水稻臺農67號及其粒重型近同源系之光合物質與氮素供需關係比較

Abstract

本試驗採用中粒型水稻品種臺農67號（千粒重約25g）、大粒型品種Pegonil（千粒重40g以上）及四個以前者為輸迴親經回交五或六代並自交多次之臺農67號粒重型（千粒重約30─36g）近同源系為材料，在田間進行兩年四作試驗，比較抽穗至成熟期間之乾物質及氮素累積量，分析粒重效應對光合物質與氮素供需關係的影響。臺農67號的稻穀產量均高於Pegonil品種；經連續四作調查，回交後代的粒重穩定，部份之產量並與臺農67號相近，但未能超越。臺農67號抽穗後累積乾物量佔成熟期總乾物量之40％以上，在期作間頗為穩定；對Pegonil與回交品系而言，此一比值以第一期作較低，於期作內並與產量表現有正相關關係。抽穗後乾物生成量低於穀粒產量，亦即有顯著之再轉移現象。各品種及品系之收穫指數均在0.45以上，但基因型間之乾物分配效率仍有差異，以生產力較高之BC-6品系較低。大粒型品種Pegonil葉片、莖稈與穗部氮素濃度均顯著高於臺農67號，回交品系雖具粒重特性，但氮素濃度則與中粒型親本相同。穀粒充實期間水稻植株累積氮量佔總氮量之比例，平均以Pegonil最低，第二期作又顯著較第一期作為高；抽穗後累積氮量平均僅為穀粒氮含量之40％以下，亦即穀粒充實對營養器官氮素轉移具有極高的依賴性。本試驗結果顯示粒重型近同源系之氮素供需關係與其輪迴親臺農67號相似；另一方面，第一期作產量優於二期作，但對抽穗前預貯氮素的依賴度較高，其意義猶待探討。 The large-grain variety, Pegonil, medium-grain variety, Tainung 67 and four nearisogenic lines of the latter with higher 1,000-grain-weight (30－36g) were included for field experiments from the 1st crop of 1987 and the 2nd crop of 1988. Status of dry matter and N accumulation at heading and maturity was studied. The purpose was to analyze the differences in contribution parameters of post-heading accumulation to grain yield. Experimental results indicated that grain yield of Tainung 67 was consistently higher than that of Pegonil. Near-isogenic lines showed stability in their grain weight, with grain yield similar to but not higher than that of Tainung 67. Dry matter accumulated after heading of Tainung 67 accounted for 40% of total dry weight at matuity. and the ratio was stable across the four crop season tested. The ratio was lower for Pegonil variety and the near-isogenic lines and was positively correlated to grain yield within crop season. The fact that dry matter produced after heading was lower than grain yield indicated significant retranslocation of photosynthate from vegetative organs to the developing grains. Harvest indexes of all rice materials were above 0.45. However, differences among genotypes existed as BC-6 lines, which were high in dry matter production, were low in partition efficiency in diverting dry matter to the grains. N concentrations in the leaf blade, culm and grain were significantly higher for Pegonil than for Tainung 67. The near-isogenic lines, despits their higher grain-weight, were similar in N concentration to their recurrent parent Tainung 67. Amount of N acquired after heading (Na), and the ratio of Na to total N present at maturity (Nt), were lower for the1st than for the 2nd crop rice, and lower for Pegonil variety. In average, Na accounted for only 40% of the N present in the grain, which suggested the dependency of grain-filling on N accumulated before heading. In general, status of N assimilation and utilization by the four near-isogenic lines with higher grain-weight resembled to that of Tainung 67 with lighter grain-weight. The physiological explanation of the importance of N retranslocation to grain yield remained to be clarified.