Shao-Hui Zheng

Effects of carbon dioxide enrichment during different growth periods on flowering, pod set and seed yield in soybean

Abstract The objective of this study is to elucidate the effects of CO2 enrichment during different growth periods on flowering, pod set and seed yield in soybean (Glycine max (L.) Merr.). Soybean cultivar‘Fukuyutaka’was grown in a growth chamber of the Institute of Bioresources Research Center of Kyushu Electric Power Co., Inc. at Saga, Japan (33°17’-N, 130°18’-E) under natural light. The CO2 concentrations were maintained at 350 µmol mol−1 for ambient CO2 and at 700 µmol mol−1 for CO2 enrichment. CO2 concentration was elevated during the whole growth period (WP), vegetative growth period (VP) or reproductive period (RP). Seed yield was increased by CO2 enrichment during RP or WP due to the increase of pod number, but not by CO2 enrichment during VP.Although CO2 enrichment had no effect on the number of flowers, CO2 enrichment during RP increased the pod number on all raceme orders and that during WP increased the pod number in the secondary and tertiary racemes. It is suggested that an increase of seed yield by CO2 enrichment is mostly brought by the improvement of pod set, mainly on the high-order racemes that opened later during flowering period, and that the response of seed yield to CO2 enrichment is mainly attributed to the response during RP.

Genotypic adaptation of soybean to late sowing in southwestern Japan.

Abstract In southwestern Japan, late sowing of soybean is an option that may avoid the damage caused by excessive soil moisture during the rainy season. We investigated the adaptability to late sowing using 17 genotypes from 5 countries. The seeds were sown on 15 – 20 July, and 2 – 5 August in the normal and late sowing seasons, respectively, in an upland field in Karatsu, southwestern Japan in 2009, 2010 and 2011. Late sowing reduced the seed yield by 28.1% and 21.8% on average in the 2009 and 2011 experiments, respectively, whereas it had almost no effect in 2010, in which the temperature was high from sowing to flowering. Seed yield was not improved by increasing the growth period with a longer juvenile growth stage in the genotypes that originated in tropical areas. In the late sowing, seed yield was significantly correlated with the reproductive period from flowering to maturity and pod number, but not with the vegetative period from sowing to the end of leaf expansion or seed size. Soybean cultivars Caviness (USA), Parana and IAS-5 (Brazil), and Akisengoku and Akiyoshi (Japan) showed higher productivity in both types of sowing season, and their seed yields were less reduced by late sowing. These genotypes generally have larger pod number and seed number or longer seed filling periods, but they have medium-size seeds. Our results indicate that the seed yield in late sowing could be improved by the selection of adaptive genotypes that have larger seed number and/or longer seed filling periods.

Varietal Difference in Nitrogen Redistribution from Leaves and Its Contribution to Seed Yield in Soybean

A large amount of nitrogen is redistributed from vegetative organs to the seeds during seed filling in soybean (Glycine max [L.] Merrill). However, the effect of nitrogen redistributed from leaves on the seed yield production is not clear. We evaluated the varietal difference in nitrogen redistribution and its contribution to the seed yield. Ten soybean cultivars were cultivated under conventional conditions in the field in Saga, Japan. The plant samples were collected at various reproductive stages, and then the nitrogen contents in each part were determined. The redistributed nitrogen was estimated by the difference in the nitrogen contents of leaves between the plants at the R5 and R7 stages. The nitrogen content of leaves began decreasing after R5 stage in all cultivars, indicating the start of nitrogen redistribution. About 13.8% to 37.9% of the total nitrogen in the seeds was estimated to have been redistributed from the leaf tissues in the ten cultivars. The seed yield was correlated positively with the amount of redistributed nitrogen from leaves but neither with the nitrogen concentration in the leaves at R5 nor with the proportion of redistributed nitrogen in the seeds. However, in high seed yielding years, 2008 and 2009, the seed yield was not associated with nitrogen redistribution; and the lowest nitrogen redistribution was associated with a relatively high seed yield in Tamahomare. Our results indicated that redistribution of a large amount of nitrogen does not always contribute to high seed yielding, implying the direct nitrogen uptake during seed filling could be more important factor for high seed yielding depending on the cultivars.

