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Articles by Qi-Rong SHEN
Total Records ( 4 ) for Qi-Rong SHEN
  Ying-Hua DUAN , Xiao-Ming YIN , Ya-Li ZHANG and Qi-Rong SHEN
  Rice is being increasingly cultivated in intermittently irrigated regions and also in aerobic soil in which Nitrate (NO3) plays important role in nutrition of plant. However, there is no information regarding the influence of nitrate on the overall growth and uptake of nitrogen (N) in rice plant. Solution culture experiments were carried out to study the effects of NO3 on the plant growth, uptake of N, and uptake kinetics of NH+4 in four typical rice (Oryza sativa L.) cultivars (conventional indica, conventional japonica, hybrid indica, and hybrid japonica), and on plasma membrane potential in roots of two conventional rice cultivars (indica and japonica) at the seedling stage. The results obtained indicated that a ratio of 50/50 NH+4 -N/NO3-N increased the average biomass of rice shoots and roots by 20% when compared with that of 100/0 NH+4 -N/NO3-N. In case of the 50/50 ratio, as compared with the 100/0 ratio, total N accumulated in shoots and roots of rice increased on an average by 42% and 57%, respectively. Conventional indica responds to NO3more than any other cultivars that were tested. The NO3supply increased the maximum uptake rate (Vmax) of NH+4 by rice but did not show any effect on the apparent Michaelis-Menten constant (Km) value, with the average value of Vmax for NH+4 among the four cultivars being increased by 31.5% in comparison with those in the absence of NO3. This suggested that NO3 significantly increased the numbers of the ammonium transporters. However, the lack of effect on the Km value also suggested that the presence of NO3had no effect on the affnity of the transporters for NH+4. The plasma membrane potential in the roots of conventional indica and japonica were greatly increased by the addition of NO3, suggesting that NO3could improve the uptake of N by roots of the rice plant. In conclusion, the mechanisms by which NO3enhances the growth and N uptake of rice plant was found by the increased value of Vmax of NH+4 and increased plasma membrane potential. Thus promotion of nitrification in paddy soil is of great significance for improving the production of rice.
  Yao-Hong ZHANG , Jian-Bo FAN , Ya-Li ZHANG , Dong-Sheng WANG , Qi-Wei HUANG and Qi-Rong SHEN
  Developing high-yielding rice (Oryza sativa L.) cultivars depends on having a better understanding of nitrogen (N) accumulation and translocation to the ear during the reproductive stage. Field experiments were carried out to evaluate the genetic variation for N accumulation and translocation in different Japonica rice cultivars at different N rates and to identify any relationship to grain yield in southeast China. Four Japonica cultivars with similar agronomic characteristics were grown at two experimental sites in 2004 with three N rates of 0, 60, and 180 kg N ha−1. Dry weights and N contents of rice plants were measured at tillering, initiation, anthesis, and maturity. Grain yields exhibited significant differences (P < 0.05) among the cultivars and N application rates. Increasing N rates improved N uptake at anthesis and maturity in all four cultivars (P < 0.05). N translocation from vegetative organs to the grains increased with enhanced N rates (P < 0.05). N translocation to the grains ranged from 9 to 64 kg N ha−1 and N-translocation effciency from 33% to 68%. Grain yield was linear to N uptake at anthesis (r2 = 0.78**) and N translocation (r2 = 0.67**). Thus, cultivars with a high N uptake at anthesis, low residual N in the straw at maturity, and appropriate low N fertilizer supply in southeast China should effciently increase N-recovery rate while maintaining grain yield and soil fertility.
  Bo WANG , Tao LAI , Qi-Wei HUANG , Xing-Ming YANG and Qi-Rong SHEN
  Endogenous hormones play an important role in the growth and development of roots. The objective of this research was to study the effect of four types of N fertilizers on the root growth of strawberry (Fragaria ananassa Duchesne) and the endogenous enzymes of indole-3-acetic acid (IAA), abscisic acid (ABA), and isopentenyl adenosine (iPA) in its roots and leaves using enzyme-linked immunosorbent assay. Application of all types of N fertilizers significantly depressed (P ≤ 0.05) root growth at 20 d after transplanting. Application of organic-inorganic fertilizer (OIF) as basal fertilizer had a significant negative effect (P ≤0.05) on root growth. The application of OIF and urea lowered the lateral root frequency in strawberry plants at 60 d (P ≤0.05) compared with the application of two organic fertilizers (OFA and OFB) and the control (CK). With the fertilizer treatments, there were the same concentrations of IAA and ABA in both roots and leaves at the initial growth stage (20 d), lower levels of IAA and ABA at the later stage (60 d), and higher iPA levels at all seedling stages as compared to those of CK. Thus, changes in the concentrations of endogenous phytohormones in strawberry plants could be responsible for the morphological changes of roots due to fertilization.
  Jian-Bo Fan , Ya-Li Zhang , D. Turner , Yin-Hua Duan , Dong-Sheng Wang and Qi-Rong Shen
  The variation in nitrogen (N) uptake by rice has been widely studied but differences in rice root morphology that may contribute to this variation are not completely understood. Field and greenhouse experiments were carried out to study N accumulation, root dry weights, total root lengths, root surface areas, and root bleeding rates of two rice cultivars, Elio with low N-use efficiency and Nanguang with high N-use efficiency. Low (1 mmol N L−1) and high (5 mmol N L−1)N applications were established in the greenhouse experiment, and the N rates were 0, 120, and 240 kg ha−1 in the field experiments at Jiangning and Jiangpu farms, Nanjing, China. The results showed that the N accumulation, root dry weight, total root length, and root surface area increased with an increase in N application. At the heading stage, N accumulation in the shoots and roots of Nanguang was greater than that of Elio in the field experiments and that of Elio at 5 mmol N L−1 in the greenhouse experiment. After the heading stage, N accumulation was higher for Nanguang at both 1 and 5 mmol N L−1 in the greenhouse experiment. The total root length and root surface area were significantly different between the two cultivars. Over the range of the fertilizer application rates, the root lengths of Nanguang at Jiangning Farm were 49%–61% greater at booting and 26%–39% greater at heading than those of Elio, and at Jiangpu Farm they were 22%–42% and 26%–38% greater, respectively. Nanguang had a greater root bleeding rate than Elio. It was concluded that the N-use efficiency of the two rice cultivars studied depended to a great extent on the root morphological parameters and root physiological characteristics at different growth stages.
 
 
 
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