Effects of Growing Temperatures and Day Length on Flower Bud Initiation and Development in Sweet Pepper

Abstract

The effects of growing temperatures and day length on flower bud initiation and development were investigated. Three sweet pepper cultivars, ‘California Wonder, ’‘Shin-sakigake’and‘Shishito’were transferred to the phytotron and exposed to temperatures of 15°C, 20°C, 25°C and 30°C at the unfolding time of the cotyledons (Exp. 1) or at the time of flower bud initiation (Exp. 2) . The plants were grown at these temperatures under natural, (short) day and also under long day.
As the growing temperature rose, the number of nodes on the 1st flower bud decreased (except 15°C) . The flower bud was initiated at only 15°C and under long day. Comparing the number of nodes in the three cultivars at the budding, the lowest was 10.9 of ‘Shin-sakigake’ and the others were 11.3 and 14.5 for ‘California Wonder’ and‘Shishito, ’respectively. The higher the growing temperature, the fewer the number of days for the initiation of the 1st flower bud.
The number of days for the initiation of the 1st flower bud decreased more under long day than short day in the three cultivars. The difference of these days under long day and short day was smaller as the growing temperature rose and the flower buds were formed almost at the same time under both day lengths at 30°C. The effect of day length on the number of nodes on the 1st flower bud was not clear. Though the budding of the three cultivars was promoted as the temperature rose, the budding at 25°C and 30°C occurred alsmost simultaneously.
From these results, it is deduced that the 1st flower bud of the three cultivars used is formed earlier and at a lower node as the growing temperature rises. It seems that the 1st flower bud is formed earlier under long day than that of short day but the effects of day length on the number of nodes to the 1st flower bud was not clear.