Translocation Of Photoassimilates Research Articles

The Co-Involvement of Light and Air Temperature in Regulation of Sex Expression in Monoecious Cucumber (<i>Cucumis sativus</i> L.)

The combination effects of light and air temperature, which were expressed as photothermal ratio (PTR), on the growth and sex expression of three monoecious cucumbers (Cucumis sativus L. cv. “Xintaimici”, “Jinyan 3” and “Jinyan 4”) were studied with hydroponics in this research. The results showed that with the increase of PTR, different growth responses were observed in the three cucumber cultivars. In contrast, high PTR (H-PTR, 0.86 mol·m-2·degree-day-1) significantly increased the total number of female nodes and decreased the total number of male nodes of the three monoecious cucumber cultivars compared with cucumbers grown under low PTR (L-PTR, 0.64 mol·m-2·degree-day-1). More photoassimilate was partitioned to fruits of three cucumber cultivars with the increase of PTR, indicating that PTR-mediated femaleness of monoecious cucumber might be attributed to the enhancement of photoassimilate translocation from source organs to sink organs.

Evidence of reproductive cost in the triphasic life history of the red alga Gracilaria chilensis (Gracilariales, Rhodophyta)

The extent of changes in basic physiological and demographic traits associated with reproduction was investigated in the highly cultivated haploid–diploid red alga, Gracilaria chilensis. Sixty individuals bearing vegetative and reproductive fronds collected in the natural population of Niebla (39°52′ S, 73°23′ W), in Chile, were cultivated under controlled culture conditions. Our results demonstrated that vegetative fronds have a higher survival rate and a better growth rate than reproductive ones irrespective of the type of individual analyzed (male gametophyte, female gametophyte, and tetrasporophyte). Moreover, the reproductive fronds clearly showed a decrease in photosynthetic activity compared to non-reproductive ones. In males and tetrasporophytes, the photosynthetic reduction in reproductive individuals could be explained by a physical effect of reproductive structure development as well as spores release, disrupting the continuity of the photosynthetic cortical tissues. Translocation of photoassimilates from nearby vegetative tissue or the previous accumulation of photosynthetic products seems to be a prerequisite for reproductive structure development in this species. Altogether, these results document for the first time in G. chilensis that reproduction has a strong physiological effect on male, female, and tetrasporophyte fronds. This trade-off between reproduction, growth, and survival suggest the existence of reproductive costs in the life history of G. chilensis.

Rice grain Fe, Mn and Zn accumulation: How important are flag leaves and seed number?

Flag leaves play an important role in synthesis and translocation of photoassimilates in the rice plant, affecting grain yield; similarly they were believed to be a major source of remobilized minerals for the seeds. At the same time, the seed’s sink strength plays an important role in dry matter accumulation. To investigate the relative contribution of rice flag leaves and seed sink strength to seed mineral accumulation, field experiments were conducted to evaluate the effect of flag leaf or half-seed removal on seed Fe, Mn and Zn concentration and content. Flag leaf or 50% of the seeds were removed at anthesis. Seed Fe, Mn and Zn accumulation were not affected by flag leaf or second leaf removal. Plants with only half of the seeds showed higher Fe and Zn seed concentrations, but similar Mn concentrations. It is concluded that the flag leaf is not necessary for metal remobilization to the seeds and that seed sink strength and seed number have different roles in Fe/Zn and Mn seed concentrations.

Impact of episodic herbivory by the tamarisk leaf beetle on leaf litter nitrogen and stem starch content: A short communication

