Starch Accumulation In Grains Research Articles

As(III)-oxidizing and plant growth-promoting bacteria increase the starch biosynthesis-related enzyme activity, 2-AP levels, and grain quality of arsenic-stressed rice plants

BackgroundGrain quality is an important index of rice production, particularly when plants are grown under stress. Arsenic (As) contamination in paddy fields severely affects rice grain yield and quality. Here, the effects of As and combinations of As(III)-oxidizing bacteria (Pseudomonas stutzeri 4.25, 4.27, and 4.44) and plant growth-promoting bacteria (Delftia acidovorans KKU2500-12 and Cupriavidus taiwanensis KKU2500-3) on enzymes related to starch accumulation in grains and the grain quality of Khao Dawk Mali 105 rice cultivated in As-contaminated soil under greenhouse conditions were investigated.ResultsArsenic affected the activities of starch biosynthesis-related enzymes, and decreases of up to 76.27%, 71.53%, 49.74%, 73.39%, and 47.46% in AGPase, SSS, GBSS, SBE, and SDBE activities, respectively, and 9.42–61.07% in starch accumulation in grains were detected after growth in As-contaminated soil. However, the KKU2500-3/4.25 and KKU2500-3/4.44 combinations yielded the greatest enzyme activities in grains, and compared with the results observed in uninoculated seedlings, increases in starch accumulation of up to 51.16% and 23.81% were found in the inoculated seedlings after growth in medium- and high-As-contaminated soils, at 10–17 and 10–24 days after anthesis, respectively. The bacteria increased the 2-AP content in rice under As stress, possibly via the induction of proline, a 2-AP substrate. Bacterium-inoculated rice had significantly greater 2-AP levels than uninoculated rice, and 2.16–9.93% and 26.57–42.04% increases were detected in rice plants grown in medium- and high-As-contaminated soils, respectively.ConclusionsArsenic toxicity can be mitigated in rice growing under greenhouse conditions by maintaining starch biosynthesis, accumulating amylose, and increasing 2-AP content. The effectiveness of these bacteria should be validated in paddy fields; hence, safe rice grains with a good starch content and aroma could be produced.

Effects of nitrogen fertilizer and chemical regulation on spring maize lodging characteristics, grain filling and yield formation under high planting density in Heilongjiang Province, China

Now, lodging is a major constraint factor contributing to yield loss of maize (Zea mays L.) under high planting density. Chemical regulation and nitrogen fertilizer could effectively coordinate the relationship between stem lodging and maize yield, which significantly reduce lodging and improve the grain yield. The purpose of this study was to explore the effects of chemical regulation and different nitrogen application rates on lodging characteristics, grain filling and yield of maize under high density. For this, we established a field study during 2017 and 2018 growing seasons, with three nitrogen levels of N100 (100 kg ha–1), N200 (200 kg ha–1) and N300 (300 kg ha–1) at high planting density (90 000 plants ha–1), and applied plant growth regulator (Yuhuangjin, the mixture of 3% DTA-6 and 27% ethephon) at the 7th leaf. The results showed that chemical control increased the activities of phenylalanine ammonia-lyase (PAL), tyrosine ammonia-lyase (TAL), 4-coumarate:CoA ligase (4CL), and cinnamyl alcohol dehydrogenase (CAD), and increased the lignin, cellulose and hemicellulose contents at the bottom of the 3rd internode, which significantly reduced the lodging percentage. The lignin-related enzyme activities, lignin, cellulose and hemicellulose contents decreased with the increase of nitrogen fertilizer, which significantly increased the lodging percentage. The 200 kg ha–1 nitrogen application and chemical control increased the number, diameter, angle, volume, and dry weight of brace roots. The 200 kg ha–1 nitrogen application and chemical control significantly increased the activities of ADP-glucose pyrophosphorylase (AGPase), soluble starch synthase (SSS) and starch branching enzyme (SBE), which promoted the starch accumulation in grains. Additional, improved the maximum grain filling rate (Vmax) and mean grain filling rate (Vm), which promoted the grain filling process, significantly increased grain weight and grain number per ear, thus increased the final yield.

High night temperature induced changes in grain starch metabolism alters starch, protein, and lipid accumulation in winter wheat.

