The pulsed NMR technique for rapid and nondestructive determination of oil in oilseeds has been developed. The effects of spin‐lattice relaxation time, spin‐spin relaxation time, seed moisture, angular position of the seeds, sample tube thickness, and sample height upon the magnitude and reproducibility of the NMR signal were studied. Based upon these studies, various parameters for seed oil analysis have been fixed. The oil content of Brassica, peanut, and sunflower seeds was determined. The reproducibility of the measurement is ± 1 %. The technique was tested by measuring the oil content of the same seeds by the cold percolation method (CCl4 extraction). It was further tested by determining the oil content of 60 Brassica seed samples independently at three laboratories. The results of these tests are given.

Pulsed nuclear magnetic resonance (NMR), which takes about 10 sec per analysis, has been used for rapid nondestructive determination of oil in oilseeds without weighing and oven drying the seeds. This has been done by measuring the free induction decay (FID) signal of solid and liquid in oilseeds. The oil values determined by this method for mustard, sunflower, and soybean seeds have been compared with the values determined by measuring the oil signal alone in the intact seeds, which takes about 2 min per analysis. Correlation for mustard is 0.988, for sunflower 0.945, and for soybean 0.931. The reasons for better agreement for mustard and the way of improving it for sunflower and soybean have been discussed.

Pot culture studies were conducted using two drought-tolerant and one susceptible cultivar of wheat (Triticum aestivum L.) under three different moisture regimes. Proton spin-lattice relaxation time, Ti, leaf water content, LWC, leaf water potential, i|i, solute potential, i|is and turgor potential, ifip were measured from 45 to 75 d after sowing at weekly intervals. The three cultivars did not differ significantly in their values of LWC, leaf water potential, and their components in the stressed and unstressed plants; but they did difTer significantly in their Ti values both under stressed and unstressed conditions on all days of measurement, with the drought tolerant cultivars having a higher T\ compared to the susceptible cultivar. This suggests that leaf water T^ is a better parameter for describing plant water status than the traditional water relation indices. The relation between i f/ and Tl was logarithmic, indicating the similarity between Ti and water activity of the cellular water.

The free induction decay (FID) and echo signals in a spin‐echo pulse sequence have been used for seed oil determination without weighing and drying the seeds with nuclear magnetic resonance (NMR) equipment that has a magnetic field of low homogeneity. Earlier known methods, based on use of the FID signal to determine seed oil, become inapplicable when the magnetic field homogeneity is poor, because the angular position of seed significantly affects the signal. The present method, which elegantly eliminates the angular dependence, involves sampling the FID signal at 10 µs after a 90° pulse and the subsequent echo signal at 100 µs formed by applying a 180° pulse at 50 µs. Such short pulse spacing in spin‐echo sequence produces almost a full oil signal. It also eliminates the effects of sample‐to‐sample variation inT2 and molecular diffusion on oil signal. The oil values obtained by this method are in good agreement (correlation for mustard: 0.952; linseed: 0.99; and for peanut: 0.912) with the values obtained by the well established and accurate pulsed NMR method, which is based on the measurement of the FID signal of oil in dried and weighed seeds.

The change in seed oil percentage and 100-seed weight of Brassica juncea Varuna was studied as the crop matured during rabi 1977-78. Statistically, the oil percentage reached its highest value at 55 days from flowering, whereas the 100-seed weight was highest about 20 days later, when the pods were fully yellow. Oil yield (the product of oil percentage and seed weight) also reached its highest value when the pods were fully yellow. This information should enable the crop to be harvested at the proper physiological stage (yellow-podded) for maximum oil yield.The importance of harvesting the mustard crop at the proper physiological stage to ensure maximum yield of oil can hardly be over-emphasized. Mustard growers are prone to harvest according to convenience, at less than optimal stages of maturity (Dasgupta, 1976), resulting in loss of either seed or oil. The present study was aimed at finding the physiological stage at which harvesting would result in maximum yield of oil, which depends on the product of seed-oil percentage and seed weight. MATERIALS AND METHODSBrassica juncea cv Varuna was sown on 8 October 1977 on the IARI farm, in rows 60 cm apart, thinned to 15 cm between plants. At and after flowering, six random plants were selected from amongst the population for taking pod samples at different maturity periods. Newly-opened flowers were tagged daily for the next 10 days, using coloured threads on each of the racemes of the six selected plants and different colours to distinguish the first days of flowering from each other. About 10-15 tagged pods were harvested at random from each of the six plants after 20, 25, 30, 33, 35, 40, 45, 50, 55, 65, 75 and 90 days from flowering. The oil percentage of each of these samples was determined by the pulsed NMR method, in which the seeds are first dried at 60 °C to eliminate the contribution of moisture from the oil signal (Tiwari et al., 1974). The oil percentage in the present studies is expressed on the basis of seeds dried at 60 °C, but the weights of 100-seeds, taken at random from each sample and dried at 60 °C, were also recorded. The colour of each pod was noted at the final stages of maturation that gave perceptible differences in the attributes studied, i.e. greenish yellow on the 65th day and fully yellow on the 75th day after flowering; by the 90th day most of the pods had become bone dry and brown. RESULTS AND DISCUSSIONIt had been earlier observed by the authors that there was a considerable intrapopulation (plant-to-plant) variation in oil content in Brassica juncea varieties 0014-4797/79/0000-1383 801.00

No abstract

SUMMARYOil content (percentage) was determined by pulsed nuclear magnetic spectrometry to study its variability in rai (Brassica juncea) and yellow sarson (B. campestris). Wide inter-varietal and intra-varietal variability was observed in both crops. Genetic aspects of oil content were also worked out, and single-plant and bulk selection methods used for 3 years to exploit the intra-varietal variability. A positive trend in the improvement of oil percentage was observed in 27 out of 30 varieties, some of which showed significant improvements over their respective unselected stocks. A maximum increment of 7% was observed in variety BR 40 of rai and 6% in variety YSM of yellow sarson.