My completely unprofessional thoughts are that you are not suffering from a lack of light at all. The far red light (730nm and above) is sending a signal to the plant that there are other plants above it. As a result it is growing taller to compete.
Why?
Longer wavelengths generally penetrate much deeper into leaf tissue and appear to be the main range of wavelengths that reach below the canopy. The plant seems to respond to this imbalance by reaching higher to compensate. I guess you could classify it as a "shade avoidance" tendency. I've had a similar problem with red-heavy lights and got the situation back under control by simply turning off the far reds.
The tendency for shade avoidance combined with the Emerson effect leads to a healthy though slightly yellow plant that is very tall and lanky (but still fundamentally viable.)
If you think about this tendency in the context of plants that stretch in dim light, it's really the same thing. The Color Signals that it's receiving tell the plant that there must be competitors stealing it's light.
The other side is that in flowering, far red can tell the plant that fall is coming (the sun is lower in the sky) and as a result, those competitive instincts can lead to more bud sites, as the plant become more sexually frustrated, and knows it needs to mate.
Listen to Dr. Bruce Bugbee talk about this at minute 12:00 in relation to cell expansion.
Why?
Longer wavelengths generally penetrate much deeper into leaf tissue and appear to be the main range of wavelengths that reach below the canopy. The plant seems to respond to this imbalance by reaching higher to compensate. I guess you could classify it as a "shade avoidance" tendency. I've had a similar problem with red-heavy lights and got the situation back under control by simply turning off the far reds.
The tendency for shade avoidance combined with the Emerson effect leads to a healthy though slightly yellow plant that is very tall and lanky (but still fundamentally viable.)
If you think about this tendency in the context of plants that stretch in dim light, it's really the same thing. The Color Signals that it's receiving tell the plant that there must be competitors stealing it's light.
The other side is that in flowering, far red can tell the plant that fall is coming (the sun is lower in the sky) and as a result, those competitive instincts can lead to more bud sites, as the plant become more sexually frustrated, and knows it needs to mate.
Listen to Dr. Bruce Bugbee talk about this at minute 12:00 in relation to cell expansion.
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