Wheat Organs Research Articles

Association between Yield and Carbon Isotope Discrimination Value in Different Organs of Durum Wheat Under Drought

AbstractCarbon isotope discrimination (Δ) has been proposed as a selection criterion for transpiration efficiency and grain yield in drought‐prone environments for several C3 species, including cereals. Δ analysis, however, has mainly been concerned with grain or culm tissues and little work has been devoted to other organs. The objective of this study was to describe Δ variation in different organs and to examine the relationships between Δ and grain yield across environments. Six durum wheat genotypes with contrasted grain Δ were cultivated under rainfed conditions during three successive years at Montpellier (South of France). Δ was measured on flag leaf, stalk, awns, chaff and rachis sampled at anthesis and maturity, and on mature grain. Higher genotypic variation and closer correlation with yield were noted for grain Δ compared to other plant parts. The genotype ranking across years was more consistent for grain Δ than for other organs. Consequently, the grain seems the most effective plant part for Δ analysis in durum wheat under Mediterranean conditions. The study of Δ variation in other organs may be useful, however, to evaluate the contribution of those organs to grain filling and final yield according to environmental conditions.

Cloning of thioredoxin h reductase and characterization of the thioredoxin reductase-thioredoxin h system from wheat.

Thioredoxins h are ubiquitous proteins reduced by NADPH- thioredoxin reductase (NTR). They are able to reduce disulphides in target proteins. In monocots, thioredoxins h accumulate at high level in seeds and show a predominant localization in the nucleus of seed cells. These results suggest that the NTR-thioredoxin h system probably plays an important role in seed physiology. To date, the study of this system in monocots is limited by the lack of information about NTR. In the present study, we describe the cloning of a full-length cDNA encoding NTR from wheat ( Triticum aestivum ). The polypeptide deduced from this cDNA shows close similarity to NTRs from Arabidopsis, contains FAD- and NADPH-binding domains and a disulphide probably interacting with the disulphide at the active site of thioredoxin h. Wheat NTR was expressed in Escherichia coli as a His-tagged protein. The absorption spectrum of the purified recombinant protein is typical of flavoenzymes. Furthermore, it showed NADPH-dependent thioredoxin h reduction activity, thus confirming that the cDNA clone reported in the present study encodes wheat NTR. Using the His-tagged NTR and TRXhA (wheat thioredoxin h ), we successfully reconstituted the wheat NTR-thioredoxin h system in vitro, as shown by the insulin reduction assay. A polyclonal antibody was raised against wheat NTR after immunization of rabbits with the purified His-tagged protein. This antibody efficiently detected a single polypeptide of the corresponding molecular mass in seed extracts and it allowed the analysis of the pattern of accumulation of NTR in different wheat organs and developmental stages. NTR shows a wide distribution in wheat, but, surprisingly, its accumulation in seeds is low, in contrast with the level of thioredoxins h.

Characterization of two thioredoxins h with predominant localization in the nucleus of aleurone and scutellum cells of germinating wheat seeds.

Two full-length cDNA clones, designated TrxhA and TrxhB, encoding different but very similar thioredoxin h polypeptides were isolated from wheat (Triticum aestivum cv. Chinese Spring) aleurone cells. The deduced proteins show a high similarity to each other and to thioredoxin h from other sources, in particular from T. aestivum and T. durum. One of them, TRXhA, was expressed in E. coli as a His-tagged polypeptide and used to raise polyclonal antibodies by immunization of rabbits. These antibodies identified a single band (ca. 13.5 kDa) in western blot analysis of protein extracts from all wheat organs analyzed. TRXhA and TRXhB when expressed in E. coli as intact polypetides showed indistinguishable electrophoretic mobility, which corresponded to the 13.5 kDa polypeptide detected in wheat protein extracts. The amount of thioredoxin h transcripts increased in scutellum and aleurone cells during germination but GA3 did not exert any stimulatory effect on thioredoxin h expression. Although northern blot analysis detected a single band, competitive RT-PCR showed that this band is due to the accumulation of both TrxhA and TrxhB mRNAs. These results suggest that the single band detected in western blots is due to the presence of at least two thioredoxin h polypeptides. Immunolocalization experiments confirmed the high content of thioredoxins h in scutellum and aleurone cells, and showed a low content in the starchy endosperm of germinating grains. Interestingly, though these proteins are evenly distributed in the cytosol, the highest levels of thioredoxins h were detected in the nucleus, both in aleurone and scutellum cells.

