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Sorghum Bicolor (sorghum + bicolor)
Selected AbstractsElevated atmospheric CO2 effects on biomass production and soil carbon in conventional and conservation cropping systemsGLOBAL CHANGE BIOLOGY, Issue 4 2005Stephen A. Prior Abstract Increasing atmospheric CO2 concentration has led to concerns about potential effects on production agriculture as well as agriculture's role in sequestering C. In the fall of 1997, a study was initiated to compare the response of two crop management systems (conventional and conservation) to elevated CO2. The study used a split-plot design replicated three times with two management systems as main plots and two CO2 levels (ambient=375 ,L L,1 and elevated CO2=683 ,L L,1) as split-plots using open-top chambers on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudults). The conventional system was a grain sorghum (Sorghum bicolor (L.) Moench.) and soybean (Glycine max (L.) Merr.) rotation with winter fallow and spring tillage practices. In the conservation system, sorghum and soybean were rotated and three cover crops were used (crimson clover (Trifolium incarnatum L.), sunn hemp (Crotalaria juncea L.), and wheat (Triticum aestivum L.)) under no-tillage practices. The effect of management on soil C and biomass responses over two cropping cycles (4 years) were evaluated. In the conservation system, cover crop residue (clover, sunn hemp, and wheat) was increased by elevated CO2, but CO2 effects on weed residue were variable in the conventional system. Elevated CO2 had a greater effect on increasing soybean residue as compared with sorghum, and grain yield increases were greater for soybean followed by wheat and sorghum. Differences in sorghum and soybean residue production within the different management systems were small and variable. Cumulative residue inputs were increased by elevated CO2 and conservation management. Greater inputs resulted in a substantial increase in soil C concentration at the 0,5 cm depth increment in the conservation system under CO2 -enriched conditions. Smaller shifts in soil C were noted at greater depths (5,10 and 15,30 cm) because of management or CO2 level. Results suggest that with conservation management in an elevated CO2 environment, greater residue amounts could increase soil C storage as well as increase ground cover. [source] Above- and below-ground responses of C3,C4 species mixtures to elevated CO2 and soil water availabilityGLOBAL CHANGE BIOLOGY, Issue 3 2003JUSTIN D. DERNER Abstract We evaluated the influences of CO2[Control, , 370 µmol mol,1; 200 µmol mol,1 above ambient applied by free-air CO2 enrichment (FACE)] and soil water (Wet, Dry) on above- and below-ground responses of C3 (cotton, Gossypium hirsutum) and C4 (sorghum, Sorghum bicolor) plants in monocultures and two density mixtures. In monocultures, CO2 enrichment increased height, leaf area, above-ground biomass and reproductive output of cotton, but not sorghum, and was independent of soil water treatment. In mixtures, cotton, but not sorghum, above-ground biomass and height were generally reduced compared to monocultures, across both CO2 and soil water treatments. Density did not affect individual plant responses of either cotton or sorghum across the other treatments. Total (cotton + sorghum) leaf area and above-ground biomass in low-density mixtures were similar between CO2 treatments, but increased by 17,21% with FACE in high-density mixtures, due to a 121% enhancement of cotton leaf area and a 276% increase in biomass under the FACE treatment. Total root biomass in the upper 1.2 m of the soil was not influenced by CO2 or by soil water in monoculture or mixtures; however, under dry conditions we observed significantly more roots at lower soil depths (> 45 cm). Sorghum roots comprised 81,85% of the total roots in the low-density mixture and 58,73% in the high-density mixture. CO2 -enrichment partly offset negative effects of interspecific competition on cotton in both low- and high-density mixtures by increasing above-ground biomass, with a greater relative increase in the high-density mixture. As a consequence, CO2 -enrichment increased total above-ground yield of the mixture at high density. Individual plant responses to CO2 enrichment in global change models that evaluate mixed plant communities should be adjusted to incorporate feedbacks for interspecific competition. Future field studies in natural ecosystems should address the role that a CO2 -mediated increase in C3 growth may have on subsequent vegetation change. [source] Elevated carbon dioxide and irrigation effects