Solar Glass - Pilkington K and plant growing

That's excellent Kristen. Most interesting. Like you I have read about the effect of light on plant growth, but forgotten most of it.

As always, things are even more complicated. There is also an effect of the ratio of red to blue light. This ratio sends signals to the plant to do various things. The most obvious is to etiolate (ie grow leggy) when the ratio of red and infrared (ie heat) rises too high. This is another way of saying that the plant will get leggy if it gets too much heat and too little light. The plant detects this as the ratio of the different wavelengths. But this ratio can also tell it to do other things as well.

 

Poinsettias won't do the red-bracts Christmassy thing without long nights (IIRC there must be absolutely no light in that time, so a quick flick of the light switch on the room they are in can wreck things, but I may be over dramatising that!) Anyway, I routinely fail to keep the things alive from one Xmas to the enxt ... let alone get the opportunity to try the red-bracts darkness thing.

 

John - I meant to say earlier that I love the discovery of things like the fact that plants don't absorb green light. There are so many things that we know or learn about and often much later when we discover the reason - we say oh! is so obvious.

At school I was told that the earth's core consisted of molten iron. But nobody ever explained why. Years later I discovered the reason. Iron is the most atomically (not chemically) stable element. In the sun it is the fusion of hydrogen atoms into helium that release energy. Then the helium atoms fuse to produce carbon, and so on till they reach iron, then they stop. At the other end heavy elements such as uranium will break up into smaller pieces and release energy, and that in theory will go on until they reach iron and then stop. - so the whole universe will eventually end up as heavy metal. :D

Yes Kristen, I have read that long days are not the same as short nights. The trouble I have is in remembering all the individual facts about how different plants react. It would be so much nicer if there was a consistant underlying principle and they all followed that. But it doesn't seem to be the