuggested a higher compensation potential for partitioning reserveassimilate from leaves and stems to support seed growth anddevelopment. This potential does not appear to be present tothe same degree in Italian ryegrass and to an even lesser extentin perennial ryegrass. These findings suggest that the potentialto compensate for reduced assimilate supply during the periodof high assimilate demand by seeds may be attributed, in part,to the total assimilate reserve accumulated prior to photoassimilatereduction caused by the lodged condition. Copyright 2000 Annalsof Botany Company Tall fescue, Festuca arundinacea Schreber., Italian ryegrass, Lolium multiflorum Lam., perennial ryegrass, L. perenne L., assimilate partitioning, source–sink     

The Presence of Photosynthetic Machinery in Aerial Roots of Leafy Orchids

Three photosynthetic enzymes were characterised in extractsfrom leaves and aerial roots of Aranda ‘Christine 130’.The enzymes from both tissues were similar in activity and kineticproperties. Grana-containing chloroplasts were found in rootcells of Vanda suauis. Thus components crucial to photosynthesisare present in aerial roots of these leafy orchids. (Received March 22, 1983; Accepted July 7, 1983)     

The Effect of Photon Flux Density and Duration of the Photosynthetic Period on Growth and Dry Matter Distribution in Carrot

The distribution of dry matter between shoot and storage rootof carrot plants grown in light regimes varying in intensity,duration and integral, is used to test an hypothesis for thecontrol of assimilate partition Results from seven varietiesshow that shoot to storage root weight ratios are affected bythe light environment, but that these effects are associatedwith the effect of light on plant size It is concluded thatquantitative alterations to the supply of assimilate, resultingfrom variation in the light regime, do not affect its partitionto different organs This is discussed in relation to other investigationswhich have suggested a relationship between the duration ofthe photosynthetic period, assimilate sequestration in foliarstarch and partition between shoot and root Daucus carota L, carrot, assimilate partition, light intensity, daylength, shoot, storage root, shoot-root ratio, source-sink relations     

Patterns of 14C-labelled Assimilate Partitioning in Red and White Clover During Vegetative Growth

A quantitative analysis of the ¹⁴C-labelled assimilate suppliedby the expanded leaves on the primary shoot to growing leaves,stem, lateral shoots (branches or stolons) and roots in redand white clover was conducted during vegetative growth. Stem growth of the primary shoot was inhibited in both cloversand utilized no energy resources. The growing leaves at theprimary shoot apex of white clover imported 4 per cent of theshoot's assimilate compared with 10 per cent in red clover.At the basal end of the primary shoot, the tap root of whiteclover imported 16 per cent of the shoot's assimilate comparedwith 22 per cent in red clover. Branches in red clover and stolonsin white clover were by far the largest sinks for primary shootassimilate, importing 39 per cent and 63 per cent of the labelledassimilate, respectively. Analyses of the translocation of assimilate from individualprimary shoot leaves demonstrated that in both clovers olderleaves exported more of their assimilate to branches or stolons,whereas younger leaves exported more of their assimilate toroots, and possibly in white clover, to growing leaves at thetip of the shoot. Of the labelled assimilate exported to branchesor stolons, each primary shoot leaf exported preferentiallyto the branch or stolon in its own axil, but in addition exportedsubstantial quantities of assimilate to all other axillary shoots,particularly those arising from basal axils where the subtendingleaf had died. Trifolium repens, Trifolium pratense, red clover, white clover, assimilate partitioning, perennation     

Spike initiation in Plantago ovata Forssk.

Histological studies on Plantago ovata indicated that spikeinitiation occurs from neither the shoot apex nor the axilsof young leaves. The first detectable inflorescence primordium,noticed in the axils of older leaves, gives rise to spike primordiumat later stages of development. Plantago ovata Forssk., inflorescence initiation, shoot apex     

Effect of Assimilate Supply on Development and Growth Potential of Axillary Buds in Roses