Tamarisk (Tamarix spp.) has in recent decades come to dominate riparian corridors throughout much of the western U.S. The implementation of biological control, utilizing the tamarisk leaf beetle (Diorhabda spp., particularly Diorhabda carinulata), has focused attention and research on this method for Tamarix suppression. Researchers are just beginning to understand how herbivory by Diorhabda affects Tamarix physiology and nutritional dynamics. The purpose of this study was to investigate whether herbivory by D. carinulata altered leaf litter nitrogen and stem starch content, and if so, how such alteration varied across a gradient of herbivory chronosequence. Leaf litter and stem analysis showed significantly higher levels of both nitrogen and stem starch content in trees that had experienced herbivory by the leaf beetle. However, there were no significant differences in nitrogen or stem starch content based on years of beetle herbivory. Higher levels of nitrogen in leaf litter from beetle-affected trees may be a result of herbivory-induced desiccation and foliar mortality prior to the translocation of nitrogen back into plant reserves. Additionally, higher stem starch may be a result of either phloem damage reducing the translocation of photoassimilates, or an increase in the shunting of carbohydrates to the site of new leaf growth. Finally, the lack of correlation between years of herbivory and both leaf litter nitrogen and stem starch may indicate that as of yet there have not been sufficient defoliation events to yield anticipated host plant impact.

Relationship between hydraulic conductance and citrus dwarfing by the Flying Dragon rootstock (Poncirus trifoliata L. Raft var. monstruosa)

This work studied the hydraulic characteristics and physiological behavior of two trifoliate orange (Poncirus trifoliata L. Raft) varieties—Flying Dragon (FD) and Rubidoux (RT)—with contrasting size-controlling potential when used as rootstocks for citrus trees. Thus, Valencia orange scions growing on RT root system develop about 40 % more biomass than scions on FD. The anatomical study of xylem root tissue of both rootstocks showed that the number of vessels per cross-sectional area in RT almost doubled that found in FD, whereas diameter distribution did not vary significantly. Hydraulic resistance determined in rootstocks, and bud union segments were, respectively, 2- and 3.4-fold higher in trees on FD than in trees on RT. Root systems accounted for 46.5 and 55.2 % of whole-plant hydraulic resistance, whereas bud union segments represented 7.5 and 14.6 % of this parameter, the dwarfing rootstock (FD) having the highest values. Reduced hydraulic conductance in plants on FD rootstock diminished water potential in high evaporative demand periods, causing a reduction in stomatal conductance with respect to plants on RT. This leads to lower net photosynthetic CO2 assimilation, which may affect biomass production. Translocation of 13C-labeled photoassimilates from leaves to roots was lower in plants on FD than in plants on RT, indicating that in the dwarfing rootstock (FD) there may be a vascular resistance to sucrose transport at the budding union level. Findings show that reduced hydraulic conductance may be the main cause of rootstock-induced dwarfing in citrus grafted onto FD.

Movement of fluorescent dyes Lucifer Yellow (LYCH) and carboxyfluorescein (CF) in Medicago truncatula Gaertn. roots and root nodules

Lucifer Yellow (LYCH) and carboxyfluorescein (CF) served in Medicago truncatula roots and root nodules as the markers of apoplastic and symplastic transport, respectively. The aim of this study was to understand better the water and photoassimilate translocation pathways to and within nodules. The present study shows that in damaged roots LYCH moves apoplastically through the vascular elements but it was not detected within the nodule vascular bundles. In intact roots, the outer cortex was strongly labeled but the dye was not present in the interior of intact root nodules. The inwards movement of LYCH was halted in the endodermis. When the dye was introduced into a damaged nodule by infiltration, it spread only in the cell walls and the intercellular spaces up to the inner cortex. Our research showed that in addition to the outer cortex, the inner tissue containing bacteroid-infected cells is also an apoplastic domain. Our results are consistent with the hypothesis that nodules do not receive water from the xylem but get it and photoassimilates from phloem. A comparison between using LYCH and LYCH followed by glutaraldehyde fixation indicates that glutaraldehyde is responsible for fluorescence of some organelles within root nodule cells. The influence of the fixation on nodule fluorescence has not been reported before but must be taken into consideration to avoid errors. An attempt was made to follow carboxyfluorescein (6(5) CF) translocation from leaflets into roots and root nodules. In root nodules, CF was present in all or a couple of vascular bundles (VB), vascular endodermis and some adjacent cells. The leakage of CF from the VBs was observed, which suggests symplastic continuity between the VBs and the nodule parenchyma. The lack of CF in inner tissue was observed. Therefore, photoassimilate entry to the infected region of nodule must involve an apoplastic pathway.

