Amount Of Non-structural Carbohydrates Research Articles

Evaluation of Grain-Filling-Related Traits Using Taichung 65 x DV85 Chromosome Segment Substitution Lines (TD-CSSLs) of Rice.

Grain yield of rice consists of sink capacity and grain filling. There are some genes known to contribute to sink capacity, but few genes associated with grain filling are known. We conducted a genetic analysis on yield-related traits by using a chromosome segment substitution line population that have introgression from DV85, an aus variety of rice, in the background of T65, a japonica variety. Refined whole-genome genotypes of the 43 TD-CSSLs were obtained by genotyping-by-sequencing. The effects of previously detected quantitative trait loci (QTLs), qNSC1 and qNSC2, were confirmed by the amount of non-structural carbohydrate (NSC) at 5 days after heading (DAH). The CSSL for qSWTR11, the QTL for decrease in shoot weight during the maturity stage, showed the highest NSC at 5 DAH and lowest at 35 DAH. The brown rice yield of these lines were not stably significant. Most of the sink-related traits correlated between the 2 tested years, but most of the grain-filling traits did not show correlation between the 2 years. Correlation analysis revealed that the sink capacity is stable and primarily determines the yield, and grain filling is more affected by the environment. In addition, biomass production before heading and during the maturity stage contributes to higher yield in TD-CSSLs, and the amount of translocation of stem reserve does not affect much to the yield. We conclude that higher NSC at the heading stage and rapid decrease in shoot biomass during the maturity stage did not directly contribute to the yield formation in the japonica genetic background.

Amplifying feedback loop between growth and wood anatomical characteristics of Fraxinus excelsior explains size-related susceptibility to ash dieback.

Since the 1990s the invasive fungus Hymenoscyphus fraxineus has caused severe crown dieback and high mortality rates in Fraxinus excelsior in Europe. In addition to a strong genetic control of tolerance to the fungus, previous studies have found landscape heterogeneity to be an additional driver of variability in the severity of dieback symptoms. However, apart from climatic conditions related to heat and humidity influencing fungal infection success, the mechanistic understanding of why smaller or slower-growing trees are more susceptible to dieback remains less well understood. Here, we analyzed three stands in Switzerland with a unique setting of 8years of data availability of intra-annual diameter growth and annual crown health assessments. We complemented this by ring width and quantitative wood anatomical measurements extending back before the monitoring started to investigate if wood anatomical adjustments can help better explain the size-related dieback phenomenon. We found that slower-growing trees or trees with smaller crowns already before the arrival of the fungus were more susceptible to dieback and mortality. Defoliation directly reduced growth as well as maximum earlywood vessel size, and the positive relationship between vessel size and growth rate caused a positive feedback amplifying and accelerating crown dieback. Measured non-structural carbohydrate (NSC) concentrations in the outermost five rings did not significantly vary between healthy and weakened trees, which translate into large differences in absolute available amount of NSCs. Thus, we hypothesize that a lack of NSCs (mainly sugars) leads to lower turgor pressure and smaller earlywood vessels in the following year. This might impede efficient water transport and photosynthesis, and be responsible for stronger symptoms of dieback and higher mortality rates in smaller and slower-growing trees.

Role of brassinosteroids in rice spikelet differentiation and degeneration under soil-drying during panicle development

BackgroundBrassinosteroids (BRs) are a new group of plant hormones and play important roles in plant growth and development. However, little information is available if BRs could regulate spikelet development in rice (Oryza sativa L.) especially under soil-drying conditions. This study investigated whether and how BRs mediate the effect of soil-drying on spikelet differentiation and degeneration in rice. A rice cultivar was field-grown and exposed to three soil moisture treatments during panicle development, that is, well-watered (WW), moderate soil-drying (MD) and severe soil-drying (SD).ResultsCompared with the WW treatment, the MD treatment enhanced BRs biosynthesis in young panicles, increased spikelet differentiation and reduced spikelet degeneration. The SD treatment had the opposite effects. Changes in expression levels of key rice inflorescence development genes (OsAPO2 and OsTAW1), ascorbic acid (AsA) content, and activities of enzymes involved AsA synthesis and recycle, and amount of nonstructural carbohydrates (NSC) in young panicles were consistent with those in BRs levels, whereas hydrogen peroxide (H2O2) content showed opposite trend. Knockdown of the BRs synthesis gene OsD11 or application of a BRs biosynthesis inhibitor to young panicles markedly decreased OsAPO2 and OsTAW1 expression levels, BRs and AsA contents, activities of enzymes involved AsA synthesis and recycle, NSC amount in rice panicles and spikelet differentiation but increased the H2O2 content and spikelet degeneration compared to the control (the wide type or application of water). The opposite effects were observed when exogenous BRs were applied.ConclusionsThe results suggest that BRs mediate the effect of soil-drying on spikelet differentiation and degeneration, and elevated BRs levels in rice panicles promote spikelet development under MD by enhancing inflorescence meristem activity, AsA recycle and NSC partitioning to the growing panicles.

