Hormonal Regulation of the Distribution of 14C-labelled Assimilates in the Flowering Shoot of Carnation

Evidence is presented that growth substances have a role indirecting the movement of assimilates towards the developingflowers of carnation. Removal of the terminal flower resultedin decreased upward movement of ¹⁴C-labelled assimilates froma source leaf on the flowering shoot. Applications of indole-3yl-aceticacid or gibberellic acid to the stump of the flower stem partiallyrestored the pattern of movement to that found in the intactshoot. Two gibberellin-like substances and one auxin-like substancewere detected in extracts of the floral tissues. Levels of growthsubstances appeared to be higher in the flower than elsewherein the flowering shoot.     

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     

The Distribution Pattern of 14Carbon Assimilated by the Third Leaf of Wheat

The third leaf of wheat, variety Jufy I, was allowed to assimilate¹⁴CO₂ for 2 hrs.; after a further hour the distribution patternof the assimilates was determined. Uptake of ¹⁴CO₂ and assimilatesleaving the leaf increased until the leaf was fully expanded,then slowly decreased. High proportions of labelled translocates were recorded in boththe stem and the the root system, that in the roots increasinggreatly as movement of translocates to the leaves decreased.The two fully grown leaves, L₁ and L₂, imported only slightamounts of labelled translocates. Movement of labelled translocateto each of the younger leaves in turn occurred in a strikingpattern, such that import into a given leaf reached a maximumwhich coincided with its maximum rate of growth, subsequentlyfalling rapidly and reaching a very low level by the time theleaf is fully grown. The results are discussed in relation to what is known of thegeneral pattern of growth and translocation in the wheat plant.     

氮素对日光温室独本菊品种‘神马’干物质分配影响的模拟

 为定量研究氮素对日光温室独本菊(Dendranthema morifolium)干物质分配的影响, 该研究以独本菊品种‘神马’为试验材料, 于2005年10月～2006年7月在北京日光温室内进行了不同定植期和不同氮素水平的栽培试验, 以生理辐热积为发育尺度, 定量分析了氮素对独本菊品种‘神马’干物质分配指数动态的影响, 建立了氮素对日光温室独本菊品种‘神马’干物质分配影响的模拟模型, 并用与建立模型相独立的数据对模型进行了检验。结果表明, 独本菊品种‘神马’叶片累积氮含量最大值出现在现蕾期, 现蕾期叶片累积氮含量适宜值为1.62 g•m^–2。模型对日光温室独本菊品种‘神马’各器官干重预测结果较好, 茎、叶和花干重的预测值与实测值之间基于1:1线的决定系数分别为0.94、0.97和0.94, 相对预测误差分别为10.3%、5.76%和4.02%。该研究建立的模型可以根据温室内的气温、太阳辐射、日长和现蕾期叶片累积氮含量预测日光温室独本菊品种‘神马’各个器官干重随生育时期的动态变化, 从而为日光温室独本菊品种‘神马’生产中氮素的优化管理提供决策支持。     

Pattern and Control of Distribution of 14C-assimilates in Reproductive Plants of Lolium multiflorum Lam. var. Westerwoldicum

The distribution of ¹⁴C-assimilates was examined in reproductiveplants of Lolium multiflorum Lam. var. Westerwoldicum (cv. Tama)from which all emerged tillers had been removed, leaving themain tiller with two expanding leaves, one of them the flagleaf, and two expanded leaves. Export of ¹⁴C from the lowerexpanded leaf was mainly to the tiller in its axil, the steminternode below its node and the roots, whereas the upper expandedleaf supplied predominantly the expanding leaves, the ear, steminternodes, roots and the tiller bud in the axil of the lowerleaf. Defoliation and root-pruning showed that expanding leaveswere able to compete successfully for assimilates, probablythrough the production of substances capable of mobilizing supply.Local application of 1-naphthaleneacetic acid (NAA), gibberellicacid (GA₃) and 6-benzylaminopurine (BAP) to small tiller budsshowed that GA³ and BAP promoted bud growth and ¹⁴C accumulation,but that addition of NAA reduced these effects.     