Imaging of Carbon Translocation to Fruit Using Carbon-11-Labeled Carbon Dioxide and Positron Emission Tomography

Carbon kinetics into the fruit is an agricultural issue on the growth and development of the sink organs to be harvested. Particularly, photoassimilate translocation and distribution are important topics for understanding the mechanism. In the present work, carbon-11 ( <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> C) labeled photoassimilate translocation into fruits of tomato has been imaged using carbon-11-labeled carbon dioxide and the positron emission tomography (PET). Dynamice PET data of gradual increasing of <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> C activity and its distribution is acquired quantitatively in intact plant body. This indicates that the 3-D photoassimilate translocation into the fruits is imaged successfully and carbon kinetics is analyzable to understand the plant physiology and nutrition.

Chlorophenoxyacetic acid and chloropyridylphenylurea accelerate translocation of photoassimilates to parthenocarpic and seeded fruits of muskmelon ( Cucumis melo)

We compared the effect of p-chlorophenoxyacetic acid ( p-CPA) and 1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU) on parthenocarpic and seeded muskmelon ( Cucumis melo) fruits in regards to fruit development and the transport of photoassimilates from leaves exposed to 14CO 2 to the developing fruits. Ten days after anthesis (DAA), the fresh weight, total 14C-radioactivity and contents of 14C-sucrose and 14C-fructose were higher in the CPPU-induced parthenocarpic fruits than in seeded fruits. However, at 35 DAA, fresh weight and sucrose content in mesocarp, placenta and empty seeds of the parthenocarpic fruits were lower than in seeded fruits. Also, total 14C-radioactivity and 14C-sugar content of the parthenocarpic fruits were lower as well as the translocation rate of 14C-photoassimilates into these fruits. Application of p-CPA to the parthenocarpic fruits at 10 and 25 DAA increased fresh weight and sugar content. Moreover, these treatments elevated the total 14C-radioactivity, 14C-sucrose content and the translocation rate of 14C-photoassimilates. The 14C-radioactivity along the translocation pathway from leaf to petiole, stem, lateral shoot and peduncle showed a declining pattern but dramatically increased again in the fruits. These results suggest that the fruit's sink strength was regulated by the seed and enhanced by the application of p-CPA.

Real-time whole-plant imaging of 11C translocation using positron-emitting tracer imaging system

Whole-plant imaging for studying the complete carbon kinetics involved in photosynthesis and subsequent photoassimilate translocation and unloading was achieved using a positron-emitting tracer imaging system (PETIS) in combination with 11CO 2 gas tracer. In an experiment with a soybean ( Glycine max cultivar Jack) plant, it was confirmed that the dynamic PETIS image data obtained followed the conservation law for total carbon. Thus, the proposed PETIS technique is a feasible noninvasive and quantitative solution to study the carbon dynamics over an entire plant in environmental and agricultural studies.

Patterns of photoassimilate translocation to reproductive shoots from adjacent shoots in Camellia sasanqua by manipulation of sink-source balance between the shoots

To know to what extent reproductive shoots are autonomous in Camellia sasanqua, we manipulated the sink-source balance between the reproductive shoots and their adjacent shoots by selecting vegetative or reproductive adjacent shoots, or defoliating the reproductive shoots, and photosynthetically labeled adjacent shoots with (13)C. The atom% of (13)C did not increase in the unlabeled shoots that had leaves, whereas that in the defoliated, unlabeled shoot was significantly increased. These results indicated that the pattern of translocation of photoassimilates to adjacent reproductive shoots occurs depending on the sink-source balance between shoots.