Depositing ability of stem of winter wheat varieties of different periods of selection

Adaptation of high-yielding winter wheat crops to changes in climatic conditions has great importance for food security of countries. The remobilization of stem assimilates for grain filling is one of the possible ways of increasing wheat yield in unfavourable environmental conditions. Field experiments in natural conditions with three old and three modern varieties of winter wheat were performed to compare depositing abilities of their stems. The objective of this study was a comparative analysis of the parameters of depositing capacity of stems of the main shoots for identification of the criteria for assessing grain productivity of winter wheat. The parameters of depositing capacity of the stem of the main shoots of three old winter wheat varieties (1997, 2003, and 2008) and three modern ones (2013, 2014 and 2016) were studied in field conditions with natural conditions of water supply (Kyiv Oblast, Ukraine). During the period of formation of reproductive organs (April and May), the amount of precipitation, respectively, was only 17% and 68% of long-term values and average monthly air temperature was 3–4 ºС higher than the climatic norm. We analyzed the variability of the parameters of depositing capacity of the stem of the main shoot and grain productivity of the ear of six wheat winter varieties which differed by time of selection. In unfavourable conditions during the period of formation of reproductive organs the modern winter wheat varieties had an 11% higher yield on average compared to the older ones. It was determined that the highest mass of grain from the ear of the main shoots (1.9–2.1 g) belonged to Odeska 267 variety, a drought-tolerant variety from earlier selection, and three modern varieties – Raihorodka, Prydniprovska and Darunok Podillia. It is demonstrated that these varieties also exceeded two old varieties (Podolianka and Yednist) by stem dry matter weight of main shoot at anthesis by 0.3–0.6 g. The highest content of non-structural carbohydrates at this phase was observed in Odeska 267, Raihorodka and Darunok Podillia varieties (273–307 mg/stem). Correlation analysis revealed the significant correlation between mass of grain from ear and dry matter of stem at anthesis and full ripeness, as well mass of grain from ear and the amount of non-structural carbohydrates at anthesis. Therefore, modern varieties of winter wheat and the drought-tolerant variety have higher yield, weight of dry matter of stem of the main shoot at anthesis and grain productivity of the ear, compared to old varieties. The results of this study indicate that the mass of dry matter of the stem of the main shoot at anthesis can be used as a marker of the grain productivity of winter wheat.

Assaying Sorghum for Fuel Production.

The publicly available NREL suite of laboratory analytical procedures (LAPs) provides researchers with the analytical tools to determine the composition of woody and herbaceous feedstocks. Feedstock characterization includes several steps: sample preparation, starch determination, moisture analysis, ashing, extraction, and hydrolysis. These steps provide information on specific compounds and classes of compounds such as ash, protein, moisture, extractives, sucrose, starch, glucan, xylan, galactan, arabinan, acetate and lignin. Here, we describe the use of these procedures to characterize sorghum [Sorghum bicolor (L.) Moench] with specific consideration of four main sorghum types: grain, forage, sweet, and biomass, which can vary significantly in composition. Special attention is paid to the extraction and the differentiation of glucose from starch and glucan from cellulose in the hybrids with significant amounts of nonstructural carbohydrates.