Productivity and carbon isotope discrimination in durum wheat organs under a Mediterranean climate

For durum wheat, we promote the use of carbon isotope discrimination (Δ) as an indirect selection criterion for transpiration efficiency and grain yield (GY), and we identify the most effective organ for characterising Δ genotypic variation. A field experiment was conducted in the South of France on 144 accessions, with a drought period occurring from February to June. Harvest index (HI), GY and Δ (ΔL, flag leaf; ΔA, awn, ΔG grain) were measured. Significant positive genetic correlations were noted between Δ and both GY and HI. A larger genotypic variation and a higher broad-sense heritability were noted for ΔG compared to ΔL and ΔA. ΔG correlated better with GY and HI than ΔL and ΔA, showing that ΔG could provide a better assessment of genotypic behaviours under drought during grain filling. Moreover, the indirect selection based on ΔG (even when evaluated with one replicate) appeared more efficient than the direct selection for grain yield. This result emphasised the potential value of grain carbon isotope discrimination as a criterion for grain yield improvement under stressed Mediterranean conditions.

Comparative metabolism of famoxadone in fish, plants and animals

The fate and comparative metabolism of famoxadone in fish, plants and animals were evaluated. Famoxadone residues were retained by the fish after exposure (BCF 2800), mainly in the viscera; however, rapid and complete elimination/ depuration of the absorbed residues occurred within seven days after the exposed fish were placed in untreated water. Minimal absorption, translocation, and metabolism of famoxadone were observed in grape and potato plants after foliar treatment. Metabolism of famoxadone in the wheat plants, rats, goats, and poultry was extensive. Transfer of 14 C-residues to the wheat grain, milk, eggs, organs and tissues was minimal. Common metabolic reactions of famoxadone in plants and animals include aryl hydroxylation, cleavage of the anilino-oxazolidine-dione and phenoxy-phenyl ether linkages, opening of the oxazolidinedione ring and conjugation.

Studies on the expression of the wheat prolyl isomerase FKBP73 during plant development

Prolyl isomerases are ubiquitous proteins which accelerate the slow steps of protein folding by isomerisation of peptide bonds in which proline participates. We have isolated and characterised a wheat prolyl isomerase belonging to the FK506 binding protein family (FKBP) named wFKBP73. By using polyclonal antibodies raised against the recombinant wheat FKBP, its expression in wheat organs, during seed imbibition and caryopsis maturation was studied. The highest level of the wFKBP73 expression was found in imbibed embryos and 2 day old seedlings, whereas the protein could not be detected in mature green leaves. When young leaves and roots were dissected into segments, the highest expression was associated with the meristematic region. The wFKBP73 accumulated during seed maturation and was present in dry seeds. Its presence in dry seeds may suggest its importance in assisting correct folding of newly synthesized proteins and maintaining the native structure of certain macromolecules. The wFKBP73 was determined to be a stable protein with a half life of 41 h. The polyclonal antibodies raised against the recombinant protein detected cross reacting proteins in barley, corn, rice, and pea suggesting that the FKBP73 is a conserved protein in plants. The wFKBP locus Xtav1926(Fkbp) was mapped on the short arm of the wheat group seven chromosome.