The effect of assimilate supply on axillary bud developmentand subsequent shoot growth was investigated in roses. Differencesin assimilate supply were imposed by differential defoliation.Fresh and dry mass of axillary buds increased with increasedassimilate supply. The growth potential of buds was studiedeither by pruning the parent shoot above the bud, by graftingthe bud or by culturing the bud in vitro. Time until bud breakwas not clearly affected by assimilate supply during bud development,Increase in assimilate supply slightly increased the numberof leaves and leaf primordia in the bud; the number of leavespreceding the flower on the shoot grown from the axillary budsubstantially increased. No difference was found in the numberof leaves preceding the flower on shoots grown from buds attachedto the parent shoot and those from buds grafted on a cutting,indicating that at the moment of release from inhibition thebud meristem became determined to produce a specific numberof leaves and to develop into a flower. Assimilate supply duringaxillary bud development increased the number of pith cells,but the final size of the pith in the subsequent shoot was largelydetermined by cell enlargement, which was dependent on assimilatesupply during shoot growth. Shoot growth after release frominhibition was affected by assimilate supply during axillarybud development only when buds sprouted attached to the parentshoot, indicating that shoot growth is, to a major extent, dependenton the assimilate supply available while growth is taking place.Copyright1994, 1999 Academic Press Assimilate supply, axillary bud, cell number, cell size, defoliation, development, growth potential, meristem programming, pith, Rosa hybrida, rose, shoot growth     

Influences of Certain Plant Factors on the Growth and Fruiting of the Lower Axillary Shoot of Lycopersicon esculentum Mill

Excision of the first inflorescence at diffrent stages of development,emasculation of the anthers before anthesis, and excision of of the entire root system at transplanting significantly enhahcedthe growth and fruiting of the axillary shoot located directlybelow the first inflorescence of Lycopersicon esculentum Mill.cv. Fireball. Replacement of the inflorescence with a combinationof indol-3yl-acetic acid, gibberellin A_4/7 and N⁶-benyladenineat 5 x 10^–4 M concentration in lanolin delayed the timefor the axillary shoot to attain a length of 20 cm. Enchancementof growth and fruiting of the auxillary shoot below the firstinflorenscence was attributed to a greater availability of assimilate.     

Regulation of Floral Initiation and Development in an Orchid Hybrid Aranda Deborah

The effects of growth regulators on floral initiation and developmentin a monopodial orchid hybrid. Aranda deborah, were studied.Auxin, gibberellic acid and abscisic acid did not stimulateany floral initiation. Auxin antagonists and growth retardantsstimulated floral initiation but many of the initiated budsdid not continue to develop to maturity. Cytokinin (6-benzylaminopurine)stimulated not only bud initiation but also floral developmentto maturity. A distinction was made between the process of floral initiationand floral development. It was suggested that both these processeswere regulated by the correlative apical dominance effect.     

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     

Sex expression as affected by N6-benzylaminopurine in staminate inflorescence of Luffa cylindrica

The effect of N⁶-benzylaminopurine (BA) on the sex expressionof staminate inflorescences of Luffa cylindrica was investigated.Direct application of BA to the staminate inflorescence inducedbisexual and pistillate flowers and finally caused the inflorescenceto develop into a shoot that was similar to the main shoot.Such modification in a staminate inflorescence from the proximalto the distal nodes is usually in the order of staminate flowers,bisexual flowers, pistillate flowers and foliage leaves (shoot).Pinching of the main stem also caused the inflorescence to developinto a shoot in the absence of lateral shoots. BA-induced femalenesswas strengthened when the number of leaves remaining on theplant was increased. On the other hand, application of BA tothe shoot apex of the main stem starting at the 2-leaf stagesuppressed differentiation of the flower bud on the main stem. (Received December 22, 1979; )     

The Translocation of 14C-Labelled Assimilates in Dwarf Bean Plants Infected with Xanthomonas phaseoli (E.F.Sm.) Dowson

The distribution of ¹⁴C-labelled assimilates in dwarf beansinfected on one unifoliate with Xanthomonas phaseoli or systemicallyinfected with the pathogen was compared with the distributionin plants subjected to water stress. Unifoliates on systemically-infectedand water-stressed plants retained a much greater proportionof assimilated ¹⁴CO₂ than equivalent leaves on healthy plants,but unifoliates directly inoculated with X. phaseoli (localinfection) retained only a slightly larger proportion than controlplants. Local infection had little influence on the distribution ofexported radiocarbon but systemic infection produced markedeffects and there were similar changes in water-stressed plants.These changes seem to be related mainly to changes in growthpatterns, particularly to the reduced development of trifoliateleaves. The main causes of the altered assimilate distributionappear to be modified source-sink relationships, but the natureof the vascular system of dwarf bean and interference with vascularfunction by X. phaseoli seem to be more significant factorsthan in other diseases where assimilate distribution has beenstudied.     

