Yoshida - 1981 - Fundamentals of Rice Crop Science

More documents

Recommendations

Info

36 FUNDAMENTALS OF RICE CROP SCIENCE 1.34. Relative water absorption rate of different parts of a single rice root (Kawata and Lai 1968). As shown in Table 1.9, old roots took up about 60% of the water and nutrients absorbed by the plant. Even if water and nutrient uptake is expressed on a dry root weight basis, the capacity of the old roots is greater. This higher capacity may be partly attributed to the tissue’s low nutrient and high sugar content, which favor active nutrient uptake. The new roots, however, have a higher oxidizing capacity than the old roots. 1.7.5. Water and nutrient uptake by the root system Water shortages are frequently a limiting factor for crop growth in upland fields and in rainfed lowland fields. When water is supplied uniformly to all the soil profiles, the shallow layers are depleted of water first. Plants then take water from increasingly greater depths (Fig. 1.35). The rate of water absorption from a given soil volume is proportional Table 1.9. Absorption of water and nutrients by old and new roots. a Roots Amt. absorbed b Dry No. Max. H 2 O N P K wt root (ml) (mg) (mg) (mg) (g) length (cm) Old 1.75 157 33 155 14.0 4.5 9.8 (64) (62) (63) (63) New 1.32 175 25 86 8.5 2.5 5.7 (36) (38) (37) (37) Total 241 22.5 6.8 15.5 a Okajima (1962). b Figures in parentheses indicate percentages of the total.
GROWTH AND DEVELOPMENT OF THE RICE PLANT 37 1.35. Water extraction patterns after the irrigation on 21 Mar 1978 (IRRI 1979). to the effective total root length if other conditions are held constant (Gardner 1960, 1964). The high rate of water absorption results in a more rapid decrease in soil water potential in the shallow layers. Since the rate of water absorption is also proportional to soil water potential if other things are the same, the water absorption from the shallow layers will decrease. At this time, more water is available to the roots in the deeper soil profiles, and, hence, more water will be absorbed from these layers. In the mathematical model presented by Gardner (1960), the root was considered an infinitely long cylinder of uniform radius and water-absorbing properties. That is an approximation of the plant’s root and may not always apply to the real root. For greater accuracy, the root length should be corrected for root hairs and for degree of suberization. The total root length is also related to the plant’s capacity to absorb a nutrient. For corn plants grown in culture solution, the rate of phosphate uptake was proportional to the total root length (Jungk and Barber 1974). Thus, the capacity of the plant to absorb water and nutrients is closely related to the total length of the root system. 1.7.6. Measurement of root length and root density Measurement of total root length, even in a small sample, is difficult and tedious because roots can reach great lengths in even small volumes of soil. In 1966, Newman devised an elegant technique by which the total root length can be measured with relative ease. Newman’s method, as it is popularly used, uses a grid over which a root is randomly spread (Marsh 1971). Consider a grid with a total area of 14 × 14 cm 2 and with a regular distance of 14/11 cm between lines (Fig. 1.36). It is expected that the longer the root that is spread on the grid, the more intercepts it will make with the straight lines. Thus, the number of intercepts can be
Page 3 and 4: FOREWORD Rice is vital to more than
Page 5 and 6: CONTENTS Foreword Preface GROWTH AN
Page 7 and 8: 3.2. Adaptation to Submerged Soils
Page 9 and 10: 4.5. Corrective Measures for Nutrit
Page 11 and 12: 1 .1. OUTLINE OF THE LIFE HISTORY T
Page 13 and 14: GROWTH AND DEVELOPMENT OF THE RICE
Page 45: GROWTH AND DEVELOPMENT OF THE RICE
Page 75 and 76: 66 FUNDAMENTALS OF RICE CROP SCIENC
Page 97 and 98:
88 FUNDAMENTALS OF RICE CROP SCIENC
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
100 FUNDAMENTALS OF RICE CROP SCIEN
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186:
Page 187 and 188:
Page 189 and 190:
Page 191 and 192:
Page 193 and 194:
Page 195 and 196:
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
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 209 and 210:
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
Page 217 and 218:
Page 219 and 220:
Page 221 and 222:
Page 223 and 224:
A traditional tall variety vs an im
Page 225 and 226:
Page 227 and 228:
Page 229 and 230:
Page 231 and 232:
Page 233 and 234:
Page 235 and 236:
Page 237 and 238:
Page 239 and 240:
Page 241 and 242:
Page 243 and 244:
Page 245 and 246:
Page 247 and 248:
Page 249 and 250:
Page 251 and 252:
Page 253 and 254:
Page 255 and 256:
Page 257 and 258:
Table 7.6. An example of high yield
Page 259 and 260:
Page 261 and 262:
REFERENCES AGRICULTURAL POLICY STUD
Page 263 and 264:
Page 265 and 266:
Page 267 and 268:
Page 269 and 270:
Page 271 and 272:
Page 273 and 274:
Page 275 and 276:
Page 277 and 278:
show all

Yoshida - 1981 - Fundamentals of Rice Crop Science

Create successful ePaper yourself

Delete template?

Save as template?