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Bulb Development in Onion (Allium cepa L.) IV. Influence on Yield of Radiation Interception, its Efficiency of Conversion, the Duration of Growth and Dry-matter Partitioning

J. L. BREWSTER, F. M. MONDAL and G. E. L. MORRIS
Annals of Botany
Vol. 58, No. 2 (August 1986), pp. 221-233
Published by: Oxford University Press
Stable URL: http://www.jstor.org/stable/42757660
Page Count: 13
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Bulb Development in Onion (Allium cepa L.) IV. Influence on Yield of Radiation Interception, its Efficiency of Conversion, the Duration of Growth and Dry-matter Partitioning
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Abstract

Increases in total dry-matter yield during bulb growth in well-irrigated onion crops were correlated with the total solar radiation intercepted by the leaf canopy. The mean efficiency of conversion of intercepted radiation to dry-matter was 1·58 g MJ⁻¹. However, efficiencies were significantly different between seasons and in two years out of three they were lower for spring-sown crops than for autumn-sown crops. The lower efficiencies coincided with periods of high mean temperature and irradiance. The percentage of the total irradiance intercepted by the canopy during bulbing (I%) was increased by higher plant densities, earlier sowing and in later-maturing cultivars. It was higher in spring-sown than in autumn-sown crops especially at low plant densities. The duration of bulb growth was negatively correlated with I% and with the mean air temperature during bulb growth. Consequently autumn-sown crops had a longer duration of bulb growth than spring-sown crops and produced exceptionally high bulb yields at high plant densities. Non-irrigated crops had a lower I% and a shorter duration of bulb growth than irrigated crops, and a lower conversion efficiency in a season of high mean temperature and irradiance.

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