on water stable aggregates in a Sorghum field: a possible role for arbuscular mycorrhizal fungiGLOBAL CHANGE BIOLOGY, Issue 3 2001Matthias C. Rillig Summary While soil biota and processes are becoming increasingly appreciated as important parameters for consideration in global change studies, the fundamental characteristic of soil structure is a neglected area of research. In a sorghum [Sorghum bicolor (L.) Moench] field experiment in which CO2[supplied using free-air CO2 enrichment (FACE) technology] was crossed factorially with an irrigation treatment, soil aggregate (1,2 mm) water stability increased in response to elevated CO2. Aggregate water stability was increased by 40% and 20% in response to CO2, at ample and limited water supply treatments, respectively. Soil hyphal lengths of arbuscular mycorrhizal fungi (AMF) increased strongly (with a threefold increase in the dry treatment) in response to CO2, and the concentrations of one fraction (easily extractable glomalin, EEG) of the AMF-produced protein glomalin were also increased. Two fractions of glomalin, and AMF hyphal lengths were all positively correlated with soil aggregate water stability. The present results further support the hypothesis that AMF can become important in global change scenarios. Although in this field study a causal relationship between hyphal length, glomalin and aggregate stability cannot be demonstrated, the present data do suggest that AMF could mediate changes in soil structure under elevated CO2. This could be of great importance in agricultural systems threatened by erosional soil loss. [source] Effect of malt pretreatment on phytate and tannin level of two sorghum (Sorghum bicolor) cultivarsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 10 2006Wisal H. Idris Summary The seeds of two cultivars of Sudanese sorghum (Sorghum bicolor), namely Wad Ahmed and Tabat, were germinated for 4 days to obtain 1-, 2- and 4-day-old malts. Sorghum malt (5% and 10%) was added to sorghum flour. The mixtures were incubated at 30 °C with shaking for 30, 60, 90 and 120 min. Malting loss was very slight for both cultivars and for all incubation periods. Phytic acid and tannin contents were assayed for all treatments. The results revealed that phytate and tannin contents were significantly (P , 0.05) reduced when sorghum flour was pretreated with malt. When a mixture containing 10%, 4-day-old malt and sorghum flour was incubated for 120 min, it significantly (P , 0.05) reduced phytate and tannin contents by 92% and 98%, respectively, for Wad Ahmed cultivar, while for Tabat they were reduced by 93% and 96%, respectively. The rate of reduction of phytate and tannin content increased with incubation time and malt age and concentration. [source] Effect of Drought Stress on Yield and Quality of Maize/Sunflower and Maize/Sorghum Intercrops for Biogas ProductionJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 4 2010S. SchittenhelmArticle first published online: 16 FEB 2010 Abstract Intercropping represents an alternative to maize (Zea mays L.) monoculture to provide substrate for agricultural biogas production. Maize was intercropped with either sunflower (Helianthus annuus L.) or forage sorghum [Sorghum bicolor (L.) Moench] to determine the effect of seasonal water supply on yield and quality of the above-ground biomass as a fermentation substrate. The two intercrop partners were grown in alternating double rows at plant available soil water levels of 60,80 %, 40,50 % and 15,30 % under a foil tunnel during the years 2006 and 2007 at Braunschweig, Germany. Although the intercrop dry matter yields in each year increased with increasing soil moisture, the partner crops responded quite differently. While maize produced significantly greater biomass under high rather than low water supply in each year, forage sorghum exhibited a significant yield response only in 2006, and sunflower in none of the 2 years. Despite greatly different soil moisture contents, the contribution of sorghum to the intercrop dry matter yield was similar, averaging 43 % in 2006 and 40 % in 2007. Under conditions of moderate and no drought stress, sunflower had a dry matter yield proportion of roughly one-third in both years. In the severe drought treatment, however, sunflower contributed 37 % in 2006 and 54 % in 2007 to the total intercrop dry matter yield. The comparatively good performance of sunflower under conditions of low water supply is attributable to a fast early growth, which allows this crop to exploit the residual winter soil moisture. While the calculated methane-producing potential of the maize/sorghum