Translocation Of Photosynthates Research Articles

Environmental Effects on Photorespiration of C3-C4 Species

The possibility of altering CO(2) exchange of C(3)-C(4) species by growing them under various CO(2) and O(2) concentrations was examined. Growth under CO(2) concentrations of 100, 350, and 750 micromoles per mole had no significant effect on CO(2) exchange characteristics or leaf anatomy of Flaveria pringlei (C(3)), Flaveria floridana (C(3)-C(4)), or Flaveria trinervia (C(4)). Carboxylation efficiency and CO(2) compensation concentrations in leaves of F. floridana developed under the different CO(2) concentrations were intermediate to F. pringlei and F. trinervia. When grown for 12 days at an O(2) concentration of 20 millimoles per mole, apparent photosynthesis was strongly inhibited in Panicum milioides (C(3)-C(4)) and to a lesser degree in Panicum laxum (C(3)). In P. milioides, acute starch buildup was observed microscopically in both mesophyll and bundle sheath cells. Even after only 4 days exposure to 20 millimoles per mole O(2), the presence of starch was more pronounced in leaf cross-sections of P. milioides compared to those at 100 and 210 millimoles per mole. Even though this observation suggests that P. milioides has a different response to low O(2) with respect to translocation of photosynthate or sink activity than C(3) species, the concentration of total available carbohydrate increased in shoots of all species by 33% or more when grown at low O(2). This accumulation occurred even though relative growth rates of Festuca arundinacea (C(3)) and P. milioides grown for 4 days at 210 millimoles per mole O(2), were inhibited 83 and 37%, respectively, when compared to plants grown at 20 millimoles per mole O(2).

Nectar Accumulation in Flowers of Fireweed,Epilobium Angustifolium(Onagraceae), in Response to Simulated Defoliation

SummaryThe amount of nectar accumulating in inflorescences of defoliated and intact shoots of fireweed from which pollinators were excluded for a 14- to 16-h period was assayed by timing the visits of bees and recording the numbers of flowers visited. The day following a defoliation of c. 80% of leaf area, there was a 42% reduction in the mean time spent per flower by bees, relative to undamaged controls. No further reductions were evident, 2, 3 or 5 days postdefoliation; defoliated shoots maintained a nectar secretion rate of c. 58% that of controls. Although under normal circumstances most photosynthate for nectar secretion is provided by adjacent leaves, these results suggest that the sink effect of open flowers is sufficient to mobilize the translocation of photosynthate from distant plant pans. Defoliated plants did not significantly reduce the numbers of flowers open until day 3 postdefoliation, and even then, there were no differences in the numbers of flowers visited by bees. Parallel fluctuations...

Photosynthate translocation during union development in Picea grafts

Rootstocks (Piceaabies (L.) Karst.) and scions (Piceapungens Engelm.) were labelled separately during graft union development with 14CO2 and translocation of the labelled photosynthate determined qualitatively and quantitatively. Rootstock photosynthates did not cross the graft union after scion budbreak had started. Total recovery of labelled scion photosynthates in scions declined from nearly 60% to less than 10% during the 1st week after grafting, and did not increase until xylem connections were established 1-2 weeks before budbreak. Less than 2% of the recovery from the scion was found in the graft union before scion budbreak. Most of the label recovered before scion budbreak was in the needle sugar fraction. After budbreak, most of the label was recovered in elongating buds.

Dinitrogen fixation, ureide concentration in xylem exudate and translocation of photosynthates in soybean as influenced by pod removal and defoliation

Abstract Effects of pod removal and defoliation on the growth, dinitrogen-fixing activity, ureide concentration in xylem exudate and nodules, and translocation of photosynthates in soybean (Glycine max (L.) Merr. cv. Tamahomare) were examined and the following results were obtained. 1. Dinitrogen-fixing activity decreased significantly by both pod removal and defoliation.2. The concentration of sugars and starch in the nodules increased by pod removal but decreased by complete defoliation, while it did not change by partial defoliation.3. The ureide concentration in the xylem exudate and nodules increased by pod removal, especially by complete defoliation.4. Pod removal led to a decrease in the export rate of 14C from leaf but had no effect on 14C distribution percentage in the nodules.5. Exudation rate of ureide-14C in the xylem sap was lower during the first hour after the exposure to 14CO2 and thereafter it was higher in depodded than in control plants. From these results, it is suggested that the factor controlling of the dinitrogen-fixing activity of soybean under ordinary field conditions is presumably not the status of the photo-synthate supply to the nodules but, the export rate of the fixed-N from nodules.

