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.     

Effects of Sulphur Dioxide and Nitrogen Dioxide on Growth and Translocation in Winter Wheat

Gould, R. P. and Mansfield, T. A. 1988. Effects of sulphur dioxideand nitrogen dioxide on growth and translocation in winter wheat.—J. exp. Bot 39: 389–99 Winter wheat (Triticum aestivum L. cv. Avalon) was grown undersimulated autumn conditions for 4 weeks and exposed to a mixtureof SO₂ and NO₂. Biomass was measured after 2, 3 and 4 weeksand the flag leaves of sample plants were labelled with ¹⁴CO₂.Biomass yields revealed an increase in shoot-to-root ratiosunder polluted conditions. The labelling experiments showedthat less assimilate was transported to the roots, whilst morewas allocated to the younger components of the plant. It appearedthat NO₂ and SO₂ also caused labelled photosynthate to be retainedin the labelled leaf. Reducing the photon flux exacerbated theeffects of SO₂ and NO₂ as indicated by changes in biomass andby the distribution of ¹⁴C. Key words: Wheat, SO₂, NO₂, growth, translocation     

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.     

Distribution of Assimilates from Various Source Leaves During the Development of Gladiolus grandiflorus

The distribution pattern of the products of photosynthesis wasstudied in gladiolus plants (Gladiolus grandiflorus cv Eurovision)in four stages of development I, plants having a very younginflorescence still enclosed between the leaves; II, plantswith a young inflorescence just emerged from the leaves, III,plants at full bloom, IV, plants with young fruits. The first,third or sixth foliage leaf was labelled with ¹⁴CO₂, and subsequentdistribution in the plant was determined Results were expressedas a percentage of translocated ¹⁴C accumulated by each partof the plant which gives a measure of its ‘sink strength’,or as ‘relative sink activity’ (RSA) which is independentof the size of the indicated organ. There are two competing sinks in the developing gladiolus—theinflorescence and the new corm. When RSA is the criterton theinflorescence constitutes the main sink irrespective of thesource leaf from the first stage until flowering. With the subsequentwilting of the flowers and fruit set RSA of the inflorescencedeclines rapidly and the new corm becomes the main sink When‘sink strength’ is the criterton it appears thatthe inflorescence acts as a very weak sink when it is youngand becomes increasingly stronger until flowering and then declinessteeply. Sink strength of the corm declines during the developmentof the inflorescence and then increases again steeply with wiltingof the flowers and fruit set. There are small differences betweenthe various source leaves. The young new corm acts as a strongsink for the lower foliage leaf and progressively weaker forupper leaves. Gladiolus grandiflorus, flower development, corm, assimilates distribution, sink strength, relative sink activity     

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.     

Factors Influencing Alanine Aminotransferase Activity in Leaves of Lolium temulentumL.: II. EFFECTS OF GROWTH REGULATORS AND PROTEIN BIOSYNTHESIS INHIBITORS

Effects of kinetin (K), gibberellin A₃ (GA₃), and 2-(chloroethyl)-trimethylammoniumchloride (CCC) on levels of alanine aminotransferase (GPT) andrates of protein synthesis were studied with both intact plantsand isolated leaf segments of Lolium temulentum L. In intactplants CCC stimulated and CA₃ reduced GPT activity, the effectsbsing much greater in 8.h than in 16-h photoporiods. CCC showedmaximum stimulatory effects at 10^–2 M and K at 5 x 10⁵M. No effect of GA₃ could be demonstrated with concentrationsup to 10^–4M. Both K and CCC retarded GPT decline in leafsections, the latter without associated effects upon pigmentbreakdown. Cycloheximide was highly effective in reducing proteinsynthesis in leaf sections. A close correlation between rateof protein synthesis and GPT activity was found over an inhibitorconcentration range from 10^–6 to 10^–4 M. The resultsare discussed in terms of possible methods of in vivo regulationof GPT activity.     

