Suppression of long-day flowering by nitrogenous compounds inLemna perpusilla6746

摘要

The long-day flowering ofLemna perpusilla6746 on an SH inhibitor-containing medium was inhibited by the application of ammonium ion to the medium. Ammonium ion not only suppressed long-day flowering, but relieved the inhibition of vegetative growth caused by the inhibitors. Nitrite, casamino acids, glutamine and asparagine had a similar effect, suggesting that the inhibition of long-day flowering by ammonium ion is not a direct effect of the ion. Most amino acids, with the exception of glutamate and aspartate, also prevented long-day flowering, but their effects on vegetative growth varied. No qualitative differences in amino acid composition were observed among plants cultured on media containing nitrate, nitrite or NH44NO3as the sole nitrogen source. However, the amounts of free and total amino acids werehigher in plants fed with nitrite or NH4NO3than in those fed with nitrate. This suggests that the inhibition of long-day flowering by ammonium and nitrite can be ascribed to increased nitrogen metabolism.Though decreased activity by SH inhibitors of nitrate reductase (SH enzyme) is assumed to result in long-day flowering by lowering the nitrogen metabolism, lowering the nitrogen level in M medium did not bring about floral initiation in the absence of SH inhibitors.