Unlike sporadic daytime heat spikes, a consistent increase in night-time temperatures can potentially derail the genetic gains being achieved. Ten winter wheat genotypes were exposed to six different night-time temperatures (15-27°C) during flowering and grain-filling stages in controlled environment chambers. We identified the night-time temperature of 23o C as the critical threshold beyond which a consistent decline in yields and quality was observed. Confocal laser scanning micrographs of central endosperm, bran, and germ tissue displayed differential accumulation of protein, lipid, and starch with increasing night-time temperatures. KS07077M-1 recorded a decrease in starch and an increase in protein and lipid in central endosperm with increasing night-time temperatures, whereas the same was significantly lower in the tolerant SY Monument. Expression analysis of genes encoding 21 enzymes (including isoforms) involved in grain-starch metabolism in developing grains revealed a high night-time temperature (HNT)-induced reduction in transcript levels of adenosine diphosphate glucose pyrophosphorylase small subunit involved in starch synthesis and a ≥2-fold increase in starch degrading enzymes isoamylase III, alpha-, and beta-amylase. The identified critical threshold, grain compositional changes, and the key enzymes in grain starch metabolism that lead to poor starch accumulation in grains establish the foundational knowledge for enhancing HNT tolerance in wheat.

Comparison of Structural and Functional Properties of Wheat Starch Under Different Soil Drought Conditions

Drought influences cereal crop yield and quality. However, little is known about changes in the structural and functional properties of wheat starch under soil drought conditions. In this study, two wheat cultivars were subjected to well-watered (WW), moderate soil-drought (MD), and severe soil-drought (SD) from 7 tillers in the main stem to maturity. The structural and functional properties of the resultant endosperm starch were investigated. In comparison with WW soil, the MD increased starch accumulation in grains, the proportion of large starch granules, amylose and amylopectin long branch chain contents, and average amylopectin branch chain length, which were accompanied by the increase in activities of granule bound starch synthase and soluble starch synthase. MD treated-starch had a lower gelatinization enthalpy, and swelling power, but a higher gelatinization temperature, retrogradation enthalpy, and retrogradation percentage when compared to WW conditions. The MD also increased starch resistance to acid hydrolysis, amylase hydrolysis, and in vitro digestion. The SD had the opposite effects to the MD in all cases. The results suggest that soil drought more severely affects amylose synthesis than amylopectin synthesis in wheat grains, and moderate soil-drought improves molecular structure and functional properties of the starch.

Effect of Drought Stress During Flowering Stage on Starch Accumulation and Starch Synthesis Enzymes in Sorghum Grains

Starch content is a key factor affecting sorghum grain quality. The research of sorghum grain starch accumulation and the related synthesis enzyme activities has great significance for understanding the mechanisms of starch metabolisms. The differences between a high and a low starch content sorghum hybrids (Tieza 17 and Liaoza 11, respectively) in grain starch accumulation and the related synthesis enzyme activities were assessed following imposition of water stress during flowering stage. The total starch, amylase and amylopectin accumulation all decreased at the mid-late stage of grain filling under drought stress during flowering stage. The maximum and mean accumulation rates also decreased. During grain filling, soluble starch synthase (SSS), granule-bound starch synthase (GBSS), starch branching enzyme (SBE), and starch debranching enzymes (DBE) activities were all affected, though differently. Drought stress reduced starch accumulation in a larger extent for Tieza 17 than Liaoza 11. Drought stress during flowing stage reduced starch synthesis enzyme activities, thus reducing starch accumulation in grains, and the differences between starch components were also demonstrated under drought stress.

Relationship of Endogenous ABA and IAA to Accumulation of Grain Protein and Starch in Two Winter Wheat Cultivars under Post-anthesis Water Deficit

Accumulation of protein and starch in grain is a key process determining grain yield and quality in wheat. Under drought endogenous plant hormone levels will change and may have an impact on the yield and quality of wheat. In a greenhouse experiment, two winter wheat (Triticum aestivum L.) varieties differing in post anthesis drought resistance, tolerant (cv. Zagros) and sensitive (cv. Marvdasht), were subjected to either well-watered (WW) or water-stressed (WS) from anthesis to maturity. On the 7, 15 (grain enlargement stage) and 31 (grain filling stage) days after anthesis (DAA), endogenous abscisic acid (ABA) and indole-3-acetic acid (IAA) were determined in grain of wheat plants by enzyme linked immunosorbent assay (ELISA). The patterns of hormonal changes were similar in two varieties. The ABA levels were much higher under water deficit than well water treatment. In comparison grain ABA levels in all sampling stages was more in Marvdasht than Zagros. The endogenous grains IAA content display a marked reduction by the time and the water stress aggravated this reduction in both cultivars, however, the depresstion was more in drought-sensitive than drought-tolerant. The relationship between yields and contents of starch and protein in grains and levels of two hormones in sink organ indicated that the changes in yield and content of grain starch and protein under water withholding were associated with the reduced IAA and elevated ABA level in grains. It was proposed that the changed levels of endogenous hormones under drought post-anthesis might indirectly affect protein and starch accumulation in grains by influencing the regulatory enzymes and processes.