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

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

Dormancy in Dioscorea: Generality of gibberellin-induced dormancy in asexual dormant organs

Effects of GA₃ and CCC application on the sprouting of bulbilsor subterranean dormant organs of 10 species in the genus Dioscoreawere observed. Although the efficiency of both chemicals differedby species, in general GA₃ inhibited and CCC promoted the sproutingof the above dormant organs. In some species, however, dilutedGA₃ (0.003–0.3 µM) has a promotive and diluted CCC(3–30 µM) has an inhibitive effect on sprouting. Effects of GA₃ application on shoot elongation were tested onsprouted bulbils. GA₃ promoted elongation when applied directlyto the shoots and inhibited it when applied to the bulbous parts. These results suggest that GA activates two opposing reactions—sprouting-promotingand sprouting-inhibiting—in these organs. The complicatedrelation between GA₃ or CCC concentrations and sprouting wereexplainable by assuming that the two counteractive reactionswere activated by GA in different degrees. ¹ Present address: Department of Biology, Faculty of Science,Yamagata University, Yamagata 990, Japan. (Received June 21, 1976; )     

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.     

Effects of Nitrogen Fertilizer on the Distribution of Photosynthate during Grain Growth of Spring Wheat

The distribution of photosynthate labelled with ¹⁴C was studiedin spring wheat grown with different amounts of nitrogen fertilizerin the three years 1972–4, after exposing the flag leafor the leaf below the flag leaf to ¹⁴CO₂ at 6–10 or 19–26days after anthesis. The movement of ¹⁴C to ears was unaffectedby nitrogen fertilizer except after early exposure in 1973,when nitrogen increased the retention of ¹⁴C in stems at maturity The concentration of sugar in the top part of the shoot at theend of the day was unaffected by nitrogen in 1973, but at 22days after anthesis in 1974 the concentration of sucrose inthe glumes and rachis, and in the flag leaf lamina was increasedby nitrogen. Loss of sugar by translocation and respirationduring the night may explain why this increase in concentrationwas not reflected in the ¹⁴C distribution 24 h after supplying¹⁴C. The proportion of the total ¹⁴C content of the shoot that wasin the ear at maturity ranged from 68 to 95 per cent dependingon when and to which leaf the ¹⁴CO₂ was supplied. Less than5 per cent remained in the leaf exposed to ¹⁴CO₂. The proportionof the final ear weight contributed by the leaf below the flagleaf was about half that contributed by the flag leaf. In 1974 about 24 per cent of the ¹⁴C absorbed by the flag leaf,and 56 per cent of that absorbed by the second leaf, was lostby maturity, presumably by respiration. Most loss occurred inthe first 24 h.     

Factors Affecting Uptake of Radioactive Phosphorus by Leaves and its Translocation to other Parts of the Plant

The rate of uptake of ³²P from labelled NaH₂PO₄ solutions sprayedon to one leaf of swedes (Brassica napus) or French beans (Phaseolusvulgaris) was rapid during the first few hours and fell to zeroafter 4 days. ²²P was detected in the root after 3 hours andcontinued to move out of the treated leaf for at least 6 daysafter application. A larger fraction of the applied ³²P wasabsorbed from repeated than from a single spraying. Swedes absorbed more ³²P from a single application to the lowersurface than to the upper surface of the leaf. Doubling theconcentration of the spray caused a small increase in the percentageof applied ²²P that was absorbed. Absorption by French-beanleaves decreased slightly when the area sprayed with a constantamount of ³²P was doubled, and decreased with increasing ageof leaf. Increasing the phosphorus supply to the roots of swedesaffected neither the initial rate nor the total amount of ³²Puptake by the leaves but decreased the quantity of ³²P thatwas translocated out of the treated leaf. Increasing the relative humidity of the air around the plantsalso increased³²P uptake. Shading usually decreased uptake andalways decreased translocation. Rewetting the leaf to whichthe ³²P had been applied, with water or sucrose solution, hadvariable effects. The significance of the results is discussed.     

Distribution of Assimilates in Gladiolus grandiflorus as Affected by Water Deficit

The distribution patterns of photosynthesis products derivedfrom ¹⁴CO₂ and of applied ¹⁴C-sucrose were studied in floweringgladiolus plants (Gladiolus grandiflorus cv. Eurovision) irrigatednormally or water stressed. Even small stresses led to a decreasein the mobilizing ability of the inflorescence and an increasein that of the corm. The stress caused a great reduction in¹⁴CO₂ fixation, and, to a lesser degree, a delay in assimilatetranslocation out of the source leaves. In all cases, well irrigatedor stressed, the corms had the highest water potential (leastnegative), followed by the inflorescences and the leaves. Thegreater the stress, the greater were the differences betweenthose organs. It is proposed that under water deficit the waterpotential of the main sink (inflorescence) decreases and itsturgor dependent growth is slowed down, so reducing its mobilizingability, and causing delayed translocation out of the leaves.The water potential of the corm — the competitive sink— remains high enabling its growth to continue and assimilatesare attracted to it. ¹⁴C-distribution, corm, flower, Gladiolus grandiflorus, water deficit, water potential     

