The Relationship between Respiration and the Seed Growth during Ripening Period in Soybean.

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Respiration rates of pods with seeds in soybean at 24ﾟC were almost the same throughout their ripening period. Q10 values of respiration rate to temperature were also constant at around 1.8 during ripening period. Q10 values of pods and that of seeds were almost the same. When the color of pod began to brown, respiration rate of pods with seeds suddenly decreased, and within one or two days it could not be detectable.The growth rates of seeds for three years from 1992 to 1994 were not different irrespective of the big difference of weather conditions. The storage matters in seed, oil and protein, accumulated almost the same manner with dry matter accumulation. Oil and protein stopped to accumulate after the onset of pod yellowing. Therefore, the stop of the storage matter accumulation and respiration was the result of fully ripening, and not the cause of that.The difference between year to year was big in sugar, starch and methanol soluble nitrogen compounds in seeds. Especially, the sugar content at the onset of pod yellowing showed big difference yearly, almost zero in 1992 and very high in 1993. Starch content was high at the middle of ripening stage and decreased after that, irrespective of sugar content. Therefore, sugar content did not always related to the stop of seed growth, but starch content or breakdown could relate to it. Methanol soluble nitrogen compound content in seeds was very low and that of pods was assumed to be important to the growth of seeds. This content in pods decreased with ripening of seed, but decreasing rate was different yearly. The late decreasing rate was accompanied by late maturity and high dry matter accumulation in seeds.It was concluded that the metabolism of sugars, starch and methanol soluble nitrogen compounds could relate to the factors to determine the time of maturation, fully ripening.