Kentucky Bluegrass Photosynthate Partitioning Following Scheduled Mowing

Abstract The distribution of photosynthetically fixed carbon within a turfgrass sod was investigated following a routine mowing. The partitioning of 14C-labeled photosynthate was monitored in Kentucky bluegrass (Poa pratensis L. cvs. Baron and Merion) turf 2, 24, and 72 hr after mowing at 3.8 cm. Circles of turf (15 cm in diameter) were exposed to 14CO2 for 15 min, 10-cm-diameter plugs were removed 2 and 24 hr after exposure, and the plants were assayed for radioactivity. Experiments were conducted in late spring, midsummer, and early autumn for 2 years in field plots on a silt loam. Photosynthate translocation from leaf blades to leaf sheaths and crowns was reduced by as much as 25% within 2 hr after mowing but generally returned to a constant and greater rate within 24 hr. Midsummer mowing temporarily inhibited photosynthate transport more than mowing in spring or fall. Photosynthate distribution within turfgrass plants was influenced more by time of year and nutritional status than by mowing. Kentucky bluegrass maintained as closely mowed turf sustains only a slight and temporary disturbance in energy partitioning in response to mowing.

Effect of salinity on translocation of assimilates in french bean

The effect of sodium chloride and sodium sulphate salinities on the rate of translocation of photosynthates in french bean at the pod filling stage was investigated. Both salt treatments exerted a negative influence on the translocation of photosynthetic assimilates and in this respect the NaCl treatment was more detrimental than that of Na2SO4. The transport of radioactivity from the source to the sink (pod) and other plant parts such as leaves, stem and roots was adversely affected by both salinity regimes.

Jasmonic Acid in Different Parts of the Developing Soybean Fruit

In Glycine max (L.) Merr. cv. G7R-315 the endogenous levels of jasmonic acid (JA) were studied in the pericarp (vascular bundles and remaining part) and seed parts (hilum, testa, cotyledons, embryo axis) at four different stages of fruit development. The quantitation of JA has bcen done by radioimmunoassay after chromatographic purification of the ethyl acetate extracts on DEAE-Sephadex A-25. The highest concentrations of JA were determined in the vascular bundles of the pericarp at all stages investigated. Somewhat smaller amounts were found in the hilum and tests of the seed. These three fruit parts contain the major vascular system for phloem translocation of photosynthates. Lowest JA concentrations were found in the cotyledons and embryo axes during the whole development of fruits. The results are discussed with respect to the possible role of JA in assimilate translocation and pericarp senescence.

Determination of potential yield-limiting factors of soybeans using SOYMOD/OARDC

SOYMOD, a computer model of the soybean plant, was upgraded and used to simulate growth at the plant part level. Sensitivity analyses were conducted on twenty-six plant parameters and on three weather parameters. The results showed excellent consistency and indicated that translocation of photosynthate to the root system and the efficiency of use of this photosynthate to produce assimilated nitrogen compounds are of considerable importance in determining eventual plant yield. In particular, those parameters that controlled the plant processes that competed with translocation for allocation of photosynthate (i.e. stem growth rate) had the largest effects on plant productivity. On the basis of these results, several suggestions for potential genetic modifications in order to achieve an ‘ideal’ soybean plant are presented. The results and suggestions should serve as useful guidelines for future research efforts.

Impact of symbiotic algae on sea anemone metabolism: analysis by in vivo 31P nuclear magnetic resonance spectroscopy.

