Plant and Cell Physiology, 1986, Vol. 27, No. 6 1153-1158
© 1986
Article |
Inhibition of Flowering in the Long-Day Plant Lemna gibba G3 by Hutner's Medium and its Reversal by Medium Modification
1Smithsonian Environmental Research Center 12441 Parklawn Drive, Rockville, Maryland 20852-1773, U.S.A.
2Department of Biology, Faculty of Science Konan University, Kobe 658, Japan
The long-day plant Lemna gibba G3 flowers normally in E medium (Hoagland-type medium plus 30 µM EDTA) but in 0.5 H medium there is no flowering. Ammonium is present in 0.5 H medium and is known to inhibit flowering in L. gibba G3, but even in NH4+-free 0.5 H medium there is virtually no flowering under continuous light. Increasing the phosphate concentration of the NH4+-free 0.5 H medium from 1.15 ITIM to 12 or 16 mM results in substantial flowering. Decreasing the EDTA concentration from 850 µIM to 250 µM, or raising the nitrate concentration from 4 mM to 12 mM, results in only a small increase in flowering. If the decrease in EDTA and increase in nitrate are combined with the increase in phosphate, however, the flowering response is nearly as good as that obtained using E medium. Thus, with these three changes the inhibitory effect of NH4+free 0.5 H medium for flowering in L. gibba G3 is almost completely reversed
In the above studies flowering was not limited by daylength. When plants were grown on E medium under an 11 hour daylength where flowering is limited by daylength, decreasing the phosphate concentration in the medium reduced flowering, but increasing the phosphate concentration in the medium did not stimulate flowering. Thus, when flowering is limited by daylength, high phosphate will not cause flowering, but a certain level of phosphate appears to be necessary for the expression of photoinduction under long days.
(Received January 14, 1986; Accepted June 24, 1986)
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