Identification and expression pattern of ribosomal L5 gene in common wheat ( Triticum aestivum L.)

The full-length cDNA sequence (1158 bp) encoding a ribosomal L5 protein, designated as TaL5, was firstly isolated from common wheat ( Triticum aestivum L.) using the rapid amplification of cDNA ends method (RACE). The open reading frame (ORF) of TaL5 gene was 906 bp, and its deduced amino acid sequence (301 residues) shared high similarity to those of other higher plant L5 proteins. TaL5 protein contained a putative 5S binding region (74 amino acids). TaL5 DNA sequence was further cloned, and sequence analysis showed that it contained 7 introns and 8 exons. Predicated using TargetP software, TaL5 protein was putatively located in mitochondria and contains a transit peptide of 12 amino acids. During grain filling period, temporal expression pattern of TaL5 gene was approximately consistent with the rates of starch accumulation in grains. Additionally, TaL5 gene was dramatically induced by salt, drought and freezing stresses, exogenous abscisic acid (ABA) and salicylic acid (SA) in wheat seedlings. These implied that TaL5 gene could function in growth, development and abiotic stresses in wheat plants.

Effects of ADP-Glucose Pyrophosphorylase Activity on Sterility and Develop-ment of Grain in K, V, and T-Cytoplasmic Male

Cytoplasmic male-sterile (CMS) lines, especially K (Aegilops kotchyi), V (Aegilops ventricosa), and T (Triticum timopheevi) types of cytoplasms, are of high value in heterosis utilization in wheat (Triticum aestivum L.). The sterile mechanisms of these CMS types have been focused in hybrid wheat research. As a key and rate-limiting starch biosynthetic enzyme, ADP-glucose pyrophosphorylase (AGPase) is considered to play an important role in the sterility of CMS lines. For gaining an insight into the physiological basis of the sterility in CMS lines of wheat, the activities of AGPase in leaves, young spikes, and grains were measured in K, V, and T types of isogenic CMS lines (Ji 5418 background) at different growth stages, and compared with those of their maintainer line. The dynamic accumulations of starch, amylose, and amylopectin were also investigated in both superior (the first and the second grains in a spikelet) and inferior (grains except for the first and the second grains in a spikelet) grains. In young spikes, the AGPase activities of the three CMS lines were significantly higher (F=133.81, P＜0.0001) with the differences of 9.33-27.94 μmol g^(-1) FW h^(-1) at floret primordium stage, and significantly lower (F=13.97-75.20, P＜0.0001) by 4.27-7.44 μmol g^(-1) FW h^(-1) at tetrad stage as compared with the maintainer line. From floret primordium to tetrad stage, the CMS lines had continuously higher level of AGPase activities in leaves than the maintainer line, with the differences ranged from 7.39 to 80.77 μmol g^(-1) FW h^(-1) (F=135.76-5454.28, P＜0.0001). Compared with the maintainer line, the three CMS lines all presented lower accumulations (P＜0.05) of starch, amylose and amylopectin in grain. The starch content and AGPase activity in superior grains were significantly higher than those in inferior grains for CMS lines. The dynamic accumulations of starch in superior and inferior grains fitted Logistic equations, and positively correlated with the starch accumulation rate (r=0.4460-0.7150, P=0.0004-0.0487). The AGPase activity in leaves had an insignificantly negative correlation with net photosynthetic rate. In conclusion, the male sterility is probably in relation to the insufficiency of energy in leaves and young pikes at floret primordium stage resulting from the high AGPase activity, and the low accumulation of starch in pollens at tetrad stage caused by low AGPase activity in young spikes. The sterile cytoplasm has a negative effect on AGPase activity, resulting in decreases of ADPG level and starch accumulation in grains. Besides, the negative effect of AGPase activity on net photosynthetic rate in flag leaves may result in unfilled grains in CMS lines.

