Morphological and agronomic characteristics of different rice types
2001
Samson, M.I. | Siband, P. | Gapas, P.N. (International Rice Research Inst., Los Banos, Laguna (Philippines). Crop, Soil and Water Sciences Div.)
Comparison between a modern, high-yielding, irrigated rice variety (IR72) and some IRRI new plant types (NPT) showed that the latter's growth was oriented toward strong vegetative organs. In NPT, stems were stronger, leaves were thicker, and root diameter was larger. As a consequence, each gram of dry matter formed in NPT gave less leaf area and root length, thus limiting the interception for resources (solar radiation, soil nutrients). This led to a slower extension rate in space, a decrease in dry matter growth and nutrient demand rates, lower weed competitiveness, and a different nitrogen response. These morphological changes necessitate adjustment in cultivation practices. The basic relationships between tillering rate, stem vigor, leaf thickness, and root diameter were trends expressed through selection pressure, but these characteristics are not strictly linked. Tropical hybrids appeared to be selected more toward vigor rather than morphology only. The combined traits of hybrids - slightly slower tillering, higher stem vigor, thinner leaves - resulted in a growth rate similar to that of modern varieties, and a higher grain production per day relative to its growth duration
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