Short photoperiods induce fructan accumulation and tuberous root development in Dahlia seedlings

. The effect is reported here of photoperiod on fructan accumulation in the tuberous roots of Dahlia sp. cv. Sunny Rose seedlings. . Growth parameters were measured of shoots and roots on glasshouse-grown d ahlia seedlings subjected to either short day (SD) or long day (LD; 4 h nig ht photoperiod interruption) light regimes. The carbohydrate concentrations of tuberous roots was analysed by high performance anion exchange chromato graphy. . Total plant dry weight was unaffected by photoperiod. The LD treatment in hibited tuberous root development but increased shoot dry weight. Tuberous root tissue of SD seedlings showed a 156% increase in total fructan (inulin ) concentration compared with LD tuberous root tissue, which had higher red ucing sugar concentrations than SD tuberous roots. A wide range of oligomer s increased during the SD treatment. . Sucrose appears to be the regulating factor in fructan metabolism in dahl ia. Photoperiod is a valuable tool for studying fuctan metabolism in vivo, as it provides a nondestructive means of regulating sucrose partitioning.