Influence of phosphorus supply pattern in soil on yield of spring wheat

The purpose of this research was 1) testing the influence of various patterns of supplying phosphorus (P) on dry matter production and biomass allocation in various organs of spring wheat and 2) exploring the optimal P application pattern for high grain yields of spring wheat. Plants were grown in pots constructed with PVC tube, 130 cm long and 10 cm in diameter. Each tube consisted of two segments of 0–43 cm and 43–130 cm. Two soil water regimes were imposed: i) D, water content in the upper soil layer was kept at 50% of field capacity (FC), lower layer (43–130 cm) was at 75–80% of FC and ii) W, a well‐watered control with the entire soil profile being maintained at 75–80 FC. Three P applications were made: i) Pu, P was supplied in the upper 0–43 cm soil layer, ii) Pl, P was supplied in the 43–130 cm layer, and iii) Pe, P was supplied to the entire soil profile. Total photosynthates of plants in WPe and WPu in a whole day were higher than that in DPe and DPu. The photosynthetic rates were similar between WP1 and DPl. The highest P/T (Photosynthesis/ Transpiration) in topsoil drying treatments occurred in DPu, but in wet treatments it was Wpe. The DPu and WPu had similar leaf area, which were significantly higher than other treatments. In the period from the beginning of water treatments to harvest, water consumption in DPe, DPu, DPl, WPe, WPu, and WP1 was 419, 354, 476, 763, 565, 806 mL, respectively. At harvest time, supplied water use efficiencies of DPu and WPu were similar, and reached a peak in both drying and wet treatments. Grain weights per shoot in DPu and WPu were significantly higher than those of other treatments. This implies that phosphorus supplied to the upper soil is beneficial to yield maximum.

Dwarfing genes and cell dimensions in different organs of wheat

A field experiment was conducted under non-limiting water and nutritional conditions with three near-isogenic lines of spring wheat (dwarf, DD; semi-dwarf, SD and standard height, SH) to study the impact of the GA-insensitive alleles Rhtl and Rht2, at the cellular level, on the growth of different vegetative organs and of the pericarp of grains. Cell length and width of blades of different leaves (3, 7 and flag leaf), the flagleaf sheath and the penultimate internode as well as the pericarp of basal grains from central spikelets of the spike were evaluated. With the exception of the flag leaf, dwarfing genes produced a significant reduction in cell length in all the different vegetative organs analysed. There was no effect on the number of cells nor their width. Therefore, in vegetative organs, the effects of these alleles appeared to be exclusively due to a reduction in cell length. It would appear that dwarfing genes act on cell elongation without affecting cell division. The Rht alleles did not modify cell length nor width in the pericarp. Grain weight was different between the lines and these differences were associated with grain volume at the beginning of linear grain growth. Thus, they reduced the size of individual grains by reducing the total number of cells in the pericarp. It appears that Rht alleles reduced the final sizes of vegetative organs (such as internodes and leaves) and of tissues (pericarp) associated with reproductive structures (grains), but the modes of action in these different organs were different.

Dwarfing genes and cell dimensions in different organs of wheat

A field experiment was conducted under non-limiting water and nutritional conditions with three nearisogenic lines of spring wheat (dwarf, DD; semi-dwarf, SD and standard height, SH) to study the impact of the GA-insensitive alleles Rht1 and Rht2, at the cellular level, on the growth of different vegetative organs and of the pericarp of grains. Cell length and width of blades of different leaves (3, 7 and flag leaf), the flagleaf sheath and the penultimate internode as well as the pericarp of basal grains from central spikelets of the spike were evaluated. With the exception of the flag leaf, dwarfing genes produced a significant reduction in cell length in all the different vegetative organs analysed. There was no effect on the number of cells nor their width. Therefore, in vegetative organs, the effects of these alleles appeared to be exclusively due to a reduction in cell length. It would appear that dwarfing genes act on cell elongation without affecting cell division. The Rht alleles did not modify cell length nor width in the pericarp. Grain weight was different between the lines and these differences were associated with grain volume at the beginning of linear grain growth. Thus, they reduced the size of individual grains by reducing the total number of cells in the pericarp. It appears that Rht1 alleles reduced the final sizes of vegetative organs (such as internodes and leaves) and of tissues (pericarp) associated with reproductive structures (grains), but the modes of action in these different organs were different.