intercrop was not affected by the level of water supply, the maize/sunflower intercrop in 2006 had a higher theoretically attainable specific methane yield under low and medium than under high water supply. Nevertheless, the effect of water regime on substrate composition within the intercrops was small in comparison with the large differences between the intercrops. [source] Nitrogen, Phosphorus, Potassium, Magnesium and Calcium Removal by Brown Midrib Sorghum Sudangrass in the Northeastern USAJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 6 2006Q. M. Ketterings Abstract For the long-term sustainability of the dairy industry in the Northeastern USA, manure nutrient application rates should not exceed crop nutrient removal once above-optimum soil fertility levels are reached. Dairy producers have shown a growing interest in brown midrib (BMR) forage sorghum (Sorghum bicolor (L.) Moench.) × sudangrass (Sorghum sudanense Piper) hybrids (S × S) as a more environmentally sound alternative to maize (Zea mays L.) but data on S × S nutrient removal rates are scant. Our objectives were to determine N, P, K, Ca and Mg removal with harvest as impacted by N application rate, using six N rate studies in New York. One of the six sites had a recent manure history. Although site-to-site differences existed, N application tended to decrease P and K and increase N, Ca and Mg concentrations in BMR S × S forage. Nutrient removal and yield were highly correlated for all sites except one location that showed a K deficiency. The crop removed large amounts of P and K in the manured site, suggesting that BMR S × S is an excellent scavenger of these nutrients. If manure is applied mid-season, forage K levels are likely too high for feeding to non-lactating cows. [source] Effect of Nitrogen Rate and Stubble Height on Dry Matter Yield, Crude Protein Content and Crude Protein Yield of a Sorghum,Sudangrass Hybrid[Sorghum bicolor (L.) Moench × Sorghum sudanense (Piper) Stapf.] in the Three-Cutting SystemJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 4 2003S. Iptas Abstract In this study, the effects of nitrogen (N) rate (60, 120, 180 and 240 kg N ha,1 applied in three equal dressings at seeding and after the first and second cuttings) and stubble height (7, 14 and 21 cm) on the dry matter (DM) yield, crude protein (CP) content, and CP yield of a sorghum,sudangrass hybrid [Sorghum bicolor (L.) Moench × Sorghum sudanense (Piper) Stapf., cv. Pioneer 988] in the three-cut system was investigated. The N rate had no significant effect in the first and third cuttings, but in the second cutting DM yields increased significantly with increase in N rate. The highest yield of 9.1 t ha,1 was obtained with 80 kg N ha,1 for the average of 2 years at the second cutting, but no significant difference was found among the 40, 60 and 80 kg N ha,1 rates. CP content and yield were not significantly affected by N rate at the first and third cuttings, but CP content and yield were significantly affected by application of N at the second cutting. Stubble height had a significant effect on CP content at the third cutting. However, it had no significant effect on CP content at the first and second cuttings. Stubble height had a significant effect on the CP yield at the first cutting, but no significant effect on CP yield at the second and third cuttings. [source] Host-plant preference and oviposition responses of the sorghum midge, Stenodiplosis sorghicola (Coquillett) (Dipt., Cecidomyiidae) towards wild relatives of sorghumJOURNAL OF APPLIED ENTOMOLOGY, Issue 3 2001Sharma Sorghum midge, Stenodiplosis (Contarinia) sorghicola (Coquillett) is an important pest of grain sorghum world-wide. Considerable progress has been made in screening and breeding for resistance to sorghum midge. However, some of the sources of resistance have become susceptible to sorghum midge in Kenya, in eastern Africa. Therefore, the wild relatives of Sorghum bicolor were studied as a possible source of new genes conferring resistance to sorghum midge. Midge females did not lay eggs in the spikelets of Sorghum amplum, Sorghum bulbosum, and Sorghum angustum compared to 30% spikelets with eggs in Sorghum halepense when infested with five midge females per panicle under no-choice conditions. However, one egg was laid in S. amplum when infested with 50 midges per panicle. A larger number of midges were attracted to the odours from the panicles of S. halepense than to the panicles of Sorghum stipoideum, Sorghum brachypodum, S.angustum, Sorghum macrospermum, Sorghum nitidium, Sorghum laxiflorum, and S. amplum in dual-choice olfactometer