去葉處理與栽植密度對大粒型水稻品種產量表現的影響

Abstract

為探討藉密植栽培增加大粒型水稻單位面積穗數以提高產量的可能性，及於抽穗期與抽穗後一週去除50 %葉片，以明瞭穀粒充實期間光合成物質的供需平衡關係，本試驗採用大粒型水稻品種Pegonil 與中粒型品種臺農67 號為材料，於抽穗後定期測定乾物質之累積與分佈，分析植株各器官全氮與非構造性碳水化合物（TNC）濃度的變化，並解析與產量表現間的關係。在第二期作的栽培環境下，臺農67 號較Pegonil 品種高產40%，穎花數與穗數為導致差異的主要產量構成因素。於抽穗期去除50%葉片，對成熟期Pegonil 穗重並無影響，但使臺農67 號穗重減輕32%，抽穗後一週去葉使兩品種穗重分別降低14%與32%；去除部份葉片使穗部氮濃度降低，但對葉片與莖稈氮濃度的影響甚小，亦即氮素再轉移至穗部之量甚微，此一現象與同一時期莖稈TNC 濃度大幅下降，顯示可能因光合成物質供應不足而降低根部活性，致使氮素供應不敷穀粒充實之需。密植栽培（行株距30 × 7.5 cm）較一般栽培（行株距30 × 15cm）可提高Pegonil 產量42%，唯仍較臺農67 號低產20%；密植使單株穗數減少，但大幅增加單位面積穗數，且不影響其他產量構成要素的表現，顯示改良栽培方法以提高大粒型水稻產量的可行性。高族群密度亦使穀粒氮濃度下降，在植株氮素供需與光合成物質的影響方面，可能與去葉處理具有相似的作用機制。本試驗中大粒型品種在抽穗後3 週內，單穗乾物質、全氮與TNC 的累積速率均顯著超過臺農67 號，為可資利用之優良生理特性，但穀粒充實期較短，穗內穎花累積TNC 之均一性差距頗大，易導致產量效率（yield efficiency）之降低。 Studies were conducted to examine the possibility of enhancing grain yield of a large-grain variety, Pegonil, through increasing panicle number per unit area by dense planting(30×7.5cm vs. 30×l5cm). Fifty percent leaf-cutting was also executed at either heading or 1 week after heading to investigate whether photosynthetic production was high enough to meet the needs of developing grains. Under the environmental conditions of the 2nd crop season, yield was 40% lower for Pegonil than for Tainung 67, a medium-grain variety, due mainly to fewer spikelet number per panicle and panicle number per hill. Leaf-removal at heading stage showed no effect on the mature panicle weight per hill, whereas a 32% reduction was observed in Tainung 67. Leaf-removal at 1 week after heading decreased panicle weight by 14% and 32%, repectively, for Pegonil and Tainung 67. Leaf-cutting caused a decrease of N concentration in the panicle, but not in the leaf blade and culm; indicating retranslocation of N to the panicle was insignificant. This, along with the low TNC concentration in the culm, suggested that photosynthetic production was unable to sustain high root activity, and hence the supply of N was not in an adequate state for the developing grains. Dense planting increased yield of Pegonil by 42%, which was still 20 % lower than the yield of Tainung 67. As panicle number per unit area was increased significantly while the other three yield components were unaffected, it indicated that grain yield of large-grain rice varieties could be increased substantially through cultural improvement. The large-grain variety Peganil possessed high accumulation rates of dry matter, N ane TNC in the panicles during the first 3 weeks after heading. However, shorter effective grain-filling period and less uniform TNC deposition among spikelets within a panicle resulted in lower yield efficiency of Pegonil. Improvement should be made before the large-grain rice varieties were able to be grown commercially.