A Space-time Model of Carbon Translocation along a Shoot Bearing Fruits

A carbon-based model is described of the source-sink relationshipsof a stem bearing fruits in space and time and focusing on growthvariability along the branch. The novelty of the model comesfrom the aggregation of physiological processes taking intoaccount spatial aspects. The stem is represented as a set ofcompartments (metamers) connected to source (leafy shoots) andsink (fruits) compartments. Each leafy shoot forms one compartment.The fruit consists of three compartments involved in translocation(cytoplasm), structure (cell wall) and storage (vacuole). Physiologicalprocesses considered are photosynthesis, respiration of fruitsand leaves, translocation of assimilates and fruit growth. Assimilateproduction is regulated by sink strength. Carbon translocationbetween two compartments depends on the gradient of assimilateconcentration. The gradient induces carbon translocation fromthe most to the least concentrated compartment, except for thevacuole compartment into which translocation is possible whateverthe concentration gradient. Fruit growth, in terms of freshweight, results from the phloem water supplied to the fruitaccording to the concentration gradient between the fruit andthe stem. The model is calibrated for peach trees by comparingobserved and simulated fruit dry and fresh weights for a shootwith normal fruit load. The model simulates variability betweenpeach fruits and the effect of contrasting fruit loads. Accordingto this model, photosynthesis increases and assimilate concentrationsin leaves and phloem decrease with decreasing leaf:fruit ratioas reported in the literature. Simulated concentrations of assimilatesin the phloem range from 2 to 14%. Simulated concentration gradientsand specific mass transfer for peach trees range from 0.05 to0.17 g cm^-3m^-1and from 0 to 3 g cm^-2h^-1, respectively, and areof the same order of magnitude as those reported for variousother tree species. The model is used to analyse the effectof fruit position relative to the leaves. Copyright 1999 Annalsof Botany Company Peach tree, Prunus persica (L.) Batsch, model, carbohydrates, translocation, source-sink, fruit.     

Short and Long Term Fluctuations of the Leaf Mass Per Area of Tomato Plants--Implications for Growth Models

The leaf mass per unit leaf area (LMA) is a key variable inmany growth models, since it is often used to predict leaf areaexpansion from leaf dry weight increase, orvice versa. Influencesof source-sink balance on leaf area, leaf dry weight, LMA, andleaf content in non-structural carbohydrates were investigatedin glasshouse tomato crops. The source-sink balance was manipulatedby artificial shading, CO₂enrichment or fruit removal usingdifferent tomato cultivars. Leaf area was hardly affected bycompetition for assimilates except under extreme conditions.In contrast, leaf dry weight, and consequently LMA, underwentlarge and rapid fluctuations in response to any factor thatchanged source and sink activities. A 60% reduction of photosyntheticallyactive radiation involved a 24% decrease in LMA after 10 d.Carbon dioxide enrichment and fruit removal induced about a45% and 15% increase in LMA, respectively, on plants with twofruiting trusses, but hardly affected LMA of producing plants.No significant cultivar effect could be identified. Changesin starch and soluble sugar content in leaves accounted foronly 29% of diurnal variations in LMA, suggesting regular fluctuationsof other components. We propose that structural LMA varies betweena maximum and a minimum value according to the ratio of assimilatesupply and demand during leaf development. Leaf area is independentof the supply of assimilates when the minimum structural LMAis realised. When the maximum structural LMA is attained, astorage pool of assimilates may accumulate in leaves duringperiods of high supply and low demand. We present a model includingthese hypotheses, which predicts structural and non-structuralLMA variations of plants with different source-sink ratios.Copyright1998 Annals of Botany Company Tomato,Lycopersicon esculentumMill., SLA, SLW, leaf growth, vegetative sink strength, assimilate competition, source-sink ratio, non-structural carbohydrate, models.     

Enhanced inflorescence development in bougainvillea "san diego red" by removal of young leaves and cytokinin treatments

Removal of young leaves and application of the cytokinin, N-benzyla-α-(tetrahydro-2H-pyran-2yl)-adenine promote inflorescence development in Bougainvillea “San Diego Red”. Defoliation greatly increased the amount of assimilate accumulated at the shoot tip 1 to 2 days after treatment. Cytokinin applications further increased the amount accumulated and this increase was apparent 4 days before morphological changes could be detected at the inflorescence axes. Short days promoted inflorescence development and also increased assimilate accumulation at the reproductive axes; thus, it is suggested that the role of short day induction in bougainvillea may be that of redirecting the flow of assimilates, perhaps by its influence on cytokinin synthesis and distribution.     

A Carbon 14 Study of Metabolism in Tall Fescue Seedlings Acclimating to Growth at Low Temperatures

The youngest fully expanded leaves of young plants of tall fescue(Festuca arundinacea Schreb. cv. S 170) were allowed to assimilate¹⁴CO₂ either (a) at the fifth leaf stage immediately beforetransfer from 17/14?C to 7/4?C (non-acclimated), or (b) aftertransfer from 17/14?C to 7/4?C at the fifth leaf stage, andfurther development in 7/4?C of one or two more leaves (acclimationfor one or two plastochrons). Controls were maintained in 17/14?C and allowed to assimilate ¹⁴CO₂ at the corresponding (fifth,sixth, or seventh) leaf stages. Allocation of 14C amongst sinksand biochemical fractions was analysed during a subsequent periodof growth at 7/4 ?C (cold) or 17/14 ?C (control). Allocationof assimilate to growing parts of the shoot was less than controlsin the non-acclimated plants transferred to the cold and morethan controls in plants acclimated for one plastochron. Afterthe imbalance induced initially by transfer from 17/14?C to7/4 ?C, acclimation for one or two plastochrons brought theallocation amongst sinks and amongst biochemical fates closerto the balance existing in controls. The main shoot and sidetillers differed in the time during acclimation when they becamemore like the controls. The percentage of assimilate in thesoluble carbohydrate fraction of non-acclimated plants and ofplants acclimated for one plastochron, was higher than in controls.The percentage of assimilate in the cell wall fraction was lowerin non-acclimated plants than in controls but the differencefrom controls after two plastochrons acclimation again was less.During the first plastochron after transfer to cold, diversionof assimilate to a reserve pool in sinks could be a factor limitingcell wall synthesis and growth and this limitation may be relievedwhen the reserve pool is ‘full’. Low temperaturereduced the percentage of assimilate in the protein fractionof growing parts of the shoot and the difference was found evenafter two plastochrons acclimation. Key words: Low temperature, metabolism, tall fescue (Festuca arundinacea Schreb. cv. S. 170)     

Seasonal development of annual shoots in some terrestrial orchids from Russia and Japan

Annual shoots of 46 terrestrial orchid species commonly found in wide ranges of temperate climates in Russia and Japan change their patterns of growth recurrence from the dormancy state, through formation and growth, to the next dormancy state during the course of yearly response to seasonal cycles of environmental conditions. Each of the species has its own strategy in seasonal development of aerial shoots, rhizomes, tubers and roots, and shows seasonal differentiation of shoot morphogenesis at the early stage of new shoot apex formation in accordance with its growth habit, habitat and range size of geographical distribution. Perennial orchids with sympodial growth patterns and primitive life forms are characterized by long duration of shoot and inflorescence development inside the bud. Among the species studied, the orchids that have annually regenerating root-stem tubers have the shortest duration of root and shoot morphogenesis. The species that have predominant patterns of monopodial growth show variability in duration of lateral shoot growth due to the energy budget of the mother plant. The species which have latitudinally long ranges of distribution from northern colder regions to southern warmer regions tend to take longer for shoot development inside the bud, and aerial shoots have a shorter life-span in the northern regions than those in the south.     

Regulation of Assimilate Translocation Between Leaves and Fruits in the Tomato

Simultaneous measurement of export from leaves and import tofruits were made on tomato plants reduced to one fully expandedleaf and one fruit. Experimental leaves were exposed to sixlight flux densities (0.5–100 W m^–2) for 24 h whilerapidly growing fruits were kept in the dark at 22 °C. The rates of export of assimilate from these leaves varied from70 to 120 mg C leaf^–1 day^–1 corresponding with ratesof carbon fixation from 3 to 290 mg C leaf^–1 day^–1.Export from leaves with the lowest carbon fixation rates weremaintained by a loss of up to one-sixth of their initial carbon.In contrast, leaves with the highest carbon fixation rates exportedonly half the newly fixed carbon. The rates of import of assimilate to similar-sized fruits (c.16 cm³) were between 80 and 110 mg C fr^–1 day^–1but differed from the export rates of the source leaves. Thespecific growth rates and the specific respiration rates ofthe fruits were related to their initial carbon content at thebeginning of the experiment. Thus, over 24 h, the rate of importwas predetermined by the developmental stage of the fruit unalteredby the rate of current carbon fixation in the source leaf. Translocationof assimilate was regulated by sink demand under both source-and sink-limiting conditions in this short-term situation. The dynamic relationship between assimilate production in leavesand its utilization in fruits is discussed together with therole of sucrose concentration in these organs in regulatingtransport. Lycopersicon esculentumL, tomato assimilate translocation, source-sink relationships     

Assimilation of 14CO2, Assimilate Translocation and Grain Yield in Three Primitive Nepalese Varieties and a European Cultivar (Senta) of Six-row Barley (Hordeum vulgare L.)

Three primitive varieties of six-row barley from Nepal withdifferent degrees of awn development were compared with a bredEuropean cultivar, Senta, under glasshouse conditions, fromanthesis onwards. Apart from the flag leaf the last three mainshoot leaves of the Nepalese varieties were smaller than thoseof Senta, and the lower leaves did not become senescent duringthe first 3 weeks of grain filling. In all varieties the penultimateleaf was the major assimilatory organ but in Senta the relativecontribution of the awns increased with time as the leaves senescedand fixed almost half of the total ¹⁴C assimilated by the shoot.Whereas the supply of assimilate to the ear increased with timein Senta, the reverse was found for the Nepalese varieties andoverall a smaller proportion of assimilate was supplied to theear in these varieties. The grain yield of the main shoot earof the two Nepalese varieties studied in detail was one-thirdof that of Senta; there were only approximately half the numberof grains in each median and lateral row of the ear and thegrains were smaller. There was no correlation between the degreeof awn development or the pattern of awn arrangement withinthe ear and the size of individual grains. The total biomassof the Nepalese varieties was much lower than that of Sentabut there were no differences in the harvest index or in tillerproduction. However, the Nepalese varieties, in contrast toSenta, had a mean grain yield per tiller comparable to thatof their main shoot and thus it appears that selection by plantbreeding may have increased the dominance of the main shoot. Hordeum vulgare L., barley, primitive barley varieties, carbon dioxide assimilation, assimilate translocation, grain filling     

SYMMETRY AND DEVELOPMENT OF BUTOMUS UMBELLATUS (BUTOMACEAE) AND LIMNOCHARIS FLAVA (LIMNOCHARITACEAE)

The prostrate rhizome of Butomus umbellatus produces branch primordia of two sorts, inflorescence primordia and nonprecocious vegetative lateral buds. The inflorescence primordia form precociously by the bifurcation of the apical meristem of the rhizome, whereas the non-precocious vegetative buds are formed away from the apical meristem. The rhizome normally produces a branch in the axial of each foliage leaf. However, it is unclear whether the rhizome is a monopodial or a sympodial structure. Lateral buds are produced on the inflorescence of B. umbellatus either by the bifurcation or trifurcation of apical meristems. The inflorescence consists of monochasial units as well as units of greater complexity, and certain of the flower buds lack subtending bracts. The upright vegetative axis of Limnocharis flava has sympodial growth and produces evicted branch primordia solely by meristematic bifurcation. Only certain leaves of the axis are associated with evicted branch primordia and each such primordium gives rise to an inflorescence. The flowers of L. flava are borne in a cincinnus and, although the inflorescence is simpler than that of Butomus umbellatus, the two inflorescences appear to conform to a fundamental body plan. The ultimate bud on the inflorescence of Limnocharis flava always forms a vegetative shoot, and the inflorescence may also produce supernumerary vegetative buds. Butomus umbellatus and Limnocharis flava exhibit a high degree of mirror image symmetry.