Water Status and ABA Content of Floral Organs in Drought-Stressed Wheat

Chemical signals from roots have been shown to mediate the response of vegetative shoots to drought. Our objective was to test whether root signals such as abscisic acid (ABA) affect grain set in wheat. Uniculm wheat was grown in a controlled environment and exposed to a water deficit from pollen mother cell meiosis to late boot stage-a period of reproductive development very sensitive to drought. The water deficit decreased grain numbers per spike up to 70%. As soil moisture was depleted, leaf, glume, ovary and anther water potential (Ψw) decreased with leaf Ψw. Turgor decreased in the leaves, but remained at or above control levels in all floral organs examined. Free ABA content of leaves increased 30-fold as leaf turgor declined, while ABA in floral organs increased 10-15-fold. To separate the effects of shoot and root water status on grain set, plants were pressurised to maintain leaf Ψw at control levels as the soil dried. Pressurisation increased flowers and grains per spike over that of droughted plants at comparable soil water suctions, but not to control levels. Free ABA content in leaves and floral organs increased only about 3-fold when leaves were maintained at high Ψw. Shoot water status had a greater effect on grain set than did soil water status. In both pressurised and unpressurised plants, grains per spike and percentage grain set decreased with increasing ABA content in ovaries and anthers. The results indicate that maintenance of a high shoot water status reduces the effect of soil water deficit on grain set by reducing the accumulation of ABA.

Above-ground vegetative development and growth of winter wheat as influenced by nitrogen and water availability

Assessing the influence of nitrogen and water availability on development and growth of individual organs of winter wheat ( Triticum aestivum L.) is critical in evaluating the response of wheat to environmental conditions. We constructed a simulation model (SHOOTGRO 2.0) of shoot vegetative development and growth from planting to early boot by adding nitrogen and water balances and response functions for seedling emergence, tiller and leaf appearance, leaf and internode growth, and leaf and tiller senescence to the existing wheat development and growth model, SHOOTGRO 1.0. Model inputs include daily maximum and minimum air temperature, rainfall, daily photosynthetically active radiation, soil characteristics necessary to compute soil N and water balances, and several factors describing the cultivar and soil conditions at planting. The model provides information on development and growth characteristics of up to six cohorts of plants within the canopy (cohort groupings are based on time of emergence). The cohort structure allows SHOOTGRO 2.0 to provide output on the frequency of occurrence of plants with specific features (tillers and leaves) within the canopy. The model was constructed so that only water availability limited seedling emergence. Resource availability (nitrogen and water) does not influence time of leaf appearance. Leaf and internode growth, and leaf and tiller senescence processes are limited by the interaction of N and water availability. Tiller appearance is influenced by the interaction of N, radiation and water availability. Predicted and observed dates of emergence and appearance of the first tiller had correlation coefficients of 0.98 and 0.93, respectively. However, these events were, on average, predicted 3.2 and 5.2 days later than observed. SHOOTGRO 2.0 generally under-predicted the number of culms per unit land area, partially because the simulation is limited to a maximum of 16 culms/plant. Model output shows that the simulation is sensitive to N and water inputs. The model provides a tool for predicting vegetative development and growth of the winter wheat with individual culms identified and followed from emergence through boot. SHOOTGRO 2.0 can be used in evaluating alternative crop management strategies.

Comparison of production efficiency of the harvesting organs among field crops

Abstract To investigate the growth efficiency of harvesting organs of rice, winter wheat, oat, barley, maize, sorghum, soybean, field bean, lupin, pea, adzuki bean, chick pea, peanut, sunflower, safflower, flax, rape, castor bean, cotton, and potato, the dry weight and respiratory rate of the harvesting organs were measured and the composition of crude chemical components was determined during maturation. 1. The experimental value of the growth efficiency was generally higher than the theoretical value for biochemical data (Vertregt and Penning de Vries 1987) except for safflower and castor bean.2. The difference between the experimental value and the theoretical value was especially large in soybean, peanut, safflower, rape, and castor bean, in which the lipid content was high, and cotton. Thus, as there was no clear relationship between the composition of the chemical components and the growth efficiency among the crops, it was difficult to estimate the conversion efficiencies for the production of each chemical component using a unit of glucose based on the experimental data. It is, therefore, suggested that reassimilation of respired CO2 or photosynthesis should be included to estimate the carbon balance in the harvesting organs.

