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国立研究開発法人 国際農林水産業研究センター | JIRCAS

国名

フィリピン
Technical bulletin of the Tropical Agriculture Research Center

ISSN | 03889394 |
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書誌レコードID（総合目録DB） | AA00857848 |

本文フルテキスト

techtarc9-_1-72.pdf11.67 MB

In the studies on varietal differences of photosynthetic efficiency and dry matter production of *Indica* rice, the followings were clarified:

1) Measurement of net assimilation rate under the condition of isolated plants without mutual interferences was obtained by planting 10-20 seedlings per pot (Wagner pot with a size of a/2000) at the 2nd leaf stage, and by taking a half of the plants for the first sample at the 5th leaf stage, followed by the second sampling of remaining plants at the 7th leaf stage after a week.

2) Net assimilation rates of 301 varieties was measured under the such growing condition. The frequency distribution of net assimilation rate of varieties examined showed nearly a normal distribution, in which IR8 was located at about the middle point of the distribution. Range of the varietal differences of net assimilation rate as expressed by the ratio of the maximum value, to the minimum one and to the value of IR8 was 144-182 % and 122-147% respectively, with varieties grown under the same climatic environments. Furthermore, varietal differences of net assimilation rates were proved statistically with varieties examined more, in detail.

3) Net assimilation rate, of varieties measured at different climatic condition gave not only a significant correlation between NAR obtained under 2 different climatic conditions but also nearly equivalent heritability. Thus, net assimilation rate as a photosynthetic efficiency can be obtained irrespective of growth season either in the wet season or in the dry season of the tropics.

4) Net assimilation rate was closely associated with specific leaf weight determined with whole leaves out of many morphological plant characters. Specific leaf weight (SLW) was a stable character so that the order of varietal ranking with respect to specific leaf weight was not changed under different climatic environments. Total nitrogen content per unit leaf area was also closely associated with specific leaf weight. In the estimation of net assimilation rate from specific leaf weight, it was recognized that the latter can explain 52% of the, variation of net assimilation rate. Thus, specific leaf weight can be used as a primary index for selecting varieties with higher net assimilation rate. Furthermore, net assimilation rate can be estimated to an extent of 81 % by the multiple regression equation composed of plant characters such as leaf area per blade, tiller size, plant height, specific leaf weight, leaf area increase and increase of number of leaf.

5) Net assimilation rate of isolated plants at the maximum tiller stage showed the similar varietal difference as that in the early tillering stage. Also it was closely associated with specific leaf weight and total nitrogen content per unit leaf area. Thus, varietal characteristics with regard to net assimilation rate as a photosynthetic efficiency can be determined at an early growth stage, i.e., the 5th-7th leaf age of the early tillering stage.

6) It was clarified with the, statistical significance that there were varietal differences in net photosynthetic rate (P_{N}) in Indica rice, based on the measureemnt of CO_{2} exchange rate of intact single leaf. With 30 varieties examined, P_{N} ranged 43-54 mg dm^{-2}day^{-1} at the 5-6th leaf, 48-61 mg at the 6-7th leaf and 41-56 mg at the 9-l0th leaf. The coefficient of variation of P_{N} among varieties was at a range of 6.7-10.2%. Varietal order of P_{N} did not show a large deviation even among different growth stages.

7) Plant characters which have close positive relations to P_{N} were SLW, total nitrogen content per unit leaf area, plant height, dry weight increase and NAR. SLW and total nitrogen content per leaf area of a single leaf (which refers a fully-developed but not over-matured leaf, next to the topmost leaf) were closely associated with P_{N}. Varietal characteristic of SLW was expressed consistently with leaves of different leaf position. SLW and total nitrogen content per leaf area of a single leaf can be used as a criterion in the selection for higher P_{N}, because they are closely related to SLW and total nitrogen content per leaf area of whole leaves.

8) P_{N} which is regarded to express the maximum photosynthetic capacity was significantly associated with NAR which expresses a mean photosynthetic efficiency when both were measured at the same stage. NAR can be estimated from the multiple regression equation composed of variables; leaf area per blade, plant height, P_{N} and tiller size.

9) Net assimilation rate related positively to relative growth rate (RGR) and negatively to leaf area ratio among varieties. Namely, positive relation between NAR and RGR indicates that an increase of NAR is an important factor in increasing dry matter production.