Effect of Night Temperature on Photoassimilate Translocation in Different Tomato Ecotypes

Effect of Night Temperature on Photoassimilate Translocation in Different Tomato Ecotypes

Modulation of growth, photosynthetic capacity and water relations in salt stressed wheat plants by exogenously applied 24-epibrassinolide

Brassinosteroids promote the growth of plants and are effective in alleviating adverse effects of abiotic stresses such as salinity and drought. Under saline conditions, improvement in grain yield is more important than simple growth. Previously it was found that although foliar application of brassinosteroids improved growth of wheat plants, it did not increase grain yield. In present study, influence of root applied 24-epibrassinolide was assessed in improving growth and yield of two wheat cultivars. Plants of a salt tolerant (S-24) and a moderately salt sensitive (MH-97) were grown at 0 or 120 mM NaCl in continuously aerated Hoagland’s nutrient solution. Different concentrations of 24-epibrassinolide (0, 0.052, 0.104, 0.156 μM) were also maintained in the solution culture. Exogenous application of 24-epibrassinolide counteracted the salt stress-induced growth and grain yield inhibition of both wheat cultivars. Of the varying 24-epibrassinolide concentrations used, the most effective concentrations for promoting growth were 0.104 and 0.052 μM under normal and saline conditions, respectively. However, root applied 0.052 μM 24-epibrassinolide enhanced the total grain yield and 100 grain weight of salt stressed plants of both cultivars and suggested that total grain yield was mainly increased by increase in grain size which might have been due to 24-epibrassinolide induced increase in translocation of more photoassimilates towards grain. Growth improvement in both cultivars due to root applied 24-epibrassinolide was found to be associated with improved photosynthetic capacity. Changes in photosynthetic rate due to 24-epibrassinolide application were found to be associated with non-stomatal limitations, other than photochemical efficiency of PSII and photosynthetic pigments. Leaf turgor potential found not to be involved in growth promotion.

Incorporation and translocation of 2-deoxy-2-[18F]fluoro-d-glucose in Sorghum bicolor (L.) Moench monitored using a planar positron imaging system

[(18)F]FDG (2-deoxy-2-[(18)F]fluoro-D-glucose) was fed to a sorghum plant [Sorghum bicolor (L.) Moench] from the tip of a leaf and its movement was monitored using a planar positron imaging system (PPIS). [(18)F]FDG was uptaken from the leaf tip and it was translocated to the basal part of the shoots from where it moved to the roots, the tillers and the sheaths. Autoradiographic analysis of the distribution of (18)F, [(18)F]FDG and/or its metabolites showed translocation to the roots, tillers, and to the leaves that were younger than the supplied leaf. Strong labelling was observed in the basal part of the shoots, in the sheaths, the youngest leaf and the root tips. Our results indicate that [(18)F]FDG and/or its metabolites were absorbed from the leaf and translocated to the sites where nutrients are required. This strongly suggests that [(18)F]FDG can be utilised as a tracer to study photoassimilate translocation in the living plant. This is the first report on the use of [(18)F]FDG, which is routinely used as a probe for clinical diagnosis, to study source to sink translocation of metabolites in whole plants in real time.

Real-time Analysis of Photoassimilate Translocation in Intact Eggplant Fruit using 11CO2 and a Positron-emitting Tracer Imaging System

A recently developed positron-emitting tracer imaging system (PETIS) noninvasively produces quantitative real-time images of the movement of various compounds in plants. To clarify the mechanism of the growth and development of the fruit of eggplant (Solanum melongena L.), we fed 11CO2 to a leaf and monitored the translocation of 11C-labeled photoassimilate into the fruit by PETIS. Continuous images of the translocation of [11C]photoassimilate from the leaf to the fruit and inside the fruit were produced, with a shorter time resolution than reported previously. 11C signal intensity in the fruit increased gradually, and its distribution was not uniform. The fruits were sliced after PETIS measurement and exposed to the imaging plates of a bio-imaging analyzer system. The resultant images showed the localization of 11C activity inside the fruit, and indicated that translocation of photoassimilate within the fruit was not uniform. The velocity of photoassimilate translocation in the peduncle and changes in the rate of translocation of photoassimilate in the fruit were estimated by analysis of PETIS data. The velocity of photoassimilate translocation through the peduncle was estimated as 1.17 cm·min−1. About 60 min after the start of 11CO2 feeding, the 11C activity of the fruit began to increase, and by 120 min it had reached about 8% of feeding 11CO2. These results indicate that it took about 60 min for the first [11C]photoassimilates to reach the fruit. Real time observation of photoassimilate translocation within a fruit has never been reported. PETIS may be a powerful tool for revealing the mechanisms of fruit development and maturity.