High-field pulsed Fourier-transform nuclear magnetic resonance spectroscopy (NMR) was used to quantify the adenylate levels of sea anemones (Aiptasia pulchella) with and without symbiotic dinoflagellates (Symbiodinium sp.). Animals were fed to repletion, then starved in darkness for up to six days before collection of in vivo NMR spectra. The host adenylate ratio of ATP: (ATP + ADP) declined significantly with increasing periods of starvation in both symbiotic and aposymbiotic hosts (P less than 0.05). However, the decline in the animal adenylate ratio was significantly more rapid in animals bearing symbiotic algae (P less than 0.05). This suggests that symbiotic algae in darkness cause more rapid depletion of host energy reserves, possibly by drawing on host pools of organic substrates. In vivo NMR spectroscopy was also used to evaluate the effect on A. pulchella of photosynthesis by zooxanthellae. Symbiotic anemones were fed to repletion, then starved under high irradiance (300 to 320 mu Ein m-2 s-1) or low irradiance (70 to 80 mu Ein m-2 s-1) conditions for up to five days. The host adenylate ratio declined significantly (P less than 0.01) with starvation under both treatments, but no significant difference was detected between treatments (P greater than 0.35). Blotted wet weight of anemones under high and low irradiance declined by 50% over eight days of starvation, but there was no significant difference in the rate of weight loss by anemones in the two treatments. There results suggest that translocation of photosynthate from symbiotic zooxanthellae does not significantly affect host adenylate ratio or have a sparing effect on host biomass during starvation in this symbiotic sea anemone.

Evidence of competition for photosynthates between growth processes and oleoresin synthesis in Pinus taeda L.

A group of 10 pines (Pinus taeda L.) in a 35-year-old stand in Central Louisiana was sampled periodically from March through December 1984 for oleoresin flow from small wounds. Oleoresin yield was closely associated with periods of calculated moderate soil water deficit and presumed growth reduction. The period of maximum oleoresin flow coincided with the period of calculated maximum soil water depletion. Calculated potential evapotranspiration reached a maximum in late June, but water deficits did not reach maximum levels until September. Apparently, moderate seasonal water deficits that limit growth, but do not limit photosynthesis and translocation of photosynthates, favor differentiation processes, such as oleoresin synthesis. Because oleoresin is a primary defense against southern pine beetle (Dendroctonus frontalis Zimm.) attack in pines, recognition of these relationships should contribute to an understanding of southern pine beetle-host tree interactions.

ブドウ′デラウェア′における光合成産物の転流形態

Various 14C-compounds were used in this study to clarify the form in which photosynthates were translocated during Stage III of grape berry (cv. ′Delaware′) development. The compounds used were sucrose-14C-(U), glucose-14C-(U), fructose-14C-(U), malic acid-14C-(U), tartaric acid-14C-(U), leucine-14C-(U) and alanine-14C-(U). During Stage III, sugars are accumulated very rapidly in grape berries. One hour after the application of labelled sugars, organic acids and amino acids to the mesophyll, 25% of sucrose, 29% of glucose, 16% of fructose, 42% of malic acid, 80% of tartaric acid, 47% of leucine and 28% of alanine had moved into the petiole without transformation.When incorporated from the petiole 75cm from the cluster, 8% of sucrose, 77% of glucose, 71% of fructose, 14% of malic acid, 38% of tartaric acid, 28% of leucine and 17% of alanine moved into the berries without transformation two hours after the application. The speed of translocation of applied 14C-compounds differed. Labelled sugars, organic acids and amino acids were interconverted in leaves, shoots and berries.The translocation of photosynthates from leaf to berry in ′Delaware′ grape probably occurs in the form of sugars, organic acids and amino acids.