10) Based on the analysis of the effect of varietal difference of leaf area and net photosynthetic rate to dry matter production, it was recognized that the partial contribution of net photosynthetic rate to dry matter production was nearly 30% whereas that of leaf area was nearly 70 % of the total dry matter production. Thus, under field conditions of plant population with leaf area below the critical leaf area index, any measures to increase their leaf area will be effective in increasing yields. Although the leaf area can be increased by increasing planting density and fertilizer application, the development of varieties which are characterized by large leaf area per unit dry weight, i.e., the varieties with small SLW that are able to increase their LAI at a low level of nitrogen supply is regarded as an useful approach for most of the present rice culture in Southeast Asian countries. On the other hand, the varietal improvement to increase photosynthetic efficiency may possibly be an important way to raise further grain yields with plant populations having leaf area index higher than the critical LAI.

11) From the above experimental results, 8 varieties of*Indica* rice that have very high NAR and P_{N} were selected. They may serve as the breeding material in developing new varieties with higher yielding potential than so far attained.

1) Measurement of net assimilation rate under the condition of isolated plants without mutual interferences was obtained by planting 10-20 seedlings per pot (Wagner pot with a size of a/2000) at the 2nd leaf stage, and by taking a half of the plants for the first sample at the 5th leaf stage, followed by the second sampling of remaining plants at the 7th leaf stage after a week.

2) Net assimilation rates of 301 varieties was measured under the such growing condition. The frequency distribution of net assimilation rate of varieties examined showed nearly a normal distribution, in which IR8 was located at about the middle point of the distribution. Range of the varietal differences of net assimilation rate as expressed by the ratio of the maximum value, to the minimum one and to the value of IR8 was 144-182 % and 122-147% respectively, with varieties grown under the same climatic environments. Furthermore, varietal differences of net assimilation rates were proved statistically with varieties examined more, in detail.

3) Net assimilation rate, of varieties measured at different climatic condition gave not only a significant correlation between NAR obtained under 2 different climatic conditions but also nearly equivalent heritability. Thus, net assimilation rate as a photosynthetic efficiency can be obtained irrespective of growth season either in the wet season or in the dry season of the tropics.

4) Net assimilation rate was closely associated with specific leaf weight determined with whole leaves out of many morphological plant characters. Specific leaf weight (SLW) was a stable character so that the order of varietal ranking with respect to specific leaf weight was not changed under different climatic environments. Total nitrogen content per unit leaf area was also closely associated with specific leaf weight. In the estimation of net assimilation rate from specific leaf weight, it was recognized that the latter can explain 52% of the, variation of net assimilation rate. Thus, specific leaf weight can be used as a primary index for selecting varieties with higher net assimilation rate. Furthermore, net assimilation rate can be estimated to an extent of 81 % by the multiple regression equation composed of plant characters such as leaf area per blade, tiller size, plant height, specific leaf weight, leaf area increase and increase of number of leaf.

5) Net assimilation rate of isolated plants at the maximum tiller stage showed the similar varietal difference as that in the early tillering stage. Also it was closely associated with specific leaf weight and total nitrogen content per unit leaf area. Thus, varietal characteristics with regard to net assimilation rate as a photosynthetic efficiency can be determined at an early growth stage, i.e., the 5th-7th leaf age of the early tillering stage.

6) It was clarified with the, statistical significance that there were varietal differences in net photosynthetic rate (P

7) Plant characters which have close positive relations to P

8) P

9) Net assimilation rate related positively to relative growth rate (RGR) and negatively to leaf area ratio among varieties. Namely, positive relation between NAR and RGR indicates that an increase of NAR is an important factor in increasing dry matter production.

10) Based on the analysis of the effect of varietal difference of leaf area and net photosynthetic rate to dry matter production, it was recognized that the partial contribution of net photosynthetic rate to dry matter production was nearly 30% whereas that of leaf area was nearly 70 % of the total dry matter production. Thus, under field conditions of plant population with leaf area below the critical leaf area index, any measures to increase their leaf area will be effective in increasing yields. Although the leaf area can be increased by increasing planting density and fertilizer application, the development of varieties which are characterized by large leaf area per unit dry weight, i.e., the varieties with small SLW that are able to increase their LAI at a low level of nitrogen supply is regarded as an useful approach for most of the present rice culture in Southeast Asian countries. On the other hand, the varietal improvement to increase photosynthetic efficiency may possibly be an important way to raise further grain yields with plant populations having leaf area index higher than the critical LAI.

11) From the above experimental results, 8 varieties of

刊行年月日 | |
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作成者 | Yoshikazu Ohno |

公開者 | Tropical Agriculture Research Center |

巻 | 9 |

開始ページ | 1 |

終了ページ | 72 |

言語 | eng |