Emissão de folhas e início de acumulação de amido em raízes de uma variedade de mandioca em função da época de plantio

O número de folhas acumulado (NF) na haste principal está associado com o aparecimento de vários estádios de desenvolvimento da cultura da mandioca. O início de acumulação de amido (IAA) nas raízes tuberosas da mandioca marca o início da translocação dos fotoassimilados para o principal órgão de reserva nessa espécie. O objetivo deste trabalho foi estimar o filocrono e identificar um indicador morfológico baseado no NF para o IAA em mandioca plantada em diferentes épocas. Um experimento a campo foi conduzido em Santa Maria, RS, Brasil, com quatro épocas de plantio (28/09; 11/10; 16/11 e 27/12/2005). A variedade de mandioca usada foi a "RS 13", plantada em baldes de 12 litros, enterrados no espaçamento com 2,0 x 0,8m. O delineamento experimental foi o inteiramente casualizado com 11 repetições. A soma térmica diária (STd, °C dia) foi calculada a partir da emergência e acumulada por: STa = sigmaSTd. O IAA foi determinado nas plantas de cada balde quando uma raiz atingia um diâmetro de 1cm. O NF na data do IAA e o número final de folhas (NFF) até o primeiro simpódio também foram determinados. O filocrono variou de 20,3 a 29,5°C dia folha-1 e seus valores foram maiores quanto mais tardio foi o plantio. O NFF variou entre as épocas de plantio, aumentando com o atraso do plantio. O NF no IAA foi similar nas quatro épocas de plantio e ocorreu quando, em média, o NF corresponde a 20,9 (±1,0) folhas.

13CO2 pulse‐labelling of photoassimilates reveals carbon allocation within and between tree rings

Post-photosynthetic fractionation processes during translocation, storage and remobilization of photoassimilate are closely related to intra-annual sigma13C of tree rings, and understanding how these processes affect tree-ring sigma13C is therefore indispensable for improving the quality of climate reconstruction. Our first objective was to study the relationship between translocation path and phloem grain. We pulse-labelled a branch of Larix gmelinii (Rupr.) Rupr. and later analysed the sigma13C distribution in the stem. A 13C spiral translocation path closely related to the spiral grain was observed. Our second objective was to study the use of remobilized storage material for earlywood formation in spring, which is a suspected cause of the autocorrelation (correlation of ring parameters to the climate in the previous year) observed in (isotope) dendroclimatology. We pulse-labelled whole trees to study how spring, summer and autumn photoassimilate is later used for both earlywood and latewood formation. Analysis of intra-annual sigma13C of the tree rings formed after the labelling revealed that earlywood contained photoassimilate from the previous summer and autumn as well as from the current spring. Latewood was mainly composed of photoassimilate from the current year's summer/autumn, although it also relied on stored material in some cases. These results emphasize the need for separating earlywood and latewood for climate reconstruction work with narrow boreal tree rings.

14CO2 Fixation and Translocation of Photoassimilates as Selection Criteria of Egyptian Taro Genotypes

The growth characteristics, different physiological parameters, photosynthetic activity (14CO2 fixation), and the translocation rate of photoassimilates in different taro (Colocasia esculenta L. Schott) genotypes was studied in order to determine the possible use of these parameters as selection criteria for different widely used genotypes of taro (Delta No. 9, 15, 20, 21, and balady). The results obtained suggest that Delta No. 21 shows the most significant increase in all parameters tested compared with the control (balady), followed by Delta No. 9, 15, and 20, respectively. The results show a positive correlation between photosynthetic activity, translocation efficiency, and total yield. The selected clone Delta No. 21 is recommended for cultivation in the delta region of Egypt. (Managing editor: Ping He)