パイナップルの物質生産に関する研究(乾物生産と収量成立過程について)

Dry matter production in pineapple plants which were transplanted to the field in September could be divided into four stages: 1) the first stage of early plant growth; 2) the second stage of middle plant growth; 3) the third stage of fruitlet differentiation; 4) the fourth stage of fruitlet growth. These stages were strongly affected by the climate of the season.At harvest, the total dry weight per plant of ‘Mitsubishi’ was heavier than that of ‘Hawaii’. However, the dry weight of the fruit was lower. This shows that translocation of photosynthates to the fruit was more active in ‘Hawaii’ than in ‘Mitsubishi’.Leaf area index (LAI) increased rapidly in the latter half of the second stage and reached a maximum of 6.5 in the third stage. The maximum value remained almost unchanged until the fourth stage.Seasonal changes of the crop growth rate (CGR) showed bimodal curves with two peaks. The first peak appeared in the second stage (October) and the second one in the fourth stage from May to June. The maximum CGR was 8.1-8.2gm-2Net assimilation rate (NAR) were similar to those of CGR. Maximum NAR was observed in the second stage (August) and the value was 2.40 to 2.55gm-2 day-1. NAR was largest when the LAI was 2 to 3. CGR reached a maximum when LAI was 3 to 4. Optimum LAI was estimated to be 3.01.Relative growth rate (RGR) was closely correlated with NAR. Efficiency of solar energy utilization was 0.2% in the first stage and reached a maximum of 1.2% in December. Flower bud initiation began from this time.Active accumulation of photosynthates in the fruit was observed when LAI was kept at 3.01 and when flower bud induction treatment was practiced. Analyses of dry matter production of pineapple plants and the structure of the community showed that to achieve a short leaf length and narrow angle of leaf emergence were necessary community with high productivity. Thus, breeding should be carried out to select plants with these characteristics.

Low night temperature effect on photosynthate translocation of two C4 grasses.

Translocation of assimilates in plants of Echinochloa crus-galli, from Quebec and Mississippi, and of Eleusine indica from Mississippi was monitored, before and after night chilling, using radioactive tracing with the short-life isotope 11C. Plants were grown at 28°/22°C (day/night temperatures) under either 350 or 675 μl·l-1 CO2. Low night temperature reduced translocation mainly by increasing the turn-over times of the export pool. E. crus-galli plants from Mississippi were the most susceptible to chilling; translocation being completely inhibited by exposure for one night to 7°C at 350 μl·l-1 CO2. Overall, plants from Quebec were the most tolerant to chilling-stress. For plants of all three populations, growth under CO2 enrichment resulted in higher 11C activity in the leaf phloem. High CO2 concentrations also seemed to buffer the transport system against chilling injuries.

Physiological influences on carbon isotope discrimination in huon pine (Lagarostrobos franklinii)

Measurements of the light environment and stomatal and photosynthetic behaviour are reported for Huon Pine (Lagarostrobos franklinii, family Podocarpaceae) in western Tasmanian rainforest. For a variety of microenvironments, these are used in an analysis of stable carbon isotope measurements in the air, and in branch and leaf material, using a model for carbon isotope fractionation in leaves (Farquhar et al. 1982).The major features of δ13C variations with respect to branch position can be explained in terms of the direct influence of light level acting via the rate of CO2 assimilation. In addition a relatively constant δ13C gradient of about 2.6‰ between leaf tip and branch wood is observed.Alternative explanations are advanced for the tip-towood gradient in δ13C. If the δ13C of leaf tips is taken to represent the value for photosynthate, maintenance respiration is proposed as a mechanism for the further fractionation; a significant 13C depletion in respired CO2 is implied which is not supported by indirect measurements of atmospheric isotope ratio. Furthermore, an assumption of significant sampling errors (e.g. related to humidity effects on assimilation) is required to obtain good quantitative prediction of the light influence.If the branch wood δ13C is taken to represent that of the photosynthate, the tip-to-wood gradient may find an explanation, via the model, in terms of tip tissue comprising carbon from immature cells. Translocation of photosynthate from exposed to shaded branches is then proposed as a means of obtaining quantitative agreement with the predicted light influence.The support provided for the applicability of the Farqunar et al. (1982) model in the field is discussed in the context of the problem of obtaining past global atmospheric CO2 levels from δ13C in tree-rings.

