Lengthening versus shortening dark periods and blossoming in sugar cane as affected by temperature.

Sugar cane, an intermediate day plant, clearly received a stronger stimulus to flower during lengthening nights than during shortening nights. Flowering was vigorous under warm, lengthening nights (21 degrees ) but less so under cool, lengthening nights (16-17 degrees ). Warm or cool shortening nights either failed to induce flowering altogether or reduced it substantially. Under the warmer nights the inductive dark period was 10 hours 57 minutes to 11 hours 26 minutes whether the nights were lengthening or shortening. Under cooler conditions, it was longer by from 20 minutes to nearly 2 hours.