Chemical composition and yield of rhizome biomass of Arundo donax L. grown for biorefinery in the Mediterranean environment

The contribution of the rhizome to productivity of fermentable sugars and the detailed composition of rhizomes were analyzed in three mature stands of Arundo donax L. cultivated in three locations of variable fertility in the South of Italy. Although the average yearly aboveground dry biomass and rhizome amount showed large and significant differences among sites, (15.3 and 2.6 Mg ha−1 year−1 of rhizomes in the most and less productive sites respectively), rhizomes of all sites had more than 30% of the dry matter (DM) as non-structural carbohydrates (NSC). Sucrose and starch were the most abundant NSC but measurable amounts of glucose, fructose, galactose and of the valuable trisaccharide raffinose were also present. The amount of NSC in rhizomes affected their content of dry mater, and water extractives. The ash content also varied significantly among cultivation sites; the highest amount was recorded in rhizomes of the most productive site (Acerra). The abundance in cell wall components of rhizomes was similar to that of published values for the above ground biomass. The present results demonstrate that NSC content in rhizomes of mature stands is a conserved trait. Hence, rhizome biomass, thanks to its quantity and high fermentable sugars content, should be considered as a relevant fraction of the A. donax crop product whose utilization can increase the productivity and the environmental fingerprint of this crop, in view of its biomass utilization in biorefinery.

Patterns in non-structural carbohydrate and nitrogen reserves in chicory (Cichorium intybus L.) and plantain (Plantago lanceolata L.) during regrowth in summer

Chicory (Cichorium intybus L.) and narrow-leaved plantain (Plantago lanceolata L.) are capable of producing a large amount of high quality feed during summer. Like many species, grazing management decisions influence their dry matter (DM) production. One of the factors implicated in the grazing-management effect on yield of other forages are plant non-structural carbohydrate (NSC) or nitrogen (N) reserves. The aim of this experiment was to characterise the patterns of NSC and N reserve depletion and replenishment for chicory and plantain during a 35-day regrowth cycle in summer, and investigate the impact of residual height on NSC and N reserves. In chicory roots, the NSC concentration tended (P = 0.09) to decline for 7 days post-defoliation before replenishment began and pre-defoliation concentrations were attained by Day 21 of regrowth (310 growing degree-days; GDD). Similarly, the amount of NSC in plantain roots declined for 14 days post-defoliation (P < 0.001), increasing again from Day 21 and with full replenishment to pre-defoliation levels by Day 35 of regrowth (532 GDD). The two residual heights tested (30 and 60 mm) had minimal impact on NSC reserves during regrowth in either chicory or plantain, likely because the majority of NSC reserves are stored in the roots rather than the stubble. In other plant species, a failure to replenish NSC reserves before the next defoliation is one factor associated with reduced DM production. This also appears to be the case with chicory and plantain, with reductions in DM production occurring if swards are defoliated during NSC mobilisation or the early stages of replenishment (i.e. before 21 days of regrowth or 310 GDD in chicory and 35 days of regrowth or 532 GDD in plantain).

Impact of warming and drought on carbon balance related to wood formation in black spruce.

Wood formation in trees represents a carbon sink that can be modified in the case of stress. The way carbon metabolism constrains growth during stress periods (high temperature and water deficit) is now under debate. In this study, the amounts of non-structural carbohydrates (NSCs) for xylogenesis in black spruce, Picea mariana, saplings were assessed under high temperature and drought in order to determine the role of sugar mobilization for osmotic purposes and its consequences for secondary growth. Four-year-old saplings of black spruce in a greenhouse were subjected to different thermal conditions with respect to the outside air temperature (T0) in 2010 (2 and 5 °C higher than T0) and 2011 (6 °C warmer than T0 during the day or night) with a dry period of about 1 month in June of each year. Wood formation together with starch, NSCs and leaf parameters (water potential and photosynthesis) were monitored from May to September. With the exception of raffinose, the amounts of soluble sugars were not modified in the cambium even if gas exchange and photosynthesis were greatly reduced during drought. Raffinose increased more than pinitol under a pre-dawn water potential of less than -1 Mpa, presumably because this compound is better suited than polyol for replacing water and capturing free radicals, and its degradation into simple sugar is easier. Warming decreased the starch storage in the xylem as well the available hexose pool in the cambium and the xylem, probably because of an increase in respiration. Radial stem growth was reduced during drought due to the mobilization of NSCs for osmotic purposes and due to the lack of cell turgor. Thus plant water status during wood formation can influence the NSCs available for growth in the cambium and xylem.

