Effects of Temperature, Light, and Variety in Controlled Environments on Floret Number and Fertility in Barley1

Abstract

In a series of experiments using combinations of 17 barley (Hordeum vulgare L.) varieties we studied the effects of 12, 18, and 24 C constant and 18/12 C day/night temperatures; 12‐, 16‐, and 24‐hour photoperiods; 5,500 and 22,000 luxes light intensities; and light low and high in far‐red energy on numbers of florets and perceut fertility per main head and tiller head and per plant.Number of florets per head and per plant were lowest at 24 C. Lengthening the photoperiod decreased the number of florets per head. At the low light intensity there were slightly fewer florets per head with a pronounced reduction in tillering. An increase in number of florets per tiller head was noted with the virtual absence of far‐red energy but there was no effect on tillering.Percent fertility was highest at 18 C. Tiller head fertility was further increased under an alternating day/night temperature. Plants in the 12‐hour photoperiod had the lowest fertility. Reduction in light intensity or in far‐red energy decreased plant fertility. The varieties ‘Betzes,’ ‘Palliser,’ ‘O. A. C. 21,’ and ‘Trebi’ failed to head in short photoperiods, in low light intensity, or in light low in far‐red energy.