THE INFLUENCE OF VARIETY, TEMPERATURE, AND STAGE OF GROWTH ON THE RESPONSE OF SPRING BARLEY TO PHOTOPERIOD

Abstract

Olli and Vantage barley were grown in plant growth chambers under 27 combinations of photoperiod at continuous temperatures of 55° and 75°F. in two consecutive experiments. The photoperiod treatments (8, 16 and 24 hours) were applied during seeding to internode elongation (Stage I), internode elongation to heading (Stage II), and heading to maturity (Stage III) of the first culm.Increases in photoperiod during Stage I reduced the number of days from seeding to internode elongation and heading but increased the number of days from heading to maturity, reduced leaf number and height, weight of stem and head, stem length, head length, number of florets and kernels per head, and fertility for the first culm. Time of initiation of tillering relative to elongation of the first internode of the first culm was advanced for Olli but delayed for Vantage with the increases in photoperiod. Tillering extended over a longer period and tillers were more numerous under 16- than under 8-or 24-hour photoperiods during Stage I.Increases in photoperiod during Stage II reduced the number of days from internode elongation to heading but generally increased leaf, stem and head development, and fertility for the first culm, and increased the number of fertile tillers. Increases in photoperiod during Stage III reduced the number of days from heading to maturity of the first culm and increased the number of fertile tillers.An increase in the temperature from 55° to 75°F. reduced the duration and extent of development of the first culm, delayed commencement and reduced duration of tiller initiation, and reduced the number and extent of development of the tillers. The influence of temperature decreased with increase in length of photoperiod.Olli and Vantage differed in duration of leaf initiation and number of leaves associated with the first culm, in kernel weight and in the relative time of initiation of tillering. They were essentially similar in duration and extent of stem and head development and fertility for the first culm, in the duration of tillering and number of tillers produced, and in the extent of stem, head and kernel development of the tillers.There were significant associations of number of days from seeding to internode elongation with number of leaves on the first culm, among stem length, head length, number of florets per head and weight of the stem and head, and of number of tillers with duration of tillering.