Grain Yield Response to Planting Density in Forage Rice with a Large Number of Spikelets

ABSTRACTBecause forage rice (Oryza sativa L.) must be cost‐competitive with other forage crops, high grain yield is essential. The objective of the present study was to determine the effects of planting density (11, 25, or 100 hills m−2) and N application method (the 79‐21N method, with 79% of the N applied before the panicle initiation stage and 21% after, or the 36‐64N method, 36% before and 64% after) on grain yield and its components in the cultivar Mizuhochikara, which produces an unusually large number of spikelets per square meter. Grain yield was not different between N application methods but increased from 799 g m−2 to 870 g m−2 with increasing planting density. The number of spikelets per square meter was not strongly influenced by the planting densities. The percentage of filled spikelets and the 1000‐grain weight was higher at 100 and 25 hills m−2 than at 11 hills m−2. The amount of nonstructural carbohydrate (NSC) in the leaf sheaths plus stems per square meter at the full heading stage was larger at 100 and 25 hills m−2 than at 11 hills m−2. The percentages of both primary and secondary spikelets increased with increasing planting density, whereas that of tertiary spikelets decreased. Grain weight per spikelet was generally higher at primary and secondary spikelets than at tertiary spikelets. At each position in the panicle, grain weight per spikelet was heavier at 100 and 25 hills m−2 than at 11 hills m−2. Thus, dense planting may increase the grain yield, the percentage of filled spikelets, and the 1000‐grain weight by increasing NSC at full heading stage and decreasing the number of tertiary spikelets even at a large number of spikelets per square meter in Mizuhochikara.

Remobilization of dry matter in wheat: effects of nitrogen application and post-anthesis water deficit during grain filling

Pre-anthesis stored dry matter in wheat (Triticum aestivum L.) is important in a Mediterranean climate because grain filling greatly depends on the remobilization of pre-anthesis assimilates. A water deficit at the post-anthesis stage may increase the dry matter stored before anthesis. This field study assessed the effects of post-anthesis water deficit and the application of nitrogen (N) fertilizer on three wheat cultivars. Data collected over 2 years showed that, in wheat with a post-anthesis water deficit (WD), dry matter remobilization efficiency reached its maximum (29%) at 80 kg N ha−1, but further additions of N decreased it. The contribution of remobilized dry matter to a grain ranged from 7% to 23% of the grain's dry weight and, in WD grain, was 78% more than that of well-watered (WW) grain. Grain from plots on which fertilizer had been applied had a lower proportion of remobilized dry matter than did grain from unfertilized plots. For grain from adequately fertilized treatments, limited irrigation was associated with reduced dry matter remobilization. The amount of non-structural carbohydrates (NSC) remaining in parts of the plant was much greater in the WW than in the WD treatments. The 160 kg N ha−1 treatment also left more NSC unused than did the no N treatment. The active grain-filling period was shortened substantially by a water deficit, but this was countered by the application of 160 kg N ha−1. Grain-filling rates for all cultivars or all N treatments were increased by inducing a water deficit. For WD grains, kernel weight was reduced when fertilizer application rates were 0–80 kg N ha−1, but increased when rates were 160 kg N ha−1, unlike WW grain exposed to similar fertilizer regimes. The grain yield of WD wheat was reduced by 25%, and that of grain receiving no fertilizer was 15% lower than that receiving 80 kg N ha−1. Among three wheat cultivars, cv. Chamran produced the highest grain yield (19% higher than that of either cv. Shiraz or cv. Marvdasht). It was concluded that the stored carbohydrate had provided an important buffer against water stress during grain filling, in terms of yield.

Changes in chemical composition of hydrophyte leaves during adaptation to aquatic environment

Leaf chemical composition of 19 hydrophytes was studied. The content of carbon, nitrogen, nonstructural carbohydrates, organic acids, minerals, and water was determined. Hydrophytes were shown to contain less carbon (below 410 mg/g dry wt in 60% species) than terrestrial plants. Hydrophytes and terrestrial plants did not differ in the nitrogen concentration in the leaves (33 and 29 mg/g dry wt, respectively). Hydrophytes were characterized by a low content of organic acids (40–90 mg/g dry wt in 60% species) and high content of mineral compounds (90–170 mg/g dry wt in 50% species). Total amount of nonstructural carbohydrates was similar in the leaves of hydrophytes and terrestrial plants (from 120 to 190 mg/g dry wt), but the proportions of various carbohydrate fractions differed substantially. In the hydrophyte leaves, the content of soluble carbohydrates was 2.4-fold lower, whereas the content of nonstructural polysaccharides 1.2-fold higher than in terrestrial plant leaves. Two groups of correlations between parameters of leaf chemical composition were distinguished: the contents of carbon, nitrogen, and soluble sugars were positively correlated, and the negative correlation was observed between these parameters and the amounts of mineral compounds, organic acids, water, and nonstructural polysaccharides. We concluded that hydrophyte leaf chemical composition reflects a specificity of plant adaptation to aquatic environment.

