| Summary: | 碩士 === 國立中興大學 === 農藝學研究所 === 78 ===
In order to realize the possibility of predicting the rice growth duration and developmental by using thermo unit accumulation, the field experiments were conducted by three rice cultivars TNG 67, TCS 10 and TC 190 in four transplanting dates at two locations in 1989. The thermo models used were the growing degree days(GDD) and modified growing degree days(HGDD), the GDD for a given day is defined as average of daily maximum and mininum temperature minus a base temperature for growth of 12.5℃ ,MGDD is the same equation as GDD but with a threshold of 30℃ imposed on maximum temperature. The base temperature was got by germination test.
The results indicated that the thermo unit models using the GDD and MGDD were more accurate than calendar days for predicting all rice growth stage except the reproductive stage. The MGDD accumulation index on rice growth and development at different growth seasons and locations showed the stable estimator than GDD.
In different transplanting, while thermo unit accumulated to a constant, the dynamic process of leaf area of rice cultivars were simultaneously got optimum, the thermo unit accumulated quickly in growth duration, total dry weight were decreased. With delay transplanting, yield were decreased significantly due to No. of spikelets per panicle cause high temperature.
Based on the temperature and growth relationships, the MGDD accuulated index on rice growth and development at different transplanting dates and locations, showed the most stable estimator than calendar days. Grain yield was postively with plant part of growth rate by using MGDD as divisor of whole rice growth stage and reproductive stage. Grain yields was also positively correlated with part of growth rate in this studies.
Therefore, the precision of the temperature function based on the MGDD would be extremely helpful for indentify the potential productivity at given environment and for developing the high yield rice genotype under specific temperature regime.
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