tests. The differences in midge response to the odours from S. halepense and Sorghum intrans were not significant. Under multi-choice conditions, when the females were also allowed a contact with the host, more sorghum midge females were attracted to the panicles of S. bicolor compared with S. amplum, S. angustum, and S. halepense. In another test, numerically more midges responded to the panicles of IS 10712 compared with S. halepense, whereas the differences in midge response to the panicles of ICSV 197 (S. bicolor) and S. halepense were not apparent, indicating that S. halepense is as attractive to sorghum midge females as S. bicolor. The wild relatives of sorghum (except S. halepense) were not preferred for oviposition, and they were also less attractive to the sorghum midge females. Thus, wild relatives of sorghum can prove to be an alternative source of genes for resistance to sorghum midge. [source] Biodegradation of disperse textile dye Brown 3REL by newly isolated Bacillus sp.JOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2008Abstract Aims:, To isolate the potential micro-organism for the degradation of textile disperse dye Brown 3 REL and to find out the reaction mechanism. Methods and Results:, 16S rDNA analysis revealed an isolate from textile effluent contaminated soil as Bacillus sp. VUS and was able to degrade (100%) dye Brown 3REL within 8 h at static anoxic condition. A significant increase in the activities of lignin peroxidase, laccase and NADH-DCIP reductase was observed up to complete decolourization of Brown 3REL. The optimum temperature required for degradation was 40°C and pH 6·5,12·0. Phyto-toxicity and chemical oxygen demand revealed nontoxic products of dye degradation. The biodegradation was monitored by UV,VIS, FTIR spectroscopy and HPLC. The final products 6,8-dichloro-quinazoline-4-ol and cyclopentanone were characterized by gas chromatography-mass spectrometry. This Bacillus sp. VUS also decolourized (80%) textile dye effluent within 12 h. Conclusions:, This study suggests that Bacillus sp. VUS could be a useful tool for textile effluent treatment. Significance and Impact of the Study:, The newly isolated Bacillus sp. VUS decolourized 16 textile dyes and textile dye effluent also. It achieved complete biodegradation of Brown 3REL. Phytotoxicity study demonstrated no toxicity of the biodegraded products for plants with respect to Triticum aestivum and Sorghum bicolor. [source] Reservoir and Non-reservoir Hosts of Bean-Wilt Pathogen, Fusarium oxysporum f. sp. phaseoliJOURNAL OF PHYTOPATHOLOGY, Issue 7-8 2001O. D. Dhingra Abstract The capacity of Fusarium oxysporum f. sp. phaseoli to multiply in the roots of 12 non-host plant species was determined with the objective of selecting potential candidates for crop rotation and/or green manuring in infested bean fields. The plants were inoculated at the seedling stage by a benomyl-resistant mutant of the pathogen using the root-dip technique and transplanted to natural soil. The number of colony forming units/g dry root tissue (CFU/g) was determined at the full bloom stage. Quantitatively, the root colonization differed greatly among the plant species. The roots and lower stem of Dolichos lablab, Phaseolus lunatus, Mucuna aterrima, Canavalia ensiforme and Vigna unguiculata were the most compatible with the pathogen and those of Sorghum bicolor, Crotalaria juncea, Oryza sativa and Zea mays were least compatible. No disease symptoms developed on any plant species. Chlamydospore germination in the rhizosphere also differed significantly among the plant species. There was no correlation between percentage chlamydospore germination in the rhizosphere and extent of root colonization. Most plant species recommended for green manuring in bean fields allowed extensive root and stem colonization by F. o. f. sp. phaseoli and were considered as reservoir hosts. All three of the gramineous species tested and C. juncea were classed as non-reservoir host, because the pathogen did not colonize the stem and its multiplication in the roots was very low. These plant species appear to be good candidates for long-term field evaluation to determine their usefulness in an integrated management of Fusarium bean-wilt. [source] Phosphate buffer,extractable organic nitrogen as an index of soil-N availability for sorghum and pearl milletJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 2 2010Asako Mori Abstract The availability of soil nitrogen (N) is usually quantified by the amount of mineralized N as determined after several weeks of soil incubation. Various alternative methods using chemical solvents