Studies on the digestion in the Giant Panda, Ailuropoda melanoleuca, fed feedstuffs including bamboo

ABSTRACT Two digestion trials by total feces collection method were conducted, using a male adult giant panda in captivity fed feedstuffs including bamboo. Collected pieces of feces were assorted according to undigested feedstuff mainly forming each piece of feces, and analyzed separately. The data were converted into undigested nutrients of each feedstuff with a calculating procedure devised to assess respective digestibility. Cell wall constituents of bamboo were apparently digested to a certain extent, although the digestibility was low (24.1% and 15.0% in Experiment 1 and 2, respectively, in the case of NDF (neutral detergent fiber)). Cellular contents of the bamboo were also less digestible compared with those of the other feedstuffs, while nutrients in less fibrous feedstuffs (concentrates) were digested fairly well (more than 90%). The amount of non structural carbohydrate of bamboo excreted in the feces, exceeded the amount ingested. This fact was considered to be due to imperfect digestion of cel...

High fat intake by ponies reduces both apparent digestibility of dietary cellulose and cellulose fermentation by faeces and isolated caecal and colonic contents

Inclusion of extra fat in the diet of horses, at the expense of an iso-energetic amount of non-structural carbohydrates, has been shown to decrease the apparent digestibility of the various dietary fiber fractions, but the mechanism was unknown. It was hypothesized that inclusion of extra fat in the diet depresses the caecal and/or colon microbial degradation of fiber, leading to a decrease in fiber digestion. The hypothesis was tested using six ponies fed either low fat or a high fat ration. In the ponies, the high fat ration lowered apparent NDFom digestibility by 0.089. The 12 ponies were killed and intestinal contents isolated to be used as inoculum with in vitro gas production technique. In general, groups mean maximum gas production from either cellulose or xylan by caecal, colon and faecal bacteria was lower when the ponies had been fed the high fat diet. Cumulative gas production by caecal fluid with xylan as substrate after 20 h of incubation was depressed when the donor animals had been fed the high fat diet. With cellulose as substrate, gas production by caecal contents was lowered by on average 20% after fat feeding of the ponies. There was a diet effect of cell-free caecal fluid on gas production from cellulose by a standard inoculum: fat feeding had an inhibitory impact. It is concluded that fat feeding in ponies inhibits microbial activity in the caecum, which in turn leads to a decrease in fiber digestibility.

Dry matter intake precalving in cows offered fresh and conserved pasture

Maintaining dry matter intake (DMI) during the last 2 weeks of gestation is difficult, and a failure to do so is reported to have negative implications on postcalving DMI (Grummer, 1995) and subsequent milk production (Bertics et al. 1992). DMI at the end of gestation, but excluding the last 1–2 d before parturition, can decrease by up to 30% (Lodge et al. 1975; Bertics et al. 1992; Dewhurst et al. 2000). The extent of the decline varies and may be influenced by a number of factors, such as level of feeding precalving (Lodge et al. 1975; Murphy, 1999; Dewhurst et al. 2000) or amount of non-structural carbohydrates in the precalving diet (Coppock et al. 1972; Forbes, 1995). Most studies were undertaken with cows receiving total mixed ration (TMR) or conserved forage and concentrates. However, this may have been one of the reasons for the witnessed depression. Increasing the proportion of rapidly fermentable carbohydrates or alternatively decreasing the fibre concentration in the precalving diet appears to exacerbate this decline (Coppock et al. 1972; Minor et al. 1998). Research suggests that ruminants may actively select against concentrates as plasma oestrogen concentrations increase, such as happens in the weeks preceding parturition (Forbes, 1995). When hay was offered ad libitum, increasing concentrations of oestrogen (up to 400 μg infused intravenously) had no effect. However, when a complete pelleted diet was offered, a 90-μg infusion caused a lower feed intake, followed by a significant increase after treatment was stopped. The lack of depression in precalving DMI reported by Coppock et al. (1972) and Vazquez-Anon et al. (1994) when forage was the principal component of the diet, supports this.

