Effect of Photoperiod on Growth and Development of Cassava (Manihot esculenta Crantz)

Abstract

Effects of photoperiod on growth and development of cassava were studied in controlled environments. Plants of cultivars M Aus 7 and M Aus 10 were grown under short (10-h) and long (16-h) photoperiods and harvested at approximately weekly intervals for a period of 13 weeks. Long photoperiods resulted in large increases in leaf area through increases in both number (both cultivars) and size of leaves (M Aus 7 only). The timing, extent and anatomical characteristics of storage root initiation were similar for both cultivars under 10-h and 16-h photoperiods but the subsequent balance between shoot and storage root growth strongly favoured shoot growth in long days. Dry matter partitioning followed a simple allometric pattern with the proportionality between the relative growth rate of shoots and the relative growth rate of storage roots remaining constant with time but being altered by photoperiod. Distribution to storage roots was quantitatively reduced in another experiment using M Aus 10 with each additional 1-h increment from 10-h to 16-h photoperiods. A treatment consisting of a short day (10 h) plus a 1-h night break in the middle of the dark period produced growth similar to long day treatment. Differences in cultivar response (Ceiba, CMC 84 and M Aus 7) to a range of photoperiods (11, 12, 13 and 14 h) were detected in a third experiment. The possible mechanisms and significance of these responses are discussed.