have been developed to extract the available organic N, which is easily mineralized. We compared one such solution, neutral phosphate buffer (NPB), with conventional incubation and 0.01 M,CaCl2 extraction, as measures of soil N available to two major cereal crops of the semiarid tropics, based on the total N uptake by plants in a pot experiment. Mineralized N had the highest correlation with N uptake by pearl millet (Pennisetum glaucum L., r = 0.979***) and sorghum (Sorghum bicolor [L.] Moench, r = 0.978***). NPB-extractable N was also highly correlated with N uptake (pearl millet, r = 0.876***; sorghum, r = 0.872***). Only one major peak was detected when NPB extracts were analyzed using size-exclusion high-performance liquid chromatography, regardless of soil properties. In addition, the organic N extracted with NPB was characterized by determining the content of peptidoglycan, the main component of bacterial cell walls. Although the characteristics of NPB-extractable organic N are still unclear, it offers a promising quick assay of available N. [source] CONTROLLING PHOSPHORUS IN RUNOFF FROM LONG TERM DAIRY WASTE APPLICATION FIELDS,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 5 2004Anne M.S. McFarland ABSTRACT: Phosphorus (P) in runoff from long term animal waste application fields can contribute to accelerated eutrophication of surface waters. Manure when applied at nitrogen (N) agronomic rates generally increases soil P concentrations, which can increase runoff of soluble P. Along the North Bosque River in central Texas, dairy waste application fields are identified as the most controllable nonpoint source of soluble P in a total maximum daily load. To evaluate P reduction practices for fields high in soil extractable P, edge-of-field runoff was measured from paired plots of Coastal bermudagrass (Cynodon dactylon) and sorghum (Sorghum bicolor)/ winter wheat (Triticum spp.). Plots (about 0.4 ha) received manure at P agronomic rates following Texas permit guidelines and commercial N during the pretreatment period. During the post-treatment period, control plots continued to receive manure at P agronomic rates and commercial N. Treatment plots received only commercial N during the post-treatment period. Use of only commercial N on soils with high extractable P levels significantly decreased P loadings in edge-of-field runoff by at least 40 percent, but runoff concentrations sometimes increased. No notable changes in extractable soil P concentrations were observed after five years of monitoring due to drought conditions limiting forage uptake and removal. [source] Fodder production and soil health with conjunctive use of saline and good quality water in ustipsamments of a semi-arid regionLAND DEGRADATION AND DEVELOPMENT, Issue 2 2007R. K. Yadav Abstract Food and fodder shortage in arid and semi-arid regions force farmers to use marginal quality water for meeting the water requirement of crops which result in low quality, reduced production and an adverse impact on soil properties. A field study on loamy-sand (Hyperthermic Typic Ustipsamments) saline soil was conducted during 1999,2001 at Central Institute for Research on Buffaloes, Hisar. This involved assessment of effects of conjunctive use of saline water, EC,=,4·6,7·4,dSm,1, SAR,=,14,22 ((mmol,1)˝ with good quality water on five fodder crop rotations: oat-sorghum (Avena sativa- ,Sorghum bicolor), rye grass,sorghum (Loleum rigidum,Sorghum bicolor), Egyptian clover,sorghum (Trifoleum alexandrinum,Sorghum bicolor), Persian clover,sorghum (Trifoleum resupinatum,Sorghum bicolor) and Indian clover,sorghum (Melilotus indica,Sorghum bicolor) and certain soil properties associated with it. Leguminous winter fodder crops were more sensitive to poor quality water use. Reductions in fodder yield with use of saline water alone throughout season were 85, 68, 54, 42, 36 and 26 per,cent in Indian clover, Egyptian clover, Persian clover, oat, rye grass and sorghum respectively as compared to good quality water. Leguminous fodder crops produced protein rich (12,14 per,cent) and low fibre (18,20 per,cent) fodder as compared to poor quality grassy fodder under good quality water irrigation but their quality deteriorated when saline water was used. These leguminous crops accumulated proportionately higher Na+ (1·58 per,cent) resulting in adverse impact on their growth as compared to grassy fodder crops. Higher soil salinity (12·2,dSm,1), SAR,=,20 (mmol,1)˝ was recorded with saline water irrigation; and slight adverse impact was noticed on infiltration rate and contents of water dispersible clay. Alternate cyclic use