Below are a small part of an articel focusing on light on terrestial plants. There's much I don't get in this, since english is not my first language, but from what I understand i says that at a certain kelvin rate, the light seems like the light that can be found underneat a canopy of leaves, and this light will make the plant struggle to grow upwards towards the canopy to get to the light itself. On the other hand, and a nother specter of light, it works like direct sunlight, so the plant focus on good sidegrowth.
here's the articel in full: http://220.127.116.11/akvarienet/me...antsfile54.pdf
And the part we are looking for:
5.3 Stem elongation
As described in section 2.2, far-red light reflected by neighbouring plants (or neighbours for short) decreases R:FR in horizontally propagated light, as ‘seen’ by vertically oriented plant surfaces (see Aphalo and Ballaré, 1995). This happens at low canopy densities, so it is especially important for small seedlings in sparse canopies.
The stems of many plants elongate faster if they receive additional far-red light from the side (see Ballaré, 1999, and references therein). In general, the magnitude of the response to far-red
light depends on the species, developmental stage, and other environmental variables such as blue light and/or photosynthetically active irradiance incident on the leaves. However, at low canopy densities there is no actual shading of leaves by neighbours. When measured under laboratory conditions, the stem elongation response to far-red light incident on the stem can be shown to have a very short lag (of the order of minutes in small seedlings) but continue for some time after the end of the stimulus (Casal and Smith, 1988a,b).
The photoperception of the lateral far-red light takes place in the growing internodes. In sparse canopies, the perception of neighbours is mediated mainly by phyB and probably sensitivity is modulated by phyA6.
Intensiteten och den blåa delen av spektrat verkar inte ha någon betydelse om man kollar på den bild han visar (Figure 11) där han jämför HighLight (HL) och (LowLight) och antingen Far-red eller Red.
This has been dicused on a swedish forum the last few days, and many of the skilled plantedud's there seems to swear to 10,000 kelvin bulbs for good growth and strong red collors. I have always been under the expercion that around 5500kelvin was the only way to go. Anybody here had any experience with bulbs in this range for a freshwater planted tank?
Also, I'm wondering if I should try this over my tank. What would be the best combination, two 10,000 kelvin 150W MH, or 4 70W, two at 5000 kelvin and two at 10,000 kelvin?