Nitrogen redistribution and its relationship with the expression of GmATG8c during seed filling in soybean

It is well known that some nitrogen in the vegetative organs is redistributed to the seeds during seed filling in soybean (Glycine max [L.] Merrill). This redistribution is considered to affect the seed yield of soybean. However, it is still not clear when the nitrogen moves from the vegetative part to the seeds, and the relationship between nitrogen redistribution and leaf senescence has not been clarified. The soybean variety Fukuyutaka was grown in the experimental field of Saga University, Japan from 22 July to 31 October, 2014. After the first flower stage (R1), the plant samples were collected weekly and were separated into leaf, petiole, stem, podshell and seed. The nitrogen concentrations in each plant part were determined. Fresh leaf samples were provided for the determination of soluble protein and autophagy gene GmATG8c expression. The nitrogen that accumulated in the vegetative parts reached its highest level at 60days after sowing (DAS), then began to decrease at 73DAS (R6). This decrease is considered to be the consequence of nitrogen redistribution from the vegetative parts to the seeds. The movement of nitrogen from the vegetative parts to the seeds was estimated to occur at around 73DAS (R6). At this stage, leaf SPAD values, leaf nitrogen, and soluble protein concentrations began to decrease simultaneously, suggesting the onset of leaf senescence. Furthermore, the expression of the autophagy gene GmATG8c in the leaves increased dramatically from 73 to 85DAS, which is the duration of nitrogen redistribution. The results suggest that the nitrogen redistribution from the vegetative parts to the seeds could be one of the initiating factors of leaf senescence, and the autophagy gene GmATG8c was associated with this process.

Metabolite profiling of sheath blight disease resistance in rice: in the case of positive ion mode analysis by CE/TOF-MS

Abstract Rice sheath blight is an important disease caused by Rhizoctonia solani. The resistant and susceptible rice lines (32R and 29S, respectively) showed different responses to R. solani infection in metabolite levels. The aim of this study was to characterize the metabolite levels in rice lines during R. solani infection using capillary electrophoresis equipped with time of flight mass spectrophotometry (CE/TOF-MS) in positive ion mode. Hundred metabolites were identified and classified into six clusters by hierarchical cluster using Mass Profiler Professional software. Changes in metabolite level at inoculated 32R and 29S were mapped on branches of tricarboxylic acid and glycolysis pathway. Volcano plot successfully filtered the metabolites based on fold change and p-value. The volcano plot result showed that 10 metabolites were up and down regulated in inoculated 32R relative to 29S. One metabolite, chlorogenic acid, showed a positive response in 32R. Meanwhile, pipecolic acid showed as the highest magnitude of fold change and p-value significance level in 29S. In addition, eight amino acids; glutamate, γ-aminobutyric acid, glycine, histidine, phenylalanine, serine, tryptophan, and tyrosine showed increase in 29S after R. solani inoculation.

Metabolomic study of two rice lines infected by Rhizoctonia solani in negative ion mode by CE/TOF-MS.

Rhizoctonia solani is a fungal pathogen that causes sheath blight disease in rice plants. In this study, metabolomic analysis using CE/TOF-MS in negative ion mode was used to investigate the resistance response of resistant and susceptible rice lines (32R and 29S, respectively) due to R. solani infection. Two rice lines showed different responses to the infection of R. solani. In 32R, R. solani infection induced significant increases in adenosine diphosphate (ADP), glyceric acid, mucic acid and jasmonic acid. In 29S, inosine monophosphate (IMP) was involved in the plant response to R. solani infection. Phenol compounds showed an increase as a response of the rice lines to R. solani infection. The study suggests that R. solani infection effects in 32R are associated with the induction of plant metabolic processes such as respiration, photorespiration, pectin synthesis, and lignin accumulation. In 29S, the R. solani infection is suggested to correlate with nitrogen metabolism.