of canal and saline water could be an option for fodder production under such conditions. Copyright © 2006 John Wiley & Sons, Ltd. [source] Silicification in sorghum (Sorghum bicolor) cultivars with different drought tolerancePHYSIOLOGIA PLANTARUM, Issue 1 2002Alexander Lux Sorghum belongs to a group of economically important, silicon accumulating plants. X-ray microanalysis coupled with environmental scanning electron microscopy (ESEM) of fresh root endodermal and leaf epidermal samples confirms histological and cultivar specificity of silicification. In sorghum roots, silicon is accumulated mostly in endodermal cells. Specialized silica aggregates are formed predominantly in a single row in the form of wall outgrowths on the inner tangential endodermal walls. The density of silica aggregates per square mm of inner tangential endodermal cell wall is around 2700 and there is no significant difference in the cultivars with different content of silicon in roots. In the leaf epidermis, silicon deposits were present in the outer walls of all cells, with the highest concentration in specialized idioblasts termed ,silica cells'. These cells are dumb-bell shaped in sorghum. In both the root endodermis and leaf epidermis, silicification was higher in a drought tolerant cultivar Gadambalia compared with drought sensitive cultivar Tabat. Silicon content per dry mass was higher in leaves than in roots in both cultivars. The values for cv. Gadambalia in roots and leaves are 3.5 and 4.1% Si, respectively, and for cv. Tabat 2.2 and 3.3%. However, based on X-ray microanalysis the amount of Si deposited in endodermal cell walls in drought tolerant cultivar (unlike the drought susceptible cultivar) is higher than that deposited in the leaf epidermis. The high root endodermal silicification might be related to a higher drought resistance. [source] Brassinosteroids as Metahormones: Evidence for their Specific Influence during the Critical Period in Sorghum DevelopmentPLANT BIOLOGY, Issue 6 2002G. N. Amzallag Abstract: In Sorghum bicolor, the effect of brassinosteroid (BR) treatments on blade elongation depends both on concentration and on the stage of development. A specific period of increase in sensitivity to BR is reported during early vegetative development. It coincides with emergence of a critical period during which the between-organs relationship is readjusted as a function of new developmental events or new environmental conditions. Accordingly, the influence of BR cannot be completely understood without separating its effects during stable phases (phenophases) and during critical periods. A high level of redundancy exists in networks of regulation, so that modifications due to BR treatments generally remain cryptic. Nevertheless, it is shown that BR affects the pattern of relationships between organs, confirming its involvement in emergence of a new network of regulation. It is suggested that, during critical periods, brassinosteroids act as "metahormones" integrating the new emerging regulation network by triggering changes in cellular sensitivity to PGRs. [source] Developmental Changes in Effect of Cytokinin and Gibberellin on Shoot K+ and Na+ Accumulation in Salt-Treated Sorghum PlantsPLANT BIOLOGY, Issue 4 2001G. N. Amzallag Abstract: The effect of cytokinin (CK) and/or gibberellin (GA) treatments on shoot accumulation of Na+ and K+ was investigated in Sorghum bicolor exposed to 150 mM NaCl. These hormonal treatments modified the shoot content of Na+ and K+, but the effect varied throughout development. Comparison of ion concentration versus ion content in shoots indicates that regulation of shoot concentration of K+ is modified during a transition period of development. This change is concomitant with reorganization of the regulation network for meristem activity, an event also involving changes in sensitivity to CK and GA. This evidence suggests a strong interdependency between dynamic changes in a between-organ network of relations and control of accumulation of monovalent ions in the shoot. Moreover, a new pattern of regulation of shoot Na+ concentration emerges during the transition period. During this process GA appears progressively involved in regulation of Na retranslocation, while CK is rather controlling the root uptake of Na+. Accordingly, the spontaneous emergence of Na-includer and Na-excluder individuals observed from an initially homogeneous population is interpreted as related to variations in sensitivity to GA and CK during differentiation of this newly emerging pathway of regulation. [source] Data analysis in plant physiology: are we missing the