Effects of Growth Retardants, Gibberellic Acid and Indol-3-ylacetic Acid on Stem Extension and Flower Development in the Pot Chrysanthemum (Chrysanthemum morifolium Ramat)

The growth retardants chlorphonium chloride, daminozide anda new, quaternary ammonium compound, piproctanyl bromide, allreduced shoot length and delayed the time of flowering of thepot chrysanthemum (Chrysanthemum morifolium Ramat) cv. BrightGolden Anne grown throughout in short days. The retardants delayedflowering by reducing the rate of flower bud development andnot by influencing bud initiation. In the case of chlorphoniumchloride and daminozide, a single dose of 20 or 40 µggibberellic acid (GA) completely overcame the effects on bothstem length and flowering, whereas when piproctanyl bromidehad been applied GA did not always bring about a total reversal.Responses to GA were recorded a few days after its application.Neither the retardants nor Ga altered leaf number. Only whenpiproctanyl bromide was the retardant did indol-3-ylacetic acidproduce a small but significant increase in stem length at flowering. The results are consistent with a theory of retardant actionin which gibberellins play the dominant role and strongly suggestthat these hormones are a major factor influencing both stemextension and the rate of flower-bud development in the chrysanthemum.They may promote flower development and thus hasten floweringby attracting assimilates to these organs. Chrysanthemum morifolium Ramat, stem extension, flower development, growth retardants, gibberellic acid, indol-3-ylacetic acid     

Assimilate Distribution in Poa annua L.

The carbon economy of a flowering tiller of Poa annua L. hasbeen examined over the period from inflorescence emergence tograin shedding. The total import of ¹⁴C by the inflorescencereached a maximum at late grain filling but the relative importof assimilate was greatest 14 days after its appearance andrepresented 20–25 per cent of that assimilated by theinflorescence itself. The inflorescence continued to be an importantassimilatory organ after grain ripening when it exported morethan 50 per cent of its assimilate to the stem, roots and othertillers. The patterns of distribution of assimilates from the youngestuppermost and the oldest green leaf of the reproductive tillerwere largely determined by the stage of development of the inflorescence.The youngest leaf mainly supported the inflorescence up to theend of the grain-filling stage but then supplied assimilatesbasally to the roots and adjacent tillers. The oldest greenleaf supported the growth of the stem and the inflorescenceup to anthesis but after this supplied assimilates mainly tothe roots and tillers. Removal of grains or the entire inflorescence only 1 h beforesupplying ¹⁴CO₂ greatly reduced the rate of fixation of ¹⁴CO₂and the export of radiocarbon, as well as changing the patternof distribution of assimilates within the plant. The significanceof these results is discussed and comparisons made with cerealsand perennial grasses.     

Translocation of 14C-Assimilates in Roses

Movement of ¹⁴C-assimilates from young and mature leaves to young rose shoots (Rosa hybrida cv. Marimba) was examined in two developmental stages. In the first stage after bud breaking the young shoot, especially its tip, depends for its supply of assimilates mainly on the mature foliage. At this stage young leaves are powerful sinks and retain 97% of their own photosynthates. The translocated 3% move mainly to the roots. At a later stage, just after the appearance of the flower bud, most of the leaves on the shoot become a source. The upper leaves supply assimilates to the flower bud and to the upper part of the stem. The ¹⁴C-assimilates from the lower leaves move in two directions, the larger part being directed downward.     

The Export and Distribution of 14C-labelled Assimilates from each Leaf on the Shoot of Lolium temulentum during Reproductive and Vegetative Growth

In both reproductive and vegetative plants of Lolium temulentumL., the export of ¹⁴C-labelled assimilates from each healthyleaf on the main shoot to terminal meristem, stem, tillers,and roots was measured each time a new leaf was expanded, fora period of 5 to 6 weeks. Some labelled assimilates moved fromeach leaf on the main shoot to every meristem in the same shoot,as well as to the tops and roots of adjacent organically attachedtillers. The terminal meristem of the reproductive shoot, which includedthe developing inflorescence, received 70–80 per centof the carbon assimilated by the emerged portion of the growingleaf, 15–25 per cent of the carbon assimilated by thetwo youngest expanded leaves, and 5–10 per cent of thatfrom each of the older leaves. A similar pattern of carbon supplyto the terminal meristem was found in vegetative shoots, exceptthat older leaves on young vegetative shoots supplied even lessof their carbon to the terminal meristem. The general conclusionis that developing leaves at the tip of the shoot receive aboutthe same proportion of carbon from each leaf as does a developinginflorescence. Young expanded leaves provided most labelled assimilates forstem growth; during both reproductive and vegetative growth,expanded leaves increased their export of labelled carbon tostem, and exported less of their ¹⁴C to roots and sometimesto tillers. In these reproductive and vegetative shoots, grown in a constantexternal environment, the major changes in the pattern of distributionof labelled assimilates appeared to be the result of increasedmeristematic activity in stem internodes; the development ofan inflorescence had no obvious direct effect on the carboneconomy of shoots.     