Translocation in Sugar-beet: I. ASSIMILATION OF 14CO2 AND DISTRIBUTION OF MATERIALS FROM LEAVES

¹⁴CO₂ was supplied to leaves, and movement of labelled carbonto other parts of the plant was assessed. Young growing leavesutilized assimilated carbon for their own growth and did notexport carbon to the rest of the plant, while fully expandedleaves exported much of their photosynthate, both to root andto young leaves. Translocation from a particular leaf was tothe two or three younger leaves on the same side of the plant,and to a sector of root below the source leaf. Specific distributionto growing leaves could be modified by partial defoliation.There was no movement of material to leaves which had emergedbefore the source leaf. Part of the carbon entering a leaf by assimilation (and, foryoung leaves, by translocation) was incorporated into insolublematerial, especially in young leaves. Some of the carbon enteringa developing root was permanently stored as sucrose, althoughmuch also entered insoluble material. Loss from the leaf ofcarbon fixed during a short period of photosynthesis was rapidat first but continued at a decreasing rate for several days.Some carbon fixed into the insoluble fraction was translocatedfrom the leaf later, during senescence. Sucrose was the mainmaterial translocated immediately after photosynthesis.     

Morphogenetic Effects on Vegetative Plants of Poa pratensis L. of 6-Azauracil, (2-Chloroethyl)- phosphonic acid, and (2-Chloroethyl) trimethyl-ammonium chloride and their Interaction with Gibberellic Acid

Fresh and dry weights and leaf size of Poa pratensis were reducedwhen treated with 6-azauracil (AzU), (2-chloroethyl)phosphonicacid (CEPA), or (2-chloroethyl)trimethylammonium chloride (CCC).AzU and CEPA inhibited epidermal cell division without inhibitingcell elongation, while CCC inhibited mainly cell elongationand cell division to a small extent. The ratio of blade lengthto sheath length and the blade length/width ratio were reduced,but leaf emergence and tillering were increased by AzU and CEPA.CCC affected only the latter three features. Like GA₃, CEPAinduced stem formation, but internodes were shorter. GA₃ was ineffective in preventing leaf-growth inhibition byAzU, which inhibited Ga₃-induced cell elongation. The inhibitoryeffect of CEPA on leaf growth was apparently reversed by GA₃,but this was due solely to increased cell elongation, the reductionin cell number being unaffected. Ga₃ reversed the effect ofCCC on leaf length, as well as on cell size and number. Simultaneousapplication of the inhibitors produced a complex interactionin reducing leaf length and number and size of epidermis cells.It is postulated that AzU, CEPA, and CCC have different modesof action because they have specific effects on plant growthand different effects on GA₃-induced cell elongation.     

14C Fixation and Translocation in Sugarcane Clones with Contrasting Weights of Leaf per Unit Weight of Cane and Storage Cell Volumes

The rates of ¹⁴CO₂ fixation and translocation of labelled assimilatesin the leaf below the topmost fully expanded leaf of four sugarcaneclones with widely differing weights of leaf per unit weightof cane (L/J ratio) and storage cell volumes, were measuredin the field. Differences in the rate of fixation and rate andvelocity of translocation were found between the clones and,within species groups, the former only was related to the L/Jratio and to storage cell volume A possible restriction of translocationthrough the Lamina/sheath junction (dewlap), indicated by abuild up of radioactivity just distal to the dewlap, occurredin two clones and it is suggested that the efficiency of translocationthrough the dewlap is another factor which may influence thephotosynthetic rate of sugarcane leaves. The effects of self-shading on the relationship between fixationby leaves near the top of the canopy and assimilation rate ofsingle stalks are discussed. Saccharum officinale, sugarcane, carbon fixation, assimilation, translocation     

Translocation in Plants Possessing Supernumerary Phloem: II. THE INCLUDED PHLOEM OF BOUGAINVILLEA GLABRA CHOISY AND THE BICOLATERAL BUNDLES OF CUCUMBER (CUCUMIS SATIVUS L.)

