| Budget Amount *help |
¥3,750,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥150,000)
Fiscal Year 2007: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2006: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2005: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
Dark-respiration is a physiological process which supplies essential energy for growth and maintenance in crop plants. It is necessary to clarify the relationship between dark-respiration and dry-matter production quantitatively. Ten crop species were cultivated in the upland or paddy field, and the growth parameters (CGR ; crop growth rate, NAR ; net assimilation rate and LAI ; mean leaf area index) and the dark-respiration rates were measured during the whole growth season. CGR in each crop stands increased with the growth, and showed the maximum at the beginning of reproductive period followed by the gradual decrease until the physiological maturity. Specific respiration rate (Rs) of whole plant showed the maximum at the earlier stage of the vegetative growth, and rapidly decreased until the beginning of reproductive period, after that almost constant during the ripening period. Rs in the vegetative organs (leaf blade and stem) changed almost same tendency with that in the whole pla
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nt, and Rs in the leaf blade was higher than that in the stem during the reproductive period. Rs in the sink organ (panicle, pod and flower, etc.) showed the maximum at the earlier seed growth period followed by the rapid decrease, and was similar value or lower than that in the vegetative organ at the physiological maturity. Nitrogen content in the sink organ was highest at the beginning of seed growth followed by rapid decrease, and re-increased at the later ripening period in sunflower, soybean, kenaf and groundnut, of which seed contained much protein. Growth efficiency (GE=CGR/ (CGR+Rp), Rp ; per plant respiration rate) in the whole plant during the vegetative period was more than 60% in corn, sunflower, kenaf and barley, and lower in potato, soybean and groundnut showing 39-55% due to the higher Rp. GE in the whole plant during the reproductive period was smaller than that during the vegetative period (except potato) related to the increase in the maintenance respiration of nonassimilative organ and the decrease in the thy-weight of vegetative organs due to translocation of assimirates. Close correlation was found between the GE in the sink organ, which occupied larger portion of the phytomass at the later stage of ripening period, and the oil content of reserve material in the sink organ indicating that the cost of respiration used for oil synthesis was larger than the other substances. It was speculated that the variation in GE among crop species was due to the differences in the cost of growth and maintenance respiration of vegetative organs and of synthesis used for the reserve substances. Less
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