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Old 03-14-2004, 07:23 AM   #16
2la
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Quote:
Originally Posted by Basilisk
I have conducted a very rudimentary experiment about blues and reds: four sword plants (all same species, and same 'crop'), two in stronger red and two in stronger blue emissions. The result was in fact that growth pattern, compact bushy in reds and tall and thin in blues.
So you observed the opposite effect of photomorphogenesis?

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Originally Posted by Basilisk
I figure the growth pattern due to reds and blues may be caused by the red wavelenghts' quicker attenuation as depth increases. Thus, lacking enough red emissions, the plant tries to reach a "redder" spot by increasing its height rather than its span.
Unless your tank is two feet deep or deeper, the attenuation of red light with depth isn't all that pronounced--even less so given that most people keep their (background) plants not much more than six inches or so away from the lighting fixtures. (Bear in mind, also, that sword plants aren't stem plants with internodes, making the effect of photomorphogenesis--or antiphotomorphogenesis, as the case may be--difficult to validate...)
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Old 03-14-2004, 01:22 PM   #17
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I've just started my reading on the topic...got a bunch of web pages and research articles saved...but my initial scan suggests both blue and red light are involved in photomorphogenesis. The blue light affects the cryptochromes and seems to be involved in phototaxis (bending toward light) and stomatal opening (I'm not sure how that relates to submerged aquatic plants). The red light affects the phytochromes and seems to be involved with stem elongation and budding.

An interesting hypothesis from one research paper suggests that the two growth modes help plants compete for light. Consider a plant in the shadow of another. The red light is pretty much gone, but some blue light scatters into the shadow. The plant starts to bend sideways toward the source of blue light and puts more growth into stem elongation (too little red light). As it grows toward the edge of the shadowed region, the source of blue light moves toward the top of the plant canopy. The plant starts to grow vertically and continues to elongate to grow above the competing plants as quickly as possible.

So my evolving hypothesis for the action modes of the GE 9325K is that the increased blue intensity kicks up the photosynthetic rate pretty well by hitting the blue sweet spot on the action spectrum. The increased red intensity might provide some increase in photosynthetic rate as well, but misses the red sweet spot on the action spectrum. However, the red light regulates the vertical growth and might cause the plants to be bushier than they would be with less red light.

Everything I've read so far seems to ignore the green light or dismiss it outright. Seems like the green light emissions are more for our visual benefit than the plants. The green light hits the sweet spot in the photopic curve for the human eye, but both the blue and the red are in regions of low eye sensitivity. Without the green light, the bulbs would look extremely dim, even though they might be producing adequate light energy for the plants.
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Old 03-14-2004, 09:56 PM   #18
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I feel dumb for I had thought for long the effect was opposite. I guess taking my results for correct, I didn't really pay attention to books and texts stating it just opposite, a perception/attention 'flaw' of the mind, but that is psychology, and still, my shameful mistake.

I stated also a misfitting description for the plants in red light. They wasn't actually compact, but thicker or denser. The rosette had a shorter span, but because of the shorter peduncles, shorter than in the ones in blue light. Can't explain that, but it was so. It seemed a coherent conclusion to me. We used regular coloured incandescent bulbs, and had no idea of the spectra, and the sampling species was (I know now, thanks 2la) not suitable for the experiment--I was in junior high, and about 13.

2la wrote:
Quote:
Unless your tank is two feet deep or deeper, the attenuation of red light with depth isn't all that pronounced--even less so given that most people keep their (background) plants not much more than six inches or so away from the lighting fixtures. (Bear in mind, also, that sword plants aren't stem plants with internodes, making the effect of photomorphogenesis--or antiphotomorphogenesis, as the case may be--difficult to validate...)
I didn't mean the attenuation was in our tanks, but in the wild. I suppose a plant that would be three feet or deeper underwater, would try to reach up for red light. However, due to the low depth of our tanks, if a lighting fixture lacks enough emissions of the red portion, it will be almost all the same in point of depth. I think the plant could "feel" like it is too deep for it, and then try to reach up, but never finding the spot. Although that would mean that eventually it would come out of water, which I can't explain, rebate or confirm.

I agree completely with bad choice of plants for the experiment.

It would take me a lot of proper experimentation to prove if some principles/phenomenons work differently for water plants.

Thanks for corrections to my lousy suppositions.
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Old 03-15-2004, 01:51 AM   #19
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Easy on yourself, Basilisk. There's nothing shameful about mixing up the principles of photomorphogenesis--most people couldn't even say it! :lol:
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Old 03-15-2004, 01:54 PM   #20
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Definitely don't go hard on yourself, Basilisk. I was going to say the same thing - The attenuation of red light in a typcial aquarium isn't drastic, but it is certainly significant. Most wavelength-specific attenuation coefficients I've encountered in text have shown that there is significant (20-30%) attunation of red wavelengths within the first 2 feet. That might not be enough to break the proverbial bank as far as growth goes, but it might be enough to coerce increased internodal spacing, since the plant is recieving somewhat more energy at the top end of the plant than at the very bottom.
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Old 03-16-2004, 05:28 AM   #21
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Thanks, it's ok. I did take that concept as good a long time, and I was proud of my discovery. I should have been more humble.
Anyway, I'll have plenty of study time next semester when I switch to biology school. I hope that will turn into worthy contributions.
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