Effects of temperature on spikelet number of wheat

Abstract

The number of spikelets on the primary inflorescence of wheat was shown to vary with temperature per se in addition to any vernalization effects.

Temperature affected spikelet number principally by influencing the rate and duration of appearance of primordia after floral initiation. However, in the absence of seed vernalization in cultivars responsive to vernalization, temperature also affected the number of spikelets arising from primordia already present on the apex at initiation.

Maximum spikelet number resulted from intermediate temperatures which varied in 13.5-hr photoperiods from 10/5°C for Sunset to 22/17° for Mexico 120. There was an interaction with day length: most cultivars reached maximum spikelet number at lower temperatures in short days than in longer days. When the total amount of illumination was increased by providing a longer period of fluorescent light, spikelet number was increased with little interaction with other factors.

The rate of appearance of primordia on the primary apex increased at the time of floral initiation.