Physiological Studies of Rice Tillers II. Productivity of Varieties Differing in Grain Volume

Abstract

Amount of dry matter, total nitrogen and total nonstructural carbohydrates (TNC) in the leaf blades, leaf sheaths and stems from various node positions, as well as panicles, of rice tillers were analyzed at stages of grain development. The purpose of this study was to compare the potential of productivity between a large-grain variety Mira and a medium-grain variety Tainung No. 67. Nitrogen concentrations in various organs of Mira tillers were significantly higher, whereas TNC concentrations were lower, than those of Tainung No. 67 tillers. When compared to Mira on a per tiller basis, Tainung No. 67 produced 14-55% less dry matter and 36-39% less TNC during the test period. For a mature panicle from a single tiller, the amounts of dry matter and TNC accumulated by Tainung No. 67 were only 61-74% and 63-80%, respectively, of those accumulated by Mira. Those results indicated that the productivity per tiller was greater for the large-grain variety. As panicle number per hill was very low for Mira, community productivity was 50% higher for Tainung No. 67 in the first crop hut was comparable between varieties in the second crop. No difference in the increase rates of major components in panicles was found between varieties, indicating the absolute amount of translocation into panicles was greater for Mira. Results suggested that yield increase through enlarging grain size was possible. However, responses of the large-grain rice to the environmental factors should be further understood. 以大粒種水稻品種 Mira （千粒重約 379 ）及中粒型水稻品種臺農 67 號（千粒重約 25g ）為材料，自抽穗起每週以分蘗為單位取樣，測定源自不同節位之葉片、葉鞘、莖及穗部的乾物重，全氮及非構造性碳水化合物（ TNC ）含量的變化，目的在比較兩型水稻的生產能力。試驗結果發現 Mira 各器官內之全氮濃度顯著較臺農 67 號為高，每一分蘗吸收的氮量亦超出臺農 67 號 40 %以上。在穀粒充實過程的淨乾物質與 TNC 生成量比較，如以單一分蘗為單位，臺農 67 號分別較 Mira 少 14-55 %與 36-39 % ；成熟期時，臺農 67 號水稻之單一穗重僅為 Mira 之 61-74 % ，單一穗內 TNC 含量僅為 63-80 % ，顯示大粒型水稻單一分蘗的生產力較高，而推廣品種亦有再加改良的可能。由於大粒型水稻的穗數太少，故就群落生產力而言，一期作臺農 67 號較 Mira 高 50 %，二期作則兩品種相似，即 Mira 在第二期作有較優良的表現。兩品種穗部主要成份的累積速率相當，表示絕對轉流量以大粒型品種為高。本試驗結果建議，經由增大穀粒體積謀求稻作增產或有可能，但較大粒型水稻品種（系）對各項環境因子一諸如溫度，栽植密度、氮需要量等之反應，仍應先加以深入的瞭解。