THE EFFECT OF ELEVATED ROOT ZONE TEMPERATURES OF VARIOUS DURATION ON GROWTH AND DEVELOPMENT OF SEVERAL POINSETTIA CULTIVARS

Poinsettia plants (Euphorbia pulcherrina Willd, cv.) respond differently to root zone heating (RZH), depending upon cultivar, media temperature and duration of heating.
The number of axillary shoots developing was not increased when pinched plants received elevated root zone temperatures from 4:00 p.m. to 8:00 a.m. throughout the growing season.
Branching, however, was stimulated in unpinched plants depending upon variety when elevated root zone temperatures were applied continuously (24 hr/day) throughout the growing season.
Axillary shoot length was stimulated in both pinched and unpinched plants.
Continuous root zone heating of unpinched plants resulted in plants with shorter main stems but relatively longer axillary shoots.
Pinched plants receiving elevated root zone temperatures from 4:00 p.m. to 8:00 a.m. daily had longer axillary shoots, and the plants produced tended to be taller than controls receiving no root zone heating.
Root zone heated plants receiving a Cycocel drench (3 000 mg/l) were not significantly taller than control plants receiving the same Cycocel drench.

Root zone heating consistently led to earlier plant maturity as characterized by bract size, total anthocyanin, and cyathia pollen development, the consequences being a somewhat shortened production period.

III International Symposium on Energy in Protected Cultivation

G.J. Wulster, H.W. Janes

https://doi.org/10.17660/ActaHortic.1984.148.109