Effect of non-structural carbohydrate dietary content on the productive performance of Sarda primiparous ewes

In order to enhance our knowledge of milk sheep rationing, 30 Sarda primiparous ewes, for which single birth was diagnosed by ultrasonography prior to lambing, were divided into two homogeneous groups (L-NSC and H-NSC) and fed isoproteic diets containing different amounts of non-structural carbohydrates (NSC, 36 vs 40 % DM). The lambs were weighed both at birth (between February and March 2002) and at sale (about one month later) in order to estimate milk produced by their mothers during the lactation period, by using a specific equation developed on Sarda ewes. Individual milk yield and quality were then monitored monthly until the ewes dried off (July 2002). Our results showed that group H-NSC (which received the diet with the highest NSC content) was associated to the highest milk yield (P<0.01) during the suckling period. In contrast, in the milking period group L-NSC showed significantly higher (P<0.05) mean milk yield (996.2 vs 899.8 g/d) and fat and protein corrected milk yield (979.6 vs 877.7 g/d). Dietary treatments did not significantly affect milk composition.In conclusion, considering the milk production of each group as a function of the lactation month, group H-NSC had its best performance during the first two months of lactation, while group L-NSC was more productive during the remaining months. Also the percentage of protein, fat and casein of the milk during milking showed a similar trend. While the latter parameters were higher in the H-NSC group during the first two months of milking, from the 4th control onward higher levels were observed in the L-NSC group. These results suggest, at least for Sarda primiparous ewes, the adoption of diets with different contents of non-structural carbohydrates according to the productive period (40 %, DM basis, in the first two months of lactation, 36 %, DM basis, in subsequent months).

Lipid Metabolism in Equines Fed a Fat-Rich Diet

The hypothesis tested was that dietary fat, when compared with an isoenergetic amount of non-structural carbohydrates, stimulates lipolysis in adipose tissue and also stimulates the fatty-acid oxidative capacity in skeletal muscle from horses. Six adult horses were fed a high-fat, glucose or starch containing diet according to a 3 x 3 Latin square design with feeding periods of three weeks. The diets were formulated so that the intake of soybean oil versus either glucose or corn starch were the only variables. In accordance with previous work, whole plasma triacylglycerol (TAG) concentration decreased significantly by 58% following fat supplementation. This fat effect was accompanied by a 247% increase in lipoprotein lipase (LPL) activity in post-heparin plasma. The dietary variables did neither significantly affect the basal in vitro lipolytic rate nor the lipolytic rate after adding noradrenaline. There was no significant diet effect on the activities of hexokinase and phosphofructokinase as indicators of glycolytic flux and citrate synthase and 3-hydroxy-acyl-CoA dehydrogenase as indicators of fatty-acid oxidative capacity. The concentrations of muscle glycogen and TAG were not affected by fat supplementation. It is concluded that our hypothesis is not supported by the present results.

Relationships between the Contents of Carbohydrates and Cell Wall Materials in the Stems of Rice during Grain Filling.

Hitomebore, a popular rice variety in Tohoku, was cultured in 1997 by using standard practice (CON), the practice of nitrogen-free basal dressing with sparse planting (BNo), and BNo with the application of 200 gm-12 of raw rice bran (RB). The contents of nonstructural carbohydrates (NSC), cell wall materials (ADF) and ash in stems (culms and leaf sheaths) were analyzed during the grain filling. The percentage of NSC based on dry weight was higher in BNo and RB than in CON, and also higher in the lower internodes than in upper ones. In contrast, the percentage of ADF was smaller in BNo and RB and in the lower internodes. The contents of ash whose main component is silica, showed that it was quite similar to that of ADF. The correlation coefficient between the percentages of ADF and NSC was negative, but between the percentages of ADF and ash it was positive and highly significant. The correlations for the amount of ADF per unit area with the amounts of NSC and ash were positive and highly significant. The dry weight of stems was closely correlated to the amounts of ADF, NSC, and ash. No correlation was noted with respect to their percentage.

