Synopsis Defoliation caused reduction in all measures of yield. Severe, 80%, depodding reduced seed yield but increased weight per seed and stem yield. Moderate depodding, up to 40%, increased seed weight enough to maintain seed yield. Eighty percent depodding increased sugars, starch, and nitrogen in leaves and stems. Eighty percent defoliation increased the iodine number of seed oil, but decreased the oil and protein in seeds. Depodding increased seed protein but decreased the oil content and iodine number.
IntroductionThis study was initiated to determine the quantitative relationships between the various reserve constituents in soybean seeds as they are used by the developing seedling, and the effect of removal of the food supply contained in the cotyledons on subsequent growth of the plants. Many investigations have dealt with the transformations which occur in the reserve food materials in seeds of crop plants as germination proceeds. Few studies, however, have been concerned with the rate of transfer of these foods to the seedling. No reports have been found in the literature on how long the seedling is dependent on the reserves in the cotyledons for successful establishment and later development. This information was desired for use in mineral nutrition studies on soybeans particularly where the effects of limiting levels of some of the major nutrients are being investigated. At starvation levels of nutrition, it was felt that the amount of a particular element supplied by the cotyledons may be sufficient to influence experimental procedure.Using semiquantitative, microchemical methods on freezing microtome sections of Manchu soybean seeds, VON OHLEN (12) followed the translocation of organic and inorganic substances from the cotyledons to the seedling during germination in the dark. His results show that oil moved out of the cotyledons more rapidly than the other main organic reserve, protein, and that among the mineral elements, potassium was translocated at a greater rate than phosphorus or magnesium. HOLMAN (7) found that the fat content of Agat(e) soybeans had decreased 78%, 17 days after planting. The work of MILLER (10) on sunflower probably gives the most complete data on the transformation and movement of foods in oilseed plants. The seedling material analyzed was grown under greenhouse conditions with natural light but at emergence the seedlings were transferred to a carbon dioxide-free atmosphere so that the seedlings were dependent upon the reserves of the cotyledons throughout the growing period. Miller's data show that hydration of the cotyledons was complete in 10 days, dry weight decreased gradu-
SummarySoybean samples containing a large proportion of damaged seed were separated into sound and damaged portions and these portions were then analyzed chemically.Analysis of these samples indicated that damage to the seed caused considerable variation in percentages of oil, protein, ash, and in iodine number and acid of the oil. Sugars in the damaged portions of the soybean samples were generally low when compared with the sound portions.Weather damaging of soybean seed caused a marked increase in percentage of crude protein. Oil percentages were sometimes higher and sometimes lower in the damaged portions. The iodine number of the oil was usually but slightly affected, and the acid number was higher in the damaged portions.In order that the chemical analysis of the samples may be representative of the true composition of a strain, the seed analyzed should be of good quality and contain no more than a small proportion of damaged seed.
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