초록
IR667의 낮은 등숙률요인(登熟率要因)을 밝히고자 재식밀도(栽植密度)와 질소수준(窒素水準)만을 달리하여 $5m^2$시멘트 pot IR667-수원(水原) 214와 진흥(振興)을 재배(栽培)하여 등숙구조(登熟構造)와 이의 생리적(生理的) 기능(機能)을 비교검토(比較檢討)하여 다음 결과(結果)를 얻었다. 1. IR667의 등숙률(登熟率)은 64로 진흥(振興)의 85보다 훨씬 낮으나 수량(收量)은 IR667이 790kg/10a로 진흥(振興)의 760kg보다 높았다. 2. 출수후(出穗後) 10일(日)의 NAR당(當) 등숙립수(登熟粒數)가 IR667은 6,490으로 진흥(振興)의 6,360보다 약간커서 IR667의 천립중(千粒重)은 29.9로 진흥(振興)의 31.2보다 적으며 NAR당(當) 총립수(總粒數)는 IR667이 10,530으로 진흥(振興)의 7,290보다 훨씬 높아 이것이 IR667의 등숙률(登熟率)이 낮은 요인(要因)이었다. 3. 투광상수(透光常數)는 IR667이 0.115로 진흥(振興)의 0.200보다 적어서 IR667이 보다 큰 등숙구조(登熟構造)를 갖게되는 장점(長點)을 보였다. 4. LAI 증가(增加)에 따른 LAI당(當) 입수(粒數)의 감소율(減少率)은 두 품종(品種)이 같았다. 5. 기초생산속도(基礎生産速度)(CGR)가 최고치(最高値)인 감계엽면적지수(監界葉面積指數)(critical leaf area index)는 IR667은 6.5이고 진흥(振興)은 5.2이며 5.2이하(以下)에서 진흥(振興)의 NAR이 IR667 보다 크다. 6. 최고수량(最高收量)을 얻을수 있는 출수기(出穗期) 최적엽면적지수(最適葉面積指數)(optimum leaf area index)는 IR667이 7.4로 진흥(振興)의 6.2보다 컸다. 출수기(出穗期) 평균엽면적지수(平均葉面積指數)는 IR667이 6.2 진흥(振興)이 4.7로 최적엽면적지수(最適葉面積指數)에 미달(未達)일 뿐 아니라 감계엽면적지수(監界葉面積指數)보다도 적었다. 7. 출당후(出糖後) 20일간(日間) LAI의 감소율(減少率)은 IR667이 크나 광합성량(光合成量)의 감소율(減少率)은 진흥(振興)이 컷다. 8. LAI가 클수록 NAR이 감소(減少)하는데 그 감소율(減少率)은 등숙(登熟)이 진행(進行)됨에 따라 진흥(振興)에서는 감소(減少)하나 IR677에서는 증가(增加) 함은 저온(低溫)에 의(依)한 광합성능(光合成能)의 저하(低下)와 호흡소모(呼吸消耗)에 기인(基因)하며 등숙적온(登熟適溫)이 IR667에서 높다는 것을 의미(意味)한다. 9. 수량(收量)-등숙률곡선(登熟率曲線)은 IR677이 진흥(振興)보다 등숙(登熟)이 수량(收量)에 미치는 영향이 적은 것으로 나타났고 이는 등숙환경(특히 기온)이 IR667에 부적(不適)한 때문으로 등숙환경(登熟環境)개선은 IR667의 최대 증수요인임을 보였다.
A local rice variety, Jinheung and newly bred IR667-Suwon 214 were grown in $5m^2$ concret pot with two spacings and two nitrogen levels and their ripening structure and its function were comparatively investigated to elucidate the causes of unusually low ripened grain ratio of IR667 lines. The following differences between two varieties were found. 1. Though IR667 had much lower ripened grain ratio (64%) than Jinheung (85%) grain yield(790 kg/10a) of IR667 was higher than that (760 kg/10a) of Jinheung. 2. Number of ripined grain per net assimiration rate (NAR) at 10 days after heading was a little higher in IR667 (6,490) than in Jinheung (6,360) consiting to lower grain weight ($29.9{\times}10^{-3}g$) in IR667 than $31.2{\times}10^{-3}g$ of Jinheung. But number of total grain per NAR was much higher (10,530) in IR667 than 7,290 of Jinheung indicating that it was the probable cause of low ripened grain ratio of IR667. 3. Extinction coeificient (K) was 0.115 in IR667 and 0.200 in Jinheung, thus IR667 could construct greater ripening structure per unit area. 4. Number of grain per LAI was decreased with increasing LAI at heading and the decreasing rate was similar for both IR667 and Jinheung. 5. Critical leaf area index at which crop growth rata (CGR) is maximum was 6.5 for IR667 and 5.2 for Jinheung. Below 5.2 of LAI net assimilation rate was always higher an Jinheung throughout the growing season. 6. The estimated optimum leaf area index having maximum grain yield was 7.4 for IR667 and 6.2 for Jinheung at 10 days after heading. However, actual leaf area index was 6.2 for IR-667 and 4.7 for Jinheung and these were even below critical leaf area index. 7. The decrease of LAI during ripening period was great in IR667 but photosynthesis per $m^2$ was decreased more rapidly in Jinheung. 8. Net assimilation rate (NAR) decreased with the increase of LAI at any time of ripening period. The decreasing rate of NAR with the increase of LAI was greater in IR667 with ripening. The greater decreasing rate of NAR in IR667 seemed to be attributed to low photosynthetic activity and high respiratory loss due to the requirement of higher optimum temperature of ripening. 9. Grain yield-ripened grain ratio curve showed less contribution of dry matter yield after heading to grain yield in IR667 than in Jinheung due to unfavorable ripening environment(specialy air temperature) indicating that yield of IR667 could most effectively increased through the improvement of ripening environment.