Study of phosphorylation of translation elongation factor 2 (EF-2) from wheat germ

Phosphorylation of elongation factor 2 (EF-2) by specific Ca 2+/calmodulin-dependent kinase is considered as a possible mechanism of regulation of protein biosynthesis in animal cells at the level of polypeptide chain elongation. In this report we show that wheat germ EF-2 can be intensively phosphorylated by the rabbit reticulocyte EF-2 kinase. Phosphorylation results in inhibition of the activity of plant EF-2 in poly(U)-dependent cell-free translation system. Thus, the activity of EF-2 in plant cells can be potentially regulated by phosphorylation. However, we could not detect endogenous EF-2 kinase activity in wheat germ either in vitro or in vivo. Furthermore, EF-2 kinase activity is not displayed in different organs of wheat and other higher plants.

Interference by Phosphatases in the Spectrophotometric Assay for Phosphoenolpyruvate Carboxylase

The aim of this work was to discover the extent of interference by phosphoenolpyruvate (PEP) phosphatase in spectrophotometric assays of PEP carboxylase (EC 4.1.1.31) in crude extracts of plant organs. The presence of PEP phosphatase and lactate dehydrogenase (EC 1.1.1.27) in extracts leads to PEP-dependent NADH oxidation that is independent of PEP carboxylase activity, and hence to overestimation of PEP carboxylase activity. In extracts of three organs of pea (Pisum sativum L.: leaves, developing embryos, and Rhizobium nodules), two organs of wheat (Triticum aestivum L.: developing grain and endosperm), and leaves of Moricandia arvensis (L.) D.C., lactate dehydrogenase activity was at most only 16% of that of PEP carboxylase at the pH optimum for PEP carboxylase activity. Endogenous PEP phosphatase and lactate dehydrogenase are thus unlikely to interfere seriously with the assay for PEP carboxylase at its optimum pH. Addition of lactate dehydrogenase to PEP carboxylase assays- a proposed means of correcting for nonenzymic decarboxylation of oxaloacetate to pyruvate-resulted in increases in PEP-dependent NADH oxidation from zero (Rhizobium nodules) to 131% (wheat grains). There was no obvious relationship between the magnitude of this increase and conditions in the assay that might promote oxaloacetate decarboxylation. However, the magnitude of the increase was highly positively correlated with the activity of PEP phosphatase in the extract. Addition of lactate dehydrogenase to PEP carboxylase assays can thus result in very large overestimations of PEP carboxylase activity, and should only be used as a means of correction for oxaloacetate decarboxylation for extracts with negligible PEP phosphatase activity.

Enzyme Activities and Products of CO2 Fixation in Various Photosynthetic Organs of Wheat and Oat

Summary Enzyme activities associated with the Calvin cycle of photosynthesis and with C 4 metabolism, and rates and products of CO 2 fixation were examined with leaves, peduncles, glumes, lemmas, paleae and pericarps of oat and two varieties of wheat («Svenno» from Sweden and «Lerma Rojo» from Mexico). All tissues achieved net CO 2 fixation through the Calvin cycle. Some capacity for C 4 metabolism was detected in the first leaf and, more noticeably, in the tissues surrounding the grain; the latter were also capable of relativelyhigh CO 2 assimilation by phosphoenolpyruvate carboxylase in darkness. Ribulose 1,5-di-phosphate carboxylase activity was greater in leaves, but phosphoenolpyruvate carboxylase activity tended to predominate in the photosynthetic organs of the wheat ear and oat panicle. The wheat pericarp contained pyruvate, Pi dikinase and a relatively high phosphoenolpyruvate carboxylase activity. Glumes, lemmas, paleae and the pericarp seem adapted for catching CO 2 respired by the developing grain in addition to contributing to net CO 2 fixation.

