Flowering Responses of the Long-day Plant Lemna gibba G3

Abstract

Suntmary. Lenmna gibba L., strain G3, exhibits a qualitative long-day flowering response with a critical, daylength on a 24-hour cycle of about 10 hours. Evidence is presented that the onset of daughter frond formation in a given frond inhibits the activity of the flowering meristem. Consequently, flower induction can only occur in fronds smaller than about 0.05 to 0.07 mm lon;g. Although a minimum of 1 long day seems to be sufficient to induce the formation of flower primordia, at least 6 long days are required to obtain mature flowers since long days are also required for the early stages of flower development. The critical night length on 24, 48 and 72-hour cycles is respectiveilv 14, 16, and 18 to 22 hours. The close similarity between the critical night length for the different cycle lengths is explained in terms of an inhilbitory effect of darkness both on flower initiation and, flower development. A 10-hour dark period is more inhibitory to flowering on a 36-hour cycle than on 24, 48, 60 or 72-hour cycles. It is suggested that darkness inhilbits flowering through the formation of a light-labile flower inhibitor which acts to inhibit the funlctioninig of the flowering stimulus.Studies on the physiology of flowering have been carried out with a large number of dlifferent plants, but generally speaking the processes which control flowering are much better understood in short-day plants than in long-day plants. One reason for this situation is that most long-day plants gro-w rather slowvly, require several to many long days for flower induction and do not exhibit maximum photoperiodic sensitivity until they reach an age of 1 to several months or nmore. Thus detailed information concerning the various factors which interact in the control of flowering has been obtained for only a few longday plants such as Loliumt temulleitutim, Hyoscyarnus niger and Silente arnmeria (16). In view of the somewhat limited informnation available on the physiology of flowering of long-day plants, a detaiilied study was undertaken into the flowering response of the long-day plant Lemnna gibba strain G3.The first demonstration of unequivocal control of flowering in the Lemnaceae was by Kandeler (12,13) who showed that several strains of Lemnia gibba, including strain G3, exhibited a long-day flowering response. Kandeler (12) indicated that the critical daylength for L. gibba G3 was between 10 anid 12 hours, but did not give any suipporting evidence.

Identification of the Flower-inducing Factor Isolated from Aphid Honeydew as being Salicylic Acid

“…Application of salicylic acid to vegetative Xanthium either alone or in combination with gibberellic acid and/or kinetin has no effect on flowering (Cleland, unpublished (4). In addition to stimulating flower initiation, long days also stimulate flower development in L. gibba G3 (6), but preliminary experiments suggest that salicylic acid has only a small effect on flower development. It is clear that salicylic acid is able to mimic the effect of long days on flowering and growth to a remarkable degree.…”

“…The long-day plant Lemna gibba L., strain G3, was used as the bioassay plant. The growth medium and culture conditions were the same as previously described (5,6). Salicylic acid was added by sterile filtration to previously autoclaved medium.…”

“…Control flasks received 1.5 ml of distilled water. Flowering was evaluated as previously described (5,6).…”

Effect of Low-intensity Red and Far-red Light and High-intensity White Light on the Flowering Response of the Long-day Plant Lemna gibba G3

“…Lemlna gibbci, strain G3 has l)een shown to exhibit a qualitative long-day flovvering response w-ith a critical daylength on a 24-hour cycle of about 10 hours (5). The influielnce of low-intensity red and far-red light on L. gibba1 has been examined( only very briefly.…”

Selection and Characterization of [alpha]-Methyltryptophan-Resistant Lines of Lemna gibba Showing a Rapid Rate of Indole-3-Acetic Acid Turnover

“…tions. A single mother/daughter two-frond pair was grown under standard conditions; 50 mL of E medium (Cleland and Briggs, 1967) in a 125-mL flask kept in a growth chamber (model Q6521, Environmental Growth Chambers', Chagrin Falls, OH) at 26°C undei. continuous light, provided by a mixture of cool-white fluorescent and incandescent lamps at 25 pmol m-'s-' (Slovirt and .…”