reality?PLANT CELL & ENVIRONMENT, Issue 9 2001G. N. Amzallag Abstract In plant physiology, data analysis is based on the comparison of mean values. In this perspective, variability around the mean value has no significance per se, but only for estimating statistical significance of the difference between two mean values. Another approach to variability is proposed here, derived from the difference between redundant and deterministic patterns of regulation in their capacity to buffer noise. From this point of view, analysis of variability enables the investigation of the level of redundancy of a regulation pattern, and even allows us to study its modifications. As an example, this method is used to investigate the effect of brassinosteroids (BSs) during vegetative growth in Sorghum bicolor. It is shown that, at physiological concentrations, BSs modulate the network of regulation without affecting the mean value. Thus, it is concluded that the physiological effect of BSs cannot be revealed by comparison of mean values. This example illustrates how a part of the reality (in this case, the most relevant one) is hidden by the classical methods of comparison between mean values. The proposed tools of analysis open new perspectives in understanding plant development and the non-linear processes involved in its regulation. They also ask for a redefinition of fundamental concepts in physiology, such as growth regulator, optimality, stress and adaptation. [source] Naturally low carbonic anhydrase activity in C4 and C3 plants limits discrimination against C18OO during photosynthesisPLANT CELL & ENVIRONMENT, Issue 9 2000J. S. Gillon ABSTRACT The 18O content of CO2 is a powerful tracer of photosynthetic activity at the ecosystem and global scale. Due to oxygen exchange between CO2 and 18O-enriched leaf water and retrodiffusion of most of this CO2 back to the atmosphere, leaves effectively discriminate against 18O during photosynthesis. Discrimination against 18O (,18O) is expected to be lower in C4 plants because of low ci and hence low retrodiffusing CO2 flux. C4 plants also generally show lower levels of carbonic anhydrase (CA) activities than C3 plants. Low CA may limit the extent of 18O exchange and further reduce ,18O. We investigated CO2,H2O isotopic equilibrium in plants with naturally low CA activity, including two C4 (Zea mays, Sorghum bicolor) and one C3 (Phragmites australis) species. The results confirmed experimentally the occurrence of low ,18O in C4, as well as in some C3, plants. Variations in CA activity and in the extent of CO2,H2O isotopic equilibrium (,eq) estimated from on-line measurements of ,18O showed large range of 0,100% isotopic equilibrium (,eq= 0,1). This was consistent with direct estimates based on assays of CA activity and measurements of CO2 concentrations and residence times in the leaves. The results demonstrate the potential usefulness of ,18O as indicator of CA activity in vivo. Sensitivity tests indicated also that the impact of ,eq< 1 (incomplete isotopic equilibrium) on 18O of atmospheric CO2 can be similar for C3 and C4 plants and in both cases it increases with natural enrichment of 18O in leaf water. [source] DNA sequence variation in the ITS-1 rDNA subunit and host relationships in sorghum midge, Stenodiplosis sorghicola (Coquillett) (Diptera: Cecidomyiidae), in AustraliaAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 2 2002Bradley C Congdon Abstract Sequence variation in the internal transcribed spacer (ITS-1) ribosomal DNA subunit was examined for sorghum midge obtained from introduced and native hosts in south-eastern and central Queensland. No variation was observed relative to host plant or geographical distance for midges collected from two introduced hosts, grain sorghum (Sorghum bicolor) and Johnson grass (S. halepense); however, sequence differences were observed between midges from introduced and native hosts and among midges from a single native host, slender bluegrass (Dichanthium affine). No evidence was observed of introduced midges on native hosts, or vice versa. These results agree with previously hypothesised host distributions for native and introduced midges in Australia, and expand the sample of introduced hosts to include Johnson grass. They suggest that Stenodiplosis sorghicola, the principal midge infesting grain sorghum, is also the most common species on Johnson grass. This confirms that Johnson grass plays a role in the population dynamics of S. sorghicola and suggests that midges originating from Johnson grass may influence levels of infestation in grain sorghum. [source] | |||||||||||||||||||||||||