DOES DIURNAL TEMPERATURE FLUCTUATIONS (DIF) REGULATE INTERNODE LENGTHS MEDIATED THROUGH THE BIOSYNTHETIC FORMATION OF GA1 IN BEGONIA X HIEMALIS FOTCH?

J. Myster, R. Moe, O. Junttila
It is shown that the difference between day and night temperature (DIF) has a great effect on internode elongation in many plant species, including Begonia x hiemalis. Can this effect of DIF be explained from specific influences of plant hormones? Research work is been done in B. x hiemalis to find out if the regulation of internode elongation by DIF is mediated through changes in the GA metabolism. Plants of B. x hiemalis cv. Aphrodite Pink were grown in a daylight phytotron at 24/14 °C, 19/19 °C and 14/24 °C here defined as positive-, zero-, and negative DIF, respectively. The plants were treated with ent-kaurene, kaurenoic acid, GA12, GA19, GA20, GA1 (2x10 μg per plant), BX-112 and a combination of GA1 and BX-112. The suggestions about the growth regulator BX-112 is that the compound inhibits the turnover for GAs in the so-called 13-hydroxylated pathway.

Mean internode elongation shows a typical DIF response, where the difference of the means between positive DIF and zero DIF is greater than the difference between zero DIF and negative DIF. Plants treated with the combination of GA1 and BX-112 and the GA1 treated had the greatest internode elongation compared to the control at the same temperature. There seems to be no effect of the other treatments with ent-kaurene, kaurenoic acid, GA12, GA19, GA20 and BX-112. The internode elongation on plants treated with the combination of GA1 and BX-112 seems to be a bit greater than GA1 treated plants, and this supports the hypothesis that BX-112 inhibits the turnover from GA1 to GA8. The possibility that there might be another important pathway for the biosynthetic formation of GA1 in B. x hiemalis are discussed.

Myster, J., Moe, R. and Junttila, O. (1995). DOES DIURNAL TEMPERATURE FLUCTUATIONS (DIF) REGULATE INTERNODE LENGTHS MEDIATED THROUGH THE BIOSYNTHETIC FORMATION OF GA1 IN BEGONIA X HIEMALIS FOTCH?. Acta Hortic. 378, 123-128
DOI: 10.17660/ActaHortic.1995.378.16
https://doi.org/10.17660/ActaHortic.1995.378.16

Acta Horticulturae