Translocation of Photosynthates into Vacuoles in Spinach Leaf Protoplasts

A method was developed for the isolation of vacuoles from the mesophyll protoplasts of spinach leaf, employing the discontinuous Ficoll density gradient centrifugation technique. Isolated vacuole preparations were judged to be free from other organellar fractions based on the assays of marker enzyme activities of individual organelles.Using this isolation method, a time-dependent translocation of (14)C-labeled photosynthates into vacuoles was determined. In contrast to a significant transport of (14)C organic acids such as malate and citrate within 10 to 15 minutes (14)C neutral sugars and amino acids were barely transported into vacuoles during 40 minutes incubation, in spite of the fact that a relatively large amount of these compounds are found in the vacuoles. It was also found that a majority of [(14)C]sucrose remains in the cytosol, apparently not actively moving into the vacuoles. Overall results appear to suggest that vacuoles are not actively engaged in photosynthetic carbon metabolism in spinach leaf protoplasts.

Translocation of photoassimilate from leaves of two popyploid genotypes of tall fescue differing in photosynthetic rates

The photosynthetic rate of a decaploid genotype (1‐16‐2) of tall fescue (Festuca arundinacea Schreb.) is about twice that of a common hexaploid genotype (V6‐802) (Plant Physiol. 72: 16–21, 1983). Translocation of photosynthate out of the leaves is a possible means of regulating carbon assimilation. To evaluate this possibility, we have examined a) translocation velocity, b) time course of translocation from leaves, c) photoassimilate partitioning pattern into whole plants in pulse and chase experiments, and d) interveinal distances between two ploidy genotypes. Most of the 14C accumulated in sucrose, and the labelled carbon moved down the leaf blades at similar velocities (6 to 10 cm h−1) in both genotypes. Recent 14C assimilate was rapidly translocated from the fed area of the leaf blade. For example, the decaploid and the common hexaploid had translocated 40 and 26% of the 14C, respectively, at 6 h, and 79 and 49% of the 14C, respectively, at 24 h. Partitioning of 14C among plant organs was considerably different between the genotypes after a 24 h chase. For example, out of the total 14C recovered from the whole plant, the decaploid had retained 40% in the labelled leaf with 10, 33 and 29% in other leaves, stem bases and roots, respectively; whereas the hexaploid had retained 91% in the labelled leaf with 4, 3 and 2% in other leaves, stem bases and roots, respectively. However, the higher rate of translocation was correlated with greater interveinal distances in the decaploid genotype. These results suggested that the higher translocation percentage in the decaploid than the hexaploid genotype was due to greater sink activity.

Translocation of 14C Photosynthates in Castor Plants (Ricinus communis L.) during the Growing Stages of the Lateral Branches

Translocation of 14C Photosynthates in Castor Plants (Ricinus communis L.) during the Growing Stages of the Lateral Branches

Translocation of photosynthate during reproductive stage of corn hybrids differing in prolificacy.

[in Japanese]

Incorporation of 14CO2 into carbohydrates in the developing kernels of triticale (×Triticosecale Wittmack) in relation to kernel shrivelling

Abstract Flag leaves of a triticale which has shrivelled kernels, IMJ-3, and those of a better kernel type, S 71–142, were allowed to photosynthesize in 14 CO 2 at two stages of kernel development. On a per plant basis, the incorporation of 14 C in the watersoluble fraction decreased while the ethanol-insoluble fraction increased with age in both lines. The incorporation of 14 C into starch in the kernel was limited in the cultivar with the shrivelled kernels, although there was considerable sucrose available in the whole ear. Therefore, the problem of kernel shrivelling seems to reside in the kernel itself rather than in translocation of photosynthate from source to sink.

Photosynthesis and Translocation Rate in Arachis hypogaea L. Mutants

Summary Photosynthesis and translocation rate of photosynthate have been studied in groundnut (Arachis hypogaea) mutants TG-1 and TG-16 and their parent Spanish Improved at different stages of growth. Photosynthetic rate per plant was significantly higher in mutants as compared with their parent, with TG-1 being the most efficient. The translocation of 14C-labelled photosynthate to nodules in mutants was also higher than the parent. The lower kernel yield in mutant TG-1, which had high rates of photosynthesis, appears to be due mainly to poor mobilization of photosynthate for kernel development. The comparison of photosynthesis and translocation in TG-1 and TG-16 indicates that mobilization of food rese1ves to developing kernels is important for high yields.