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Growth and Dormancy in Lunularia cruciata (L.) Dum.: VI. GROWTH REGULATION BY DAYLENGTH, BY RED, FAR-RED, AND BLUE LIGHT, AND BY APPLIED GROWTH REGULATORS AND CHELATING AGENTS

W. W. SCHWABE and I. F. M. VALIO
Journal of Experimental Botany
Vol. 21, No. 66 (February 1970), pp. 122-137
Published by: Oxford University Press
Stable URL: http://www.jstor.org/stable/23688437
Page Count: 16
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Growth and Dormancy in Lunularia cruciata (L.) Dum.: VI. GROWTH REGULATION BY DAYLENGTH, BY RED, FAR-RED, AND BLUE LIGHT, AND BY APPLIED GROWTH REGULATORS AND CHELATING AGENTS
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Abstract

Experiments with photoperiods ranging from 2 to 24 h confirm that 8 h light per day is optimal for Lunularia: there is no growth in the dark or in continuous light, which causes the rapid onset of dormancy. Short-day cycles intercalated among a series of continuous light cycles promote growth; in cycles longer than 24 h very long dark periods are detrimental. With very short photoperiods (5 min) red light promotes growth more effectively than white light at higher intensity; far-red acts as dark. The growth effects of red and far-red light breaks (3 min) depended on the time of application; red light inhibited in the middle but promoted at the beginning of the 16-h dark period of a short day; far-red light had the opposite effect; in each case red and far-red effects were reversible by the other wavelength. Blue light gave the same response as red including the reversibility of far-red effects and vice versa. Surprisingly, significant effects of 5 min red, blue, and far-red irradiation were also found in the middle of the main high-intensity white-light period, red and blue promoting growth, far-red reducing it; again there was ready reversibility of the effects. Growth promoters of higher plants are generally inhibitory to Lunularia or have little effect; among growth retardants TIBA, Phosphon D, and CCC gave a slight promotion of growth. EDTA promoted growth (cell numbers) very significantly while 8-hydroxyquinoline was initially inhibitory, but had a marked latent promoting effect when subsequently washed from the thalli.

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