I have heard that a green light will not effect the flowering cycle, and will let you work on your plants when the main lights are off. Is this true?
I still setting up my grow and I won't always be able to get to my plants on time, so if this is true it would be a good option for me.
I know it's an old thread, but seems to have stayed alive over the years, so just wanna throw my 2c in it.
So the general advice of not interrupting the flower-cycle, of short-day photoperiodic plants (ie. Cannabis), is to have them into UNINTERRUPTED DARKNESS during lights out. There has been some recent research by Prof. Bugbee et al that showed that even IR wavelengths (those which are used for IR monitoring in night-vision cameras) can delay flowering:
Photons from NIR LEDs can delay flowering in short-day soybean and Cannabis: Implications for phytochrome activity
So it stands to reason that wavelengths inside PAR can also do this, or even way better. Now aside from photosynthesis plants possess photoreceptors which they use to sense the spectrum, weigh its relative strengths and answer to it via photomorphogenics or phototropism. The responsible receptors absorb mostly, and heavily, in the UV/blue and red/darkred region. There is a small gap within the green wavelengths, however just because there is very little or next to none absorbtion doesn't mean the plant won't react to it; and this has several reasons:
- Plant receptor chromophores are highly sensitive and only need about 1umol/m^2/s fluxstrength to react accordingly.
- Greenlight can cause a yellow, red or darkred fluorescence that then is absorbed by photoreceptors within the leaf, and since both of this happens right inside a leaf it may escape any notice from outside measuring equipment.
- Greenlight can still drive photosynthesis and this is accompanyied by several sideeffect such as stomatal opening, phototranspiration etc - which is something a plant may not be used to during a real nightphase.
- Research by Prof. Folta et al showed evidence of a specific greenlight-reaction of plants that could be interpreted by having a still unknown greenlight receptor at large (e.g. see:
Green Light Stimulates Early Stem Elongation, Antagonizing Light-Mediated Growth Inhibition)