Intra-colonial response to Acroporid “white syndrome” lesions in tabular Acropora spp. (Scleractinia)

‘White syndrome’ is considered to be the most prevalent coral disease on the Great Barrier Reef, characterised by rapid rates of lesion progression and high levels of colony mortality. This study investigated the production and translocation of photoassimilates towards white syndrome lesions (WSLs) and artificially inflicted lesions in healthy and diseased colonies of tabular Acropora spp. to determine the intra-colonial response to white syndrome using 14C labelling. Translocation of 14C labelled photoassimilates was preferentially orientated away from active WSLs, with minimal 14C activity observed in the lesion borders, whilst artificial lesions (ALs) created directly opposite WSL borders showed significantly higher 14C activity, suggesting active translocation of photoassimilates for tissue regeneration. Transport of photoassimilates in healthy coral colonies was preferentially oriented towards ALs with a higher perimeter–area ratio, although translocation towards WSL boundaries was minimal even though the lesion perimeter was often the width of the colony (>200 cm). We suggest that the preferential orientation of photoassimilates away from WSLs may represent a deliberate strategy by the colony to induce a ‘shutdown reaction’ in order to preserve intra-colonial resources within areas of the colony that are more likely to survive and recover.

Sexual dimorphism ofPseudotectococcus rolliniaeHodgson &amp; Gonçalves 2004 (Hemiptera Coccoidea Eriococcidae) influences gall morphology onRollinia laurifoliaSchltdl. (Annonaceae)

The male and female of Pseudotectococcus rolliniae Hodgson & Gonçalves 2004 induce leaf galls on Rollinia laurifolia Schltdl. The galls occur in similar proportions but are morphologically distinct. This study recorded the occurrence and characterized both morphologically and morphometrically the galls on R. laurifolia. In addition, we evaluated the impact of galls induced by P. rolliniae males and females on the differentiation of the host plant leaf tissues. Galls induced by females were spherical, with an average volume of 36.5 mm1(± 16.9), whereas galls induced by males were conical with an average volume of 3.5 mm3 (± 2.6). Most of the sampled leaves were galled (93.8%). The presence of more than 5 galls per leaf caused the leaf area to be reduced on average by 57.3% compared with ungalled leaves. Leaves with the majority of galls induced by females had a greater area reduction than leaves with the majority of galls induced by males. The reduction of leaf area was directly related to the translocation of photoassimilates to gall sites and their utilization for gall growth. The longer life cycle of the P. rolliniae female and its sessile habit may determine the higher differentiation of leaf tissues involved in the larger growth of these galls.

Environmental and Physiological Studies on Fruit Growth and Mass Accumulation in Fruits of Tomato Plants

Tomato (Lycopersicon esculentum Mill.) fruit production depends on the accumulation of mass (i.e., water, sugar, calcium ion, etc.) in the fruit via phloem and xylem transport. Water accumulation in the fruit is responsible for the fruit expansion growth, that is variable according to the balance between sap flux into the fruit via vascular system and transpiratory water loss from the fruit. Sugar accumulation in the fruit depends on translocation of photoassimilates from leaves through phloem. Salt or water stress treatment in the tomato fruit production is generally provided during the reproductive stage in order to obtain high quality fruits. This treatment leads to the increment of fruit sugar concentration, the restriction of fruit expansion growth and the increase in blossom-end rot. In a previous study on tomato fruit production, analyses of fruit parameters, such as dry matter weight, fresh weight, nutrients, etc., have been carried out using harvested fruits at the intervals of one week or 10 days. However, it is important to demonstrate the dynamics of sap flux with reference to mass accumulation in the fruit. Therefore, three new measurement systems or methods to evaluate the dynamics of mass accumulation in the fruit were developed, and the effects of day-night temperature, water stress, and salt stress on fruit growth and fruit water balance were analyzed.