Isozyme variations inAegilops andTriticum. III. Chromosomal basis of the esterase isozyme production in different organs of Chinese spring wheat

Developmental changes of esterase isozymes from the germination to the heading stage of normal and aneuploid lines of common wheat,Triticum aestivum cv. Chinese Spring were studied. A total of twenty major isozymes (Bands 1E to 20E) were observed, some of which were further separated to two to three closely located bands. Among these bands, 1E, 2E, 3E, 5E, 7E, 11E, 14E and 16E were found to be leaf-specific isozymes and 9E, 10E, 13E, 15E, 17E and 18E were seed-specific. Leaf-specific isozyme bands 1E, 2E and 5E are controlled by genes on three homoeologous chromosomes group 6, leaf-specific bands 7E, 11E, 14E and 16E and seed-specific bands 9E, 10E, 13E, 15E, 17E and 18E are under control of genes on homoeologous chromosomes of group 3. On the other hand, two bands, 19′E and 19″E are controlled by genes on chromosomes of homoeologous group 2 in roots of seedlings 10 days old. The present investigation showed that the genes for esterase production located on chromosome 6B had large effects in mature leaves, but chromosomes 6A and 6D had little effect on the esterase isozymes in homoeologous group 6. Genes located on chromosomes 3A, 3B and 3D have a large function in germinating seed; however, chromosomes 3B had little effect on the esterase isozymes in the mature leaf. Present findings confirmed that the chromosomes of the A, B and D genomes have different functions in the production of proteins or enzymes.

Growth kinetics of Marquis wheat. V. Morphogenic dependence

The rate coefficients of the exponential period of growth of the vegetative organs of Marquis wheat were changed and made biphasic by the morphogenesis of the stem apex from the vegetative to the flowering state. The rate coefficient of stem elongation was lower in the initial or vegetative phase than later, and it was initially insensitive to temperature up to 20 °C but temperature sensitive in the final or flowering phase from 10 °C to 30 °C. In contrast the growth coefficients of plant, shoots, and roots computed from measurements of dry weight were higher in the first phase than in the second phase and increased with temperature to a maximum at 20 °C in both phases. The differences were attributed to the less autotrophic nature and initially more limited growth of the stem. The raised stem-growth coefficient in the flowering phase was compensated by slowed growth of its shoot. Tillers grew most rapidly, successive tillers more so, and accounted for the previously observed dominant growth of "stems" as stems plus leaf sheaths. The change of slope within the exponential plots was not noticed in previous work at 25 °C and it portends higher maximal coefficients for vegetative (initial phase) plant growth than those previously estimated from the entire exponential period. However, under optimal conditions the growth coefficient of the whole plant seems to be internally limited to about half that of one or another organ.

Influence of the Various Parts of the Photosynthetic Organs of Wheat and Barley in producing Grains During the Ripening Period. (II)

Experiments were carried out in 1958 on Wheat and barley grown in field and pot culture, to ascertain the amount of contributions, indebted to the activities of several photosynthetic organs as well as to the reserve material contained in them, for the ripening of grains. The amount of contribution was estimated indirectly by the decrease caused by defoliation or shading of the ears, leaves and stems, and measuring the resulted weight of grains and plant parts. The results of both experiments were summarized in table 4. The leaf-blade of wheat contributed about 37 %, the stem with sheath 31 % and the ear itself 21 %, while about 12 % was supplied from reserve materials. In case of barley the leaf blade contributed 27 %, the stem 42 % and the ear 23 %, while 9 % was from the reserve. It was also recongnized that in wheat greater proportion of the total assimilation product of leaves was attributable than in barley. The translocation of reserve material and contribution of ear assimilation showed slight differnce between wheat and barley.