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 หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Nodule Growth and Nitrogen Fixation of Selected Soybean Cultivars under Different Soil Water Regimes) ผู้เขียน: Aung Moe Myo Tint,  ดร.เอ็จ สโรบล, ศาสตราจารย์ , Sutkhet Nakasathein, Witith Chai-aree สื่อสิ่งพิมพ์:pdf AbstractSensitivity of N2 fixation to soil-drying has been considered as a major limiting factor to improving soybean yield. Seven soybean cultivars derived from various parents—namely, Nakhon Sawan 1 (NS-1), SJ.4, Sukhothai 1 (ST-1), Sukhothai 2, (ST-2), Sukhothai 3 (ST-3), Chiang Mai 60 (CM-60) and Chakkrabandhu 1 (CK-1) were evaluated for their nodulation and growth and yield in the first experiment. They were derived from various parents and their maturity differed from 90 to 110 d. Cultivars NS-1, ST-2 and ST-3 were selected to examine their nodule growth and N2 fixation capability under different water regimes in the second experiment. Nitrogenease activity (NA) of the nodulated roots of soybean increased with an increase in nodule dry matter (NDM) until 15 d after vegetative stage 4 (15 DAV4; R4) and then declined at 22 DAV4 (R5) under the well-watered regime. Under a water regime with progressive soil drying, the NA of the nodulated roots significantly decreased by 17.73% of the control from 7 DAV4 (R3). Among the soybean cultivars, NS-1 showed higher nodulation and N2 fixation capacity under both water regimes. The NA of nodulated roots severely diminished by 87.10% of control at 12 DAV4 (R4) under progressive soil drying and did not recover well after rewatering; nodule growth was similarly affected. There was a greater and significant correlation between NDM and other observed physiological parameters at the R4 stage. NDM is the most fundamental parameter for selecting better soybean cultivars for N2 fixation under both water regimes. The soil plant analysis development (SPAD:M-502) reading showed a highly significant correlation (r=0.84) with NA and other physiological parameters. SPAD readings could be used as a rapid assessment technique for the identification of potential cultivars with greater N2 fixation for both water regimes by measuring the accumulated total N in the shoot biomass at harvest. |
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หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Correlation between Pummelo Leaf Nitrogen Concentrations Determined by Combustion Method and Kjeldahl Method and their Relationship with SPAD Values from Portable Chlorophyl ผู้เขียน:Nopporn Jaroonchon, ดร.กฤษณา กฤษณพุกต์, รองศาสตราจารย์ , ดร.ลพ ภวภูตานนท์, ผู้ช่วยศาสตราจารย์ สื่อสิ่งพิมพ์:pdf AbstractDiscrepancies in reports of leaf tissue nitrogen (N) concentrations are in part due to different analytical methods among laboratories. Two standard methods of N determination, the combustion method and the Kjeldahl method, were compared for pummelo [Citrus maxima (Burm. f.) Merr.] leaf N analysis. Pummelo plants were fertilized with different N rates and leaves with different ages were sampled to obtain various leaf N levels. Leaf greenness (SPAD value) of each sample was measured by a portable chlorophyll meter prior to nitrogen analysis. The results showed that N concentrations of pummelo leaf samples were in the range 1.23-2.54% using the combustion method and 1.00-2.08% for the Kjeldahl method. The combustion method yielded higher N concentration values than the Kjeldahl method in every sample. A linear relationship between the combustion and Kjeldahl N values was highly significant (Kjeldahl N (%) = 0.7829 ? Combustion N (%) + 0.1150; R2 = 0.86 and p-value < 0.0001). The addition of samples of pummelo fruit parts that had wider ranges of N concentrations (0.74-4.08% for the combustion method and 0.57-3.51 % for the Kjeldahl method) than leaf tissue into the analysis increased the coefficient of determination (Kjeldahl N (%) = 0.8676 ? Combustion N (%) – 0.0384; R2 = 0.96 and p-value < 0.0001). Therefore, comparisons and interpretation of pummelo leaf N analysis results from different laboratories should mention the analytical method used and provide a linear equation for adjusting the N values. In addition, SPAD values had a positive correlation with leaf N concentrations determined by both methods and could be explained by quadratic polynomial equations (Combustion N (%) = 0.0003 ? SPAD2 – 0.0313 ? SPAD+2.5024; R2 = 0.21 and p-value < 0.0001; Kjeldahl N (%) = 0.0004 ? SPAD2 – 0.0372 ? SPAD+2.4086; R2 = 0.16 and p-value < 0.0001). It is suggested that the SPAD value determined by a portable chlorophyll meter can be used to obtain a quick estimation of pummelo leaf N status. |
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