Difference in AGPase subunits could be associated with starch accumulation in grains between two wheat cultivars

The rates of starch accumulation, the activities of ADP-glucose pyrophosphorylase (AGPase, the key enzyme of starch synthesis), and the transcript levels of its four subunits were measured and compared between two large-spike winter wheat cultivars (Yujiao 2 and Lankao Aizao 8) during the periods of grain filling. During the first 10 days of grain filling periods, there were no differences in the rates of starch accumulation and activities of AGPase between the two wheat cultivars. In subsequent filling periods, however, the rates of starch accumulation and activities of AGPase in grains of cv. Yujiao 2 were significantly higher than those in cv. Lankao Aizao 8. cDNA sequences for four subunits of AGPase (cytosolic small subunit, SSU I; plastidial small subunit, SSU II; cytosolic large subunit, LSU I and plastidial large subunit, LSU II) were amplified, and their transcript levels during the whole grain filling were measured using semi-quantitative RT–PCR. No difference in transcript levels of SSU I, SSU II and LSU II was found between the two wheat cultivars during the whole grain filling period. However, the transcript levels of LSU I showed an obvious difference since 15 days of anthesis between two wheat cultivars, and LSU I transcripts were higher in cv. Yujiao 2 than those in cv. Lankao Aizao 8. This was clearly consistent with those in the starch accumulation rates and AGPase activities, implying that LSU I transcript levels could be related to the differences in the activities of AGPase and rates of starch accumulation.

Effects of High Temperature on Key Enzymes Involved in Starch and Protein Formation in Grains of Two Wheat Cultivars

AbstractHigh temperature is a major determinant of grain growth and yield formation in wheat. The present study was undertaken to investigate the effects of high temperature regimes on the activities of key regulatory enzymes involved in starch and protein accumulation in grains of two winter wheat (Triticum aestivum L.) cultivars Yangmai 9 and Xuzhou 26 with different protein contents. Four day/night temperature regimes of 34 °C/22 °C, 32 °C/24 °C, 26 °C/14 °C and 24 °C/16 °C were established after anthesis, resulting in two daily temperature levels of 28 °C and 20 °C and two diurnal temperature differences of 12 °C and 8 °C. The activities of glutamine synthase (GS) in flag leaves and glutamate pyruvic aminotransferase (GPT), sucrose synthase (SS), soluble starch synthase (SSS) and granule‐bound starch synthase (GBSS) in grains were measured during the periods of grain filling. High temperature reduced both content and yield of starch in grains, while enhanced protein content and reduced protein yield in grains. High temperature significantly enhanced the activities of SS and GBSS on 14 days after anthesis (DAA). High temperature affected SSS slightly in Yangmai 9, but reduced SSS activity markedly in Xuzhou 26 on 14 DAA. However, at the middle and late stages of grain filling, high temperature reduced the activities of SS, GBSS and SSS significantly in the two wheat cultivars. High temperature reduced GPT activity in grains in the two wheat cultivars, but reduced GS activity in flag leaves of Yangmai 9 and enhanced GS activity of Xuzhou 26 on 14 DAA. In addition, under the same high temperature level, SS activity was higher at 34 °C/22 °C, whereas the activities of SSS and GBSS were higher at 32 °C/24 °C. Also, diurnal temperature differences affected GPT and GS activities differently between the two cultivars. Under optimum temperature level, the activities of key enzymes for starch and protein synthesis were higher at 26 °C/14 °C. The activities of SS, SSS and GBSS significantly correlated with starch accumulation in grains, except for GBSS activity to starch content on 14 DAA. GPT activity was positively correlated with protein yield, and GS activity was negatively correlated with protein yield on 14 DAA, while the activities of both GPT and GS were negatively related to protein content in grains.

Modeling plant carbon flow and grain starch accumulation in wheat

The process of starch accumulation in grain directly influences the yield and quality formation in wheat. Since few studies have been aimed at modeling the grain starch accumulation, this study was undertaken to develop a simplified process model for predicting the rate of starch accumulation in wheat grain by focusing on the variation of plant carbon dynamics post-anthesis. Five different experiments involving genotypes, nitrogen rates and water regimes were conducted to support model development and model evaluation. The model proposed that the starch accumulation rate (STR) in individual grain was determined by the availability of carbon source in plant (GCA i ) and the ability of starch synthesis in grain ( f( A i )), as influenced by the factors of temperature, water and nitrogen conditions within plants. The f( A i ) could be described in a two-section curve with post-anthesis growing degree days (GDD), first exponential increase and then linear decrease. The GCA i was determined by post-anthesis carbon assimilation and carbon remobilization from vegetative organs to grains. A genotypic parameter was incorporated into the model algorithm, i.e. the maximum rate of individual grain starch accumulation, to differentiate the ability of starch accumulation among cultivars. The overall performance of the model was validated with different data sets from three field experiments spanning 3 years and comprising various genotypes, nitrogen and water levels. The RMSE values for all treatments were averaged as 12.51%, indicating a good fit between the simulated and observed data. It appears that the model can give a reliable prediction for grain starch accumulation of different wheat cultivars under various growing conditions.