An improved method for the simultaneous determination of photosynthetic O2 evolution and CO2 consumption in Rhizophora mucronata leaves

The photosynthetic gas-exchange has been assessed traditionally either as O2 evolution or CO2 consumption. In this study, we used a liquid-phase O2 electrode combined with CO2 optodes to examine simultaneously photosynthesis in intact leaves of mangrove Rhizophora mucronata. We verified suitable conditions for leaf photosynthetic rates by assessing pH levels and NaHCO3 concentrations and compared these to the gas-exchange method at various PAR levels. The photosynthetic rate in response to pH exhibited a similar pattern both for O2 evolution and CO2 consumption, and higher rates were associated with intermediate pH compared with low and high pH values. The net photosynthetic quotient (PQ) of R. mucronata leaves ranged from 1.04–1.28. The PQ values, which were never lesser than 1, suggested that photorespiration did not occur in R. mucronata leaves under aqueous conditions. The similar maximum photosynthetic rates suggested that all measurements had a high capacity to adjust the photosynthetic apparatus under a light saturation condition. The simultaneous measurements of O2 evolution and CO2 consumption using the Clark oxygen electrode polarographic sensor with the CO2 optode sensor provided a simple, stable, and precise measurement of PQ under aqueous and saturated light conditions.

Influence of Nitrogen Enrichment during Reproductive Growth Stage on Leaf Nitrogen Accumulation and Seed Yield in Soybean

Abstract Nitrogen assimilation during seed filling limits the seed yield in soybean. Seed nitrogen dependence on either redistributed nitrogen or absorbed nitrogen from soil during seed filling shows varietal differences. The objective of this study was to investigate the timing of nitrogen enrichment for effective nitrogen assimilation. Two soybean cultivars Sachiyutaka and Tamahomare were sown in the pots filled with well-washed fine sand. The plants were well watered with nutrient solution containing 100 ppm nitrogen and other nutrient elements before and after the treatment. The treatments were conducted from reproductive stage R1 to R5 or from R5 to R7 by applying the nutrient solution with different nitrogen concentrations. The high nitrogen concentration from R1 to R5 delayed the decline in SPAD value and leaf nitrogen concentration and improved the seed yield performance in Sachiyutaka, whereas stimulated the decline in SPAD value and leaf nitrogen concentration and had no effect on seed yield in Tamahomare. However, high nitrogen concenntration during R5 to R7 delayed the decline in SPAD value and leaf nitrogen concentration and improved the yield performance more significantly in Tamahomare than in Sachiyutaka. The large seed yield increase by nitrogen enrichment during R5 to R7 in Tamahomare could be caused by both the high photosynthetic rate and vigorous nitrogen uptake during seed filling. These results suggested that the most effective timing of nitrogen enrichment during the reproductive growth period to increase seed yield varies with the cultivar due to the difference in the pattern of nitrogen assimilation.

Varietal Difference in Early Vegetative Growth during Seedling Stage in Soybean

Abstract Rapid development after emergence is important for seedling establishment and early vegetative growth, especially at a low planting density or inferior environmental conditions. This study was conducted to understand the varietal difference in the growth parameters during the seedling stage in soybean. Twenty-seven soybean varieties originating from six countries were examined in 2009 and 2010. The pots were arranged in a completely random block design with 5 replications (10 pots per variety), and the seedlings were sampled at 14 and 28 days after sowing (DAS). The shoot dry weight at 14 and 28 DAS was highly correlated with seed size, cotyledon digestion, and leaf area. However, no positive correlation was found between shoot dry weight and photosynthetic rate at 28 DAS. Chamame, a Japanese cultivar, with the largest seed size grew rapidly, and showed the heaviest shoot dry weight, greatest cotyledon digestion, fast leaf expansion and high photosynthetic rate. However, Moyashimame, a medium-seed-size cultivar, also grew rapidly with a high photosynthetic rate. Some varieties such as Tachinagaha (Japan), Hefeng (China), Parana and Pérola (Brazil), had a large or medium seed size, and high photosynthetic rate but showed a relatively small leaf area and light shoot dry weight. These results suggested that big seeds with rapid cotyledon digestion developed a wider leaf area and therefore large dry matter production, indicating that the conversion of stored energy was more important than the leaf photosynthetic activity for early growth.