The translocation path in the included phloem of Bougainvilleaand in the bicolateral bundles of cucumber was studied by exposingyoung branches to ¹⁴CO₂ and detecting the radioactive compoundsby autoradiography. In Bougainvillea, the structure and functionof the phloem system is comparatively uncomplicated and uniform.All phloem bundles, i. e. those which are located in parenchymatoustissue of the central zone and those embedded in the secondaryxylem, become labelled. Exogenous IAA was translocated in thebundles, but the exact mode of translocation was not ascertained.Apical dominance was not affected by girdling. The implicationof this fact is discussed with respect to the translocationof the auxin that determines the correlative inhibition involvedin apical dominance. In cucumber the inner phloem became labelled throughout theplant to a lesser extent than the outer phloem. However, inthe petiole of the assimilating leaf the intensity of the labelwas the same in both inner and outer phloem, although the innerphloem has fewer elements. Below the treated leaf the innerphloem translocated less than the outer phloem. Above this leafthe inner phloem was entirely unlabelled     

Effects of Plant Growth Regulators on Grain-filling and Yield of Rice

Effects of three phytohormones (IAA₁, GA₃ and kinetin) on grain-fillingand the pattern of ³²P translocation from individual leavesto grains were studied at intervals of 7 days during the progressof reproductive development of rice (Oryza saliva L. cv. Jaya).The plants were sprayed with 100 µg ml^–1 aqueoussolutions of the hormones at 100 days, when the plants wereentering the reproductive stage. Kinetin produced a pronouncedeffect on grain-filling as well as on ³²P mobilization fromindividual leaf to grains and increased yield, possibly by increasingleaf longevity. GA₃ and IAA also increased the grain-fillingand ³²P mobilization significantly over control but the effectswere less marked than those of kinetin. Oryza sativa L., rice, grain yield, translocation, growth regulators, gibberellic acid, indol-3-yl acetic acid, kinetin     

EVIDENCE ON THE SITE OF ACTION OF GROWTH RETARDANTS

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

电子束辐射唐菖蒲球茎对M1叶片的影响初探

为了探讨电子束对唐菖蒲诱变育种的可行性和不同剂量的电子束对叶片的影响;用能量为3MeV的不同剂量电子束辐照唐菖蒲“超级”球茎,对其M1代的叶片进行了研究。 光合作用率,蒸腾速率,细胞间隙CO₂浓度和气孔导度等光合指标在低剂量时变化均不明显,随着剂量的增价,辐照对蒸腾速率和气孔导度起到明显的刺激作用并达到0.05的显著水平;通过对电子束处理后唐菖蒲叶片叶绿素含量的测定表明,叶绿素含量及叶绿素a/b比值均发生了变化,并且叶绿素a含量在240Gy处理后达到最大值,且达到了0.05的显著水平;扫描电镜观察发现,高剂量处理的M1代植株表皮毛与气孔结构均发生改变,叶表面组织特征明显排列杂乱不规则。由此表明,电子束辐照对唐菖蒲叶片的形态与生理均能产生明显的影响。     

The Partitioning of Photosynthetically Assimilated 14C into Amino Acids in Wheat 1. Partitioning During Transport to the Grain

When ¹⁴CO₂ was fed to flag leaf laminae at 20 d post-anthesis,the transport organs between the leaf and the grains containedappreciable ¹⁴C in glutamine, glutamate, serine, alanine, threonineand glycine. Smaller amounts of ¹⁴C were present in gamma-aminobutyricacid (GABA), aspartate and cysteine. Other amino acids whichwere labelled in the source leaf were not labelled in the transportorgans. The export of labelled glutamine, serine, glycine andthreonine from the source leaf was favoured in comparison tothe other amino acids mentioned. Threonine accumulated, andwas subsequently metabolised, in the rachis. [¹⁴C]GABA alsoaccumulated in the rachis. In the grains, the relative amountof soluble [¹⁴C]alanine increased with chase time. This wasprobably due to de novo synthesis and reflected the specialrole of alanine in grain nitrogen metabolism. Wheat, Triticum aestivum, ¹⁴CO₂, amino acids, transport, carbon metabolism