Yoshida - 1981 - Fundamentals of Rice Crop Science

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RICE PLANT CHARACTERS IN RELATION TO YIELDING ABILITY 223 growth before reproductive growth starts, provided there is no interruption. Thus, the total growth duration of early maturing varieties is about 90 days. Directseeding appears essential for a 90-day variety to have sufficient vegetative growth before panicle initiation. For transplanted rice with a total duration of 90 days, 20 days in the seedbed and 60 days for reproductive growth and ripening leave only 10 days for active vegetative growth, which is not sufficient. About 100 days is the shortest duration for achieving reasonably high yields with transplanted rice. In the comparison above, the number of field days is 10 days shorter for a 100-day variety in transplanted rice than for a 90-day variety in direct-seeded rice (Yoshida 1978). Among the materials now available, IR747B2-6 is one of the best early maturing lines in the tropics; it matures in 95–98 days (Table 6.4). IR36 matures in 105 days. Thus, attempts to shorten growth duration are approaching the limit for the shortest possible growth duration with high yielding potential. 6.5. ASSOCIATION BETWEEN PLANT CHARACTERS Conceptually, each plant character could be independent; factually, several plant characters are often closely associated. 6.5.1. Foliar absorption coefficient and plant characters The foliar absorption coefficient (k) is related to light penetration into a plant canopy by equation 5.8: I In = –kF I O The foliar absorption coefficient is negatively correlated with specific leaf area and the average leaf angle of the upper three leaves when measured from the horizontal plane and weighted for the area of each leaf (Table 6.5). Culm length is negatively correlated with the average leaf angle of the upper three leaves. As a consequence, the culm length is positively correlated with the Table 6.5. Correlation between foliar absorption coefficient and some plant characteristics. a Plant characteristic Correlation coefficient Culm length +0.549** Crop ht +0.130 Number of culms -0.021 Mean area of single leaf -0.244 Specific leaf area -0.544** Leaf angle Leaf angle × specific leaf area -0.539** -0.717** a Hayashi and Ito (1962).
224 FUNDAMENTALS OF RICE CROP SCIENCE 6.6. Relationship between plant height and harvest index (Tanaka et al 1966). foliar absorption coefficient. The specific leaf area (cm/g) is a measure of leaf thickness, and varies with variety, leaf position, growth stage, nutrition, and climatic environment (Murata 1975). Values of specific leaf area for rice varieties range from about 200 to 450 cm 2 /g. The foliar absorption coefficient is negatively correlated with specific leaf area, which differs from Tsunoda’s conclusions (1964). 6.5.2. Plant height vs harvest index vs nitrogen responsiveness Harvest index is inversely correlated with plant height (Fig. 6.6). Thus, tall varieties usually have low harvest indices (or low grain-straw ratios). The grainstraw ratio of 5 highly nitrogen-responsive varieties ranged from 0.95 to 1.23 and Table 6.6. Grain-straw ratios for selected varieties. a Grain-straw Class Variety ratio Highly nitrogen IR8 1.15 responsive Chianung 242 1.14 Taichung Native 1 1.20 Tainan 3 1.23 IR5 0.95 Mean 1.13 Low or negatively Hung 0.60 responsive to Peta 0.60 nitrogen Nahng Mong S4 0.49 Puang Nahk 16 0.40 H-4 0.58 Sigadis 0.69 Mean 0.56 a Chandler (1969).
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FOREWORD Rice is vital to more than
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CONTENTS Foreword Preface GROWTH AN
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3.2. Adaptation to Submerged Soils
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4.5. Corrective Measures for Nutrit
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1 .1. OUTLINE OF THE LIFE HISTORY T
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GROWTH AND DEVELOPMENT OF THE RICE
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Page 203 and 204: 5.1. PHOTOSYNTHESIS 5.1.1. Photosyn
Page 205 and 206: PHOTOSYNTHESIS AND RESPIRATION 197
Page 207 and 208: Photosynthetic characteristics Meas
Page 223 and 224: A traditional tall variety vs an im
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Page 257 and 258: Table 7.6. An example of high yield
Page 261 and 262: REFERENCES AGRICULTURAL POLICY STUD
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Yoshida - 1981 - Fundamentals of Rice Crop Science

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