Relationships of endogenous plant hormones to accumulation of grain protein and starch in winter wheat under different post-anthesis soil water statusses

Accumulation of protein and starch in grain is a key process determining grain yield and quality in wheat. Under drought or waterlogging, endogenous plant hormone levels will change and may have an impact on the yield and quality of wheat. In a greenhouse experiment, four winter wheat (Triticum aestivum L.) varieties differing in grain protein content, Heimai 76, Wanmai 38, Yangmai 10 and Yangmai 9, were subjected to drought (SRWC = 45∼50%, DR), waterlogging (WL) and moderate water supply (SRWC = 75∼80%, CK), beginning from 4 days post-anthesis (DPA) to maturity. On the 10 (grain enlargement stage) and 20 (grain filling stage) DPA, endogenous abscisic acid (ABA), gibberellins (GA1+3), indole-3-acetic acid (IAA) and zeatin riboside (ZR) were determined in sink and source organs of wheat plants by enzyme linked immunosorbent assay (ELISA). The patterns of hormonal changes were similar in four varieties. The ABA levels were much higher under DR and WL than under CK. Compared with CK, GA1+3 levels in whole-plant under DR and WL changed a little at 10 DPA, but markedly decreased under DR and WL at 20 DPA. Changes of endogenous IAA level under DR and WL exhibited a complicated pattern, depending on organs and growth stages. Particularly at the 20 DPA, the mean levels of IAA in roots, leaves and grains decreased significantly under DR and WL. In comparison with CK, ZR levels in all organs significantly decreased under DR and WL at both stages. The correlation analyses between yields and contents of starch and protein in grains and levels and ratios of four hormones in source and sink organs indicated that the changes in yield and content of grain starch and protein under DR and WL were associated with the reduced IAA, ZR and GA1+3 levels and elevated ABA level in plants, especially in grains. It was proposed that the changed levels of endogenous hormones under post-anthesis DR and WL might indirectly affect protein and starch accumulation in grains by influencing the regulatory enzymes and processes.

Activities of enzymes involved in sucrose-to-starch metabolism in rice grains subjected to water stress during filling

Slow grain filling of rice ( Oryza sativa L.) is a problem due to the heavy use of nitrogen fertilizer or the high lodging resistance of some cultivars. This study investigated if controlled water deficit during grain filling could enhance sink strength by regulating key enzymes involved and lead to faster grain filling. Two rice cultivars with high lodging resistance and slow grain filling were grown in the field and treated with either normal nitrogen (NN) or high nitrogen (HN) at heading. Well-watered (WW) and water-deficit stressed (WS) treatments were imposed from 9 days after anthesis (DAA) until maturity. Leaf water potentials of both cultivars markedly decreased during the day as a result of WS treatments, but completely recovered by early morning. WS promoted the reallocation of prefixed 14 C from stems to grains, facilitated starch accumulation in grains and increased grain-filling rate although it shortened grain-filling period. In contrast, HN behaved in the opposite way. Sucrose synthase (EC 2.4.1.13) activity was substantially enhanced by water stress, and was positively correlated with starch accumulation rate (SAR) in the grains. Both soluble and insoluble invertase (EC 3.2.1.26) activities were less enhanced by WS and showed no significant correlation with SAR. Starch branching enzyme (BE) (EC 2.4.1.18) and soluble starch synthase (EC 2.4.1.18) activities were also enhanced by the WS, with the former enhanced more than the latter, and were significantly correlated with SAR. Adenine diphosphoglucose pyrophosphorylase (EC 2.7.7.27) activity was little affected by WS. The results suggest that WS-increased remobilization and grain-filling rate were attributed to enhanced sink strength by regulating sucrose synthase and starch BE activities in rice grains when subjected to water stress during the grain-filling period.

Accumulation of starch in wheat grain under different shoot/root temperatures during maturation.