Effects of Kinetin on Growth of the Apical Meristem and Floral Differentiation in Chenopodium rubrum L.

Kinetin (1•10^–4 M and 1•10^–3 M) was appliedto the plumules of 6-day-old Chenopodium rubrum plants. Effectson growth, anatomical structure and organogenesis in the apicalmeristem were followed. Floral differentiation as affected bykinetin was also investigated in plants induced to flower byshort-day treatment. Kinetin increased mitotic activity in the apical meristems inboth induced and non-induced plants. The effect was most pronouncedin the peripheral and subcentral zone. An increase in nucleolussize and a higher degree of pyroninophilia in the peripheralzone was also observed, indicating a localized promotion ofRNA synthesis. A higher rate of leaf initiation and a stimulationof leaf and stem growth was subse quentiy recorded. The growthof axillary meristems and of bud primordia was promoted onlyat the lower concentration of kinetin (1•^10–4 M),in both photoperiodically-induced and non-induced plants. However,the pattern of lateral bud growth differed from that found innormal floral differentiation. In kinetintreated plants, thebud primordia are isolated from the summit of the shoot apexby a succession of rapidly growing leaves. The enhancement ofleaf growth leads to correlative inhibition of axillary budpriniordia and results, finally, in a suppression of floraldifferentiation. The inhibitory effect of kinetin on floweringwas compared with that of auxin. Inhibition of flowering occurredin both cases but is achieved in two different ways.     

The Distribution and Identity of Assimilates in Tomato with Special Reference to Stem Reserves

Much of the work on the distribution of ¹⁴C-labelled assimilatesin tomato has been done in winter under low light intensities,and consequently the reported distribution patterns of ¹⁴C maynot be representative of plants growing in high light. Further,there are several somewhat conflicting reports on patterns ofdistribution of ¹⁴C-assimilates in young tomato plants. We soughtto clarify the situation by studying the distribution of ¹⁴C-assimilatesin tomato plants of various ages grown in summer when the lightintensity was high. In addition, the role of the stem as a storageorgan for carbon was assessed by (a) identifying the chemicalfractions in the stem internode below a fed leaf and monitoring¹⁴ C activity in these fractions over a period of 49 d, and(b) measuring concentrations of unlabelled carbohydrates inthe stem over the life of the plant. The patterns of distribution of ¹⁴C-assimilates we found fortomato grown under high light intensity confirmed some of thosedescribed for plants grown under low light, but export of ¹⁴Cby fed leaves was generally higher than reported for much ofthe earlier work. Lower leaves of young plants exported over50% of the ¹⁴C they fixed, although export fell sharply as theplants aged. Initially, the roots and apical tuft were strongsinks for assimilates, but they had declined in importance bythe time plants reached the nine-leaf stage. On the other hand,the stem became progressively more important as a sink for ¹⁴C-assimilates.Older, lower leaves exported more of their ¹⁴C-assimilates tothe upper part of the plant than to the roots, whereas youngleaves near the top of the plant exported more of their assimilatesto the roots. The stem internode immediately below a fed leafhad about twice the ¹⁴C activity of the internode above theleaf. Mature leaves above and below a fed leaf rarely importedmuch ¹⁴C, even when in the correct phyllotactic relationshipto the fed leaf. In the first 3 d after feeding leaf 5 of nine-leaf plants, theorganic and amino acid pools and the neutral fraction of theinternode below the fed leaf had most of the ¹⁴C activity, butby 49 d after feeding, the ethanolic-insoluble, starch and lipidfractions had most of the ¹⁴C activity. Glucose, fructose andsucrose were the main sugars in the stem. Although concentrationsof these sugars and starch declined in the stem as the plantsmatured, there was little evidence to indicate their use infruit production. Stems of plants defoliated at the 44-leafstage had lower concentrations of sugars and starch at maturity,and produced less fruit than the controls. It was concludedthat tomato is sink rather than source limited with respectto carbon assimilates, and that the storage of carbon in thestem for a long period is possibly a residual perennial traitin tomato.Copyright 1994, 1999 Academic Press Lycopersicon esculentum, tomato, assimilate distribution, ¹⁴C, internode storage, sink-source relationships, starch, stem reserves, sugars     

Tiller Bud Suppression in Reproductive Plants of Lolium multiflorum Lam. Cv. Westerwoldicum

