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Crop-scientific studies on the yield-forecast of lowland rice VIII. Effects of shading at different growing stages of rice upon the yield and yield-constitutional factors

Matsushima, Seizo; Yamaguchi, Shunji; Okabe, Takeshi; Komatsu, N.

Proceedings Crop Science Society Japan 22(3/4): 105-106

1954


Accession: 024419617

In order to make clear how and when the yield of rice and its constitutional factors are determined, experiments on shading were conducted at an interval of 10 days after transplanting, using linen cloths to cover the plants. The experiments were conducted in 1951 and 1952, in a paddy field, using 4 randomized blocks and a medium maturing variety, Norin-No. 25. The results of 2 years of experiments are in close agreement, and they are: Effects of shading on number of heads per unit area were minor. The most striking effect of shading on number of spikelets per head was found at the period from 15 to 16 days prior to heading, and at the succeeding period no effects were observed. Anatomical investigation done in the past revealed the fact that a large majority of spikelets in a given hill differentiates in the period from 15 to 16 days prior to heading. Highly significant differences in fruit bearing percentage were found among the plots. No effects of shading were found in all the plots treated during the period until 6 days prior to heading, but marked effects appeared in those treated in the period from 5 days prior to heading to 10 or 20 days prior to maturity. In the period when the development of caryopsis takes place more actively, the effect of shading comes out more strongly. Remarkable effects on weight of 1,000 grains were found in the 2 separate periods, the first was 15-16 days prior to heading and the second was 14-23 days after heading. Remarkable effects on yield were found in the two periods, 15-16 days prior to heading and 14-23 days after heading.

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