The impact of high temperatures on accumulation of starch in the grain of wheat (Triticum aestivum L.) is usually attributed to direct effects of the stress on the enzymes involved. However, roots are extremely sensitive to temperatures that can be as high as those experienced by the shoots, and their role in whole-plant responses should be considered. Wheat (cv. Len) was grown at 15/15, 30/15, 15/30, and 30/30˚C shoot/root temperatures during maturation, and accumulation of dry matter and N, contents of sucrose and starch, and activities of enzymes in the pathway of starch assimilation in the endosperm, were measured weekly. Dry matter and N accumulation were affected more by root than by shoot temperatures. High whole-plant temperatures (30/30˚C) accelerated linear grain growth but diminished the duration of assimilation, the contents of sucrose and starch, and the activities of the enzymes involved. The effects of high root temperature (15/30˚C) resembled those of high whole-plant temperature, whereas low root temperature (30/15˚C) tended to ameliorate them. Sucrose synthase and soluble starch synthase were affected more than the other enzymes by high shoot and/or root temperature. However, treatments that caused the lowest activities resulted in the fastest, but briefest, linear rates of grain growth. We concluded that shoots and roots interact in the response of wheat to high temperature, and that stress on both organs affects accumulation of starch in grain.

Source‐Sink Manipulations and Carbohydrate Metabolism in Maize

Grain filling is largely dependent on C export from source leaves, but little attention has been given to the use of leaf carbohydrate metabolism criteria for evaluating grain‐filling capacities. This study was conducted to test the effect of source‐sink manipulations on the relationship between starch accumulation in grain and leaf sucrose‐phosphate synthase activity for different maize genotypes. Field‐grown maize (Zea mays L.) plants were subjected to ear removal or to leaf excision at pollination, to examine the effect on regulation of C fixation and partitioning in source leaves during grain filling. At the plant level, the two treatments produced unbalanced effects: ear removal led to accumulation of dry matter in stalks, leaf sheaths, and blades and accelerated senescence of vegetative parts, whereas excision of most leaves hardly affected the remaining leaf and stalk, but drastically reduced the number of developing grains. Modifications in source leaves were estimated from leaf disks punched out in the first leaf above the ear. In this leaf, ear removal caused an increase in soluble sugars 10 days after pollination (DAP), a decrease in sucrose‐P synthase activity (20 DAP), an increase in adenosine dipbosphate glucose pyrophosphorylase activity (30 DAP), a decline of phosphoenolpyruvate (PEP) carboxylase (30 DAP) and of ribulose‐bisphosphate carboxylase (40 DAP). The onset of senescence was marked by an earlier increase in glucose and fructose, and in nonspecific phosphatases. In contrast, leaf excision did not affect senescence compared with control plants and the feedforward effect on source leaves was limited to a transient stimulation of PEP carboxylase (I0 DAP) and a doubling sucrose‐P synthase activity for 40 DAP. Leaf soluble sugars were only slightly depressed, but massive kernel abortion occurred and few grains filled normally. Aborting grains were shown to lack the usual maximum in soluble sugar at 30 DAP. Collectively, the results show that at the grain‐filling stage, sucrose‐P synthase activity more accurately reflected assimilate demand than did metabolite level or enzyme activity for C fixation.

Effect of dihydrostreptomycin spray upon the grain development and carbohydrate content of rice

Spraying with dihydrostreptomycin (Dsm) has been reported to be effective for control of bacterial leaf blight of rice, incited by Xanthomonas oryzae, but occasionally causes reduction of the grain yield. The present experiment showed that, two or three times applications of Dsm to rice plant, including spray at the stage of flowering, caused reduction in the percentage of grains of standard weight, but not in the number of panicles per plant nor number of spikelets per panicle. It was also indicated that Dsmspray at the flowering stage did not effect fertilization, but caused reduction in average grain weight, suggesting a retarding effect on the ripening process of rice grains. Quantitative analysis was made for sugar and starch in the selected organs of rice plant, sprayed with Dsm (1000ppm) at the flowering stage. It was revealed that contents of total sugar, reducing sugar, and starch in the flag leaf of rice plant sprayed, were equal to those of check. Sugar and starch contents in the sheath and culm of plant subjected to spray with Dsm were greater than those of check. In the grains, however, sugar content of the sprayed plant was much greater, and starch was considerably less, than that of check. Accordingly, the difference in sugar content between flag leaf and grain of Dsm-sprayed plant was considerably small as compared with that of checkplant. It is suggested that Dsm-spray may give an inhibitory effect to translocation of sugar from flag leaf to grain and starch accumulation in grain of rice plant.