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Abstract
A comparison of the effects on vegetative growth of 8 hr. and of 16 hr. of light per day at various temperatures was carried out with 9 species of pasture plants grown in New Zealand. The temperatures used were 45°F, 55°F, 65°F, 75°F, 85°F, and 95°F. The light intensity was constant at approximately 2,700 foot candles. Hence in these experiments an increase in photoperiod from 8 to 16 hr. of light was accompanied by a doubling in quantity of light per day.
The influence of the various levels of temperature on the rates of growth and tillering of individual species was similar to that found earlier for plants grown with a 12 hr. photoperiod. However, optimum temperatures tended to be lower with 8 hr. than with 16 hr. of light, particularly for rates of tillering.
At the lower temperatures the increase in photoperiod from 8 to 16 hr. generally gave only a small increase for rate of tillering and in some cases possibly decreased it; but it generally more than doubled daily growth on an individual tiller. Such effects were most apparent at 45°F, generally decreased at intermediate temperatures (55–75°F), and in some cases were reversed at 95°F.
