Once the environmental trigger starts the process, it's going to continue to completion. In a lab environment it may or may not be possible to revert a given plant to it's previous stage by manipulating light/dark periods, but in 'the real world' once the night length triggers the response it's not going to change before the growth stage is complete.

It is my understanding that there is a certain plant that some choose to grow indoors with artificial lighting where they do intentionally manipulate the dark period to induce flowering. These persons are typically pretty careful to ensure that the dark period is not interrupted prematurely lest the plant cease it's flowering. This would be roughly akin to a lab environment and something not commonly found out of doors.

thanks JAG. After that answer i better give more information about what i'm trying to grow ; )

i have these bean plants (10 Aztec Half Runners) that i planted around the beginning of November. About half started to flower and then just stopped which seems strange. The other plants haven't flowered at all so far. i know some bean plants are DL sensitive and i know that my Christmas Cactus flowers once at Thanksgiving and then again around Easter time so i started wondering if there was a connection.

There may be a connection. But generally speaking, day length sensitivity in beans boils down to them not flowering until the days are shorter. Therefore, I'd suspect that, rather than a day LENGTH issue, you may be dealing with a something more like not being able to get enough light.

George
Tahlequah, OK

Thanks George.

i think you are right that they are not getting something they need, they sprang up to about a foot high pretty quickly and then just stopped. We are getting about 11 hours of daylight now but it has been mostly cloudy (and wet) the past few weeks. Looks like fair sunny weather this week so it's wait and see.