Sulfur Availability, Rubisco Content, and Photosynthetic Rate of Soybean

Understanding the role of S in soybean [Glycine max (L.) Merr.] growth is important because a deficiency of the S‐containing amino acids methionine and cysteine limits the nutritional value of soybean protein. As part of a broader study of S uptake and use, our objective was to quantify the effect of S availability on photosynthetic characteristics of soybean. Kenwood soybean was grown in a 3:1 mixture of Ida silt loam [fine‐silty, mixed (calcareous), mesic Typic Udorthent] and acid washed sand with varying amounts of S added as gypsum (CaSO4) in two greenhouse trials. Single‐leaf CO2‐exchange rate (CER), quantum efficiency, dark respiration, leaf S, leaf N, and Rubisco content were determined. There appeared to be a critical level of 35 mg S per kg mixture (about 85 mg S per plant) below which specific leaf S (mg m−2 leaf area) declined linearly with decreases in soil S availability. On average, the most S deficient plants had 70% lower CER, 42% less quantum efficiency, and 50% decline in dark respiration relative to plants receiving adequate S. Total leaf N and Rubisco content were linearly related to leaf S levels, and declined on average 62, and 95%, respectively, as S declined from approximately 120 to 40 mg S m−2 leaf area. There was a linear relation between CER and Rubisco content; however, the amount of nonstructural carbohydrates per unit leaf N increased two‐fold under S deficiency, suggesting that limitations on sink strength were greater than those on source capacity. Carbon dioxide exchange rate was linearly related to leaf S content at all sample dates, with a mean relation of 216 (μmol CO2 g−1 S s−1. The Rubisco fraction declined linearly from nearly 50 to &lt;10% of soluble protein, as leaf soluble protein content declined under S deficiency. We postulate that the decline in the Rubisco fraction may be a function of increased relative importance of housekeeping enzymes for survival as protein levels decline, and/or down‐regulation of Rubisco synthesis in response to a build up of carbohydrates in the source leaves under S deficiency.

Physiological characteristics of high-yielding rice inferred from cross-location experiments

Understanding the processes controlling yield in well-managed, high-input crops may offer ways of increasing currently recognized yield potentials. In this study, 13 crops of Koshihikari rice were managed with different nitrogen strategies to achieve maximum yield in three environments, Kyoto (6 t ha −1) and Ina (10 t ha −1) in Japan, and Yanco (13 t ha −1) in Australia. A common set of data on radiation interception, growth, yield, yield components, N uptake and non-structural carbohydrates was collected for each crop. There was a similar efficiency of dry matter production per unit of incident global radiation at the three sites, 0.78 g MJ −1. At Yanco, incident and intercepted radiation were high but were offset by a low conversion of intercepted radiation to dry matter (radiation-conversion efficiency, RCE) of 1.0 g MJ −1 compared to RCE = 1.4 at Kyoto and Ina. The RCE at Yanco was particularly low during the grain filling stage, apparently due to poor root function associated with low soil aeration and to low tiller survival and low minimum temperatures. If these constraints could be overcome and the RCE increased to the values in Kyoto and Ina, the estimated yield potential at Yanco would be about 18 t ha −1. Given the relatively high values of RCE at Kyoto and Ina, the most promising way to increase yield potential would be to increase the efficiency of converting growth to grain yield. At all three locations the number of grains was less than the number of spikelets. The quantity of assimilate available for grain production was estimated from the amount of non-structural carbohydrate at heading plus the dry matter growth after heading. The potential sink for assimilate was estimated from the number of florets and the weight of a filled kernel. By comparing these amounts it appeared that some of the crops at Ina were source limited and some were sink limited, while at Kyoto crops were neither clearly source limited nor sink limited. This paradoxical result is explained by a lack of assimilates soon after heading, leading to poor grain set, followed by a surplus of assimilates during late grain filling. On the basis of other evidence, there appears to be genetic variability for the ability to set grains in conditions of poor assimilate supply, suggesting that in the low-radiation environments in which much rice is grown, there may be scope for increasing yield by increasing the number of fertile florets.

Chemical changes associated with the field drying of oat forage

Two trials measured changes in the crude protein, degradable protein, non-protein nitrogen, acid detergent insoluble nitrogen, non-structural carbohydrates and cell-wall fractions of oat herbage ( Avena sativa L.) during air drying to make hay. Plant materials were whole aerial parts and separated leaf blade and non-leaf blade components (stems plus leaf sheaths and inflorescences). The non-protein nitrogen content in the standing crop was 4.1 and 3.5 g kg −1 and increased to 6.6 and 8.1 g kg −1 in hay, in 1991 and 1992, respectively. Field drying produced a significant decrease ( P < 0.05) in the amount of non-structural carbohydrates, the values decreasing from 303 to 228 g kg −1 and from 225 to 177 g kg −1, depending on the year. These changes produced higher concentration of cell-wall fractions in hay. In general, the chemical changes followed a similar pattern in both leaf blade and non-leaf blade materials. As a consequence of these changes, oat hay supplies less readily fermentable energy relative to ruminal N degradation than does fresh forage.