The control of tiller bud growth during reproductive developmentwas investigated in experimental plants ofLolium multiflorumLam. cv. Westerwoldicum that were reduced to a main axis havinga developing but unemerged ear, elongating stem internodes,a series of expanded leaves, slow-growing tiller buds and aroot system. Isolation of the ear by excision of its base, ordecapitation so as to remove the ear together with the upperleaves, promoted the movement of ¹⁴C-assimilates to tiller buds,decapitation being the more effective treatment. Applicationof 0.1 per cent indol–3yl-acetic acid (IAA) to cut tissuesof decapitated plants diverted ¹⁴C-assimilates to upper internodesbut did not reduce import by buds, whereas application of 1.0per cent IAA both diverted labelled assimilates to upper internodesand reduced bud import. Radioactivity from [¹⁴C] IAA appliedto the upper leaves or to the ear base was recovered from budsin very small amounts; larger amounts were recovered from budsfollowing the application of labelled IAA to an elongating internode,especially from the bud at the base of the treated internode.It is suggested that tiller bud suppression may be influencedby the movement of inhibitory levels of auxin into buds fromnearby elongating stem internodes, whose activity in turn maybe controlled by the developing inflorescence and upper leaves.     

Effect of Temperature on Carbohydrate Metabolism in Potato Plants

The effect of temperature on partitioning of newly fixed ¹⁴Cbetween the various carbohydrate fractions was studied in differentplant organs of three potato varieties. Incorporation of ¹⁴Cinto starch in the tubers was reduced at high temperatures,but the amount of labelled sucrose increased. In all varietiesthe incorporation of ¹⁴C into the cell wall components in theapex of the plant and in the stem, as well as its incorporationinto starch in the stem, was increased at high temperatures.The variety Norchip, which was found to be less sensitive tohigh temperature as indicated by carbon translocation to thetubers, was found to be less affected also in terms of ¹⁴C incorporationinto starch in the tubers. We suggest that high temperatureaffects carbon metabolism in the various plant organs and theresulting changes are associated with the change in the partitioningof assimilates between these organs.     

Cold hardiness in various organs and tissues of Rhododendron species and the supercooling ability of flower buds as the most susceptible organ

The freezing resistance of various organs and tissues was determined in 24 Rhododendron species (mainly Subgenus Tsutsutsi) having different ecological distributions. The order of hardiness for organ or tissue is as follows: leaf bud > wood ≧ bark > flower bud, and the flower bud is characterized as the most cold-susceptible organ. The relationship of killing temperature (KT) to northern distribution was the most significant in leaf buds compared to other organs and tissues. KTs of leaf buds for the most hardy species were ?45 °C (or below) and those for the most tender species were about ?23 °C, while KTs of flower buds were about ?28 °C for the former and ?16 °C for the latter. Although KTs of flower buds native to southwestern Japan were well correlated with the exothermic temperature distribution (ETD) of florets, those in the more northern species were generally lower than ETDs. The supercooling ability of flower buds appears to be sufficient to avoid the freezing stress since the extreme minimum temperature (EMT) at the northern limit of natural distribution for each tree species examined was not lower than the KT and ETD of the flower buds.     

The Translocation of 14C-Labelled Assimilates in Tomato Plants Infected with Alternaria Solani (Ell. and Mart.) Jones and Grout

A quantitative study was made of the effect of infection bya facultative parasite, Alternaria solani, on the translocationof ¹⁴C-labelled assimilates in the tomato plant. In a plantwith a single diseased leaf, this leaf retained a greater proportionof its assimilated radiocarbon during the early stages of infection.The export of assimilates from a diseased leaf when diseasedevelopment was purposely retarded and was found to be similarto that from a control leaf. At a late stage in the disease,where there was extensive chlorosis and necrosis, export fromdiseased leaves was generally increased and the distributionof the translocated assimilates was altered. Non-infected leaveswere at first unaffected by the disease, but later there wasincreased contribution to the actively growing regions of theplant. In some cases there was a slight increase in total exportfrom healthy leaves but, more generally, a change in the distributionof assimilates occurred. In particular, there was a consistentincrease in activity in the roots. This response to infectionwas not related to the amount of disease present. No evidencewas obtained for an increased import into infected leaves fromnon-infected leaves at any stage of the disease.     

Effects of Leaf Infections by Septoria nodorum Berk. on the Translocation of 14C-labelled Assimilates in Spring Wheat

The influence of infection with Septoria nodorum of leaves belowthe flag leaf on the translocation of ¹⁴C-labelled assimilatesin wheat was followed. In the vegetative phase export of assimilatesfrom a single infected leaf was reduced, but export from a healthyleaf on a heavily infected plant was increased. During the reproductivephase export from leaves was not affected by disease. Heavyleaf infection had little effect on the patterns of distributionof export especially during reproductive growth when only changesin the proportion of assimilates in leaf sheaths and tillerstumps were found. Distribution of export from a healthy flagleaf on an otherwise heavily infected plant was unaltered. Duringvegetative growth changes in the distribution of assimilateswere more marked, the greatest changes occurring when a singleinfected leaf on a healthy plant was exposed to ¹⁴CO₂.     

Preliminary Experiments on the Effect of Temperature on the Movement of 14C-labelled Assimilates through the Phloem of Willow

Experiments were performed on both young shoots of willow (3–5weeks old) and mature stems which had been growing for a periodof 2–3 years. ¹⁴CO₂ was supplied to the leaves, and themass transport of the labelled assimilates through a portionof the stem enclosed in a temperature-controlled jacket wasmeasured by determining the slope of the rise in the activityof huneydew collected from a colony of the aphid Tuberolachnussalignus (Gmelin). It was found that there was a marked difference in the behaviourof the young shoots and mature stems. In the former, a fallin temperature slowed the transport, whilst in the latter acomparable fall in temperature increased the transport. Possiblecauses for these effects have been suggested, and the resultsare discussed in relation to published work on temperature effects.     

Distribution of leaf assimilates in the stem of Picea abies L.

Summary Autoradiographic and microautoradiographic studies of 2-year-old Picea abies plants show that in summer leaf assimilates from the second-year shoot are translocated basipetally. Leaf assimilates are first transported to the stem via leaf trace phloem, then to the base of the stem in the sieve cells of the latest increment of secondary phloem. On the way down leaf assimilates move radially from sieve cells into cells of the phloem parenchyma, the vascular cambium, the rays, the inner periderm and certain cells of pith and cortex, including the epithelial cells surrounding the resin ducts. Other cells of pith and cortex remain nearly free of label, despite the long translocation time (20 h). With the exception of the vascular cambial cells, the stem cells that gain leaf assimilates by radial distribution coincide with those that contain chlorophyll and starch.     

Some Effects of Yellow Rust (Puccinia striiformis) on 14Carbon Assimilation and Translocation in Wheat

A well-developed infection of Yellow Rust on a leaf of springwheat (Jufy I) caused the assimilation of ¹⁴CO₂ by that leafto decrease to 43.5 per cent of that of an uninfected leaf.Over a period of three hours translocation of ¹⁴C from an infectedleaf was only 0.87 per cent of that from a control leaf. Whencontrol plants were kept in the light for periods up to 16 hoursafter assimilating ¹⁴CO₂ translocation continued at a steadyrate, whereas there was only negligible translocation from infectedleaves after the first few hours. The retention of labelledassimilates in the infected leaf could be partly, but not completely,accounted for by a conversion of assimilates to an alcohol-insolubleform. Rust infection had no effect on the distribution patternof ¹⁴C to other leaves from one which had assimilated ¹⁴CO₂.In contrast to the marked retention of assimilate by an infectedleaf, such a leaf was unable to distort the normal distributionby attracting assimilates from the other leaves.     

基于色谱技术的款冬花蕾与花梗代谢组成差异分析

本研究拟对款冬花蕾与花梗的化学组成差异进行比较。采用基于气质联用的代谢组学技术对花蕾与花梗的代谢组成差异进行分析,代谢产物的结构指认通过NIST数据库检索和标准品对照确定,GC-MS数据通过XCMS预处理后导入SIMCA-P软件进行多元统计分析;采用超高效液相色谱法对花蕾和花梗中吡咯里西啶生物碱的含量进行测定。结果基于GC-MS的代谢组学分析共鉴定了款冬中54个代谢产物,主成分分析显示款冬花蕾与花梗的代谢组成明显不同。OPLS-DA分析的载荷图显示,与花蕾相比,花梗中肌醇、香橙烯、豆甾醇、棕榈酸等化合物含量较低,而蔗糖、花生四烯酸等含量较高。此外,花蕾中吡咯里西啶生物碱含量为102μg·g-1,明显高于花梗中的含量(64μg·g-1)。款冬花蕾与花梗的化学组成存在较大差异,为了保证中医临床用药的安全有效,药用款冬花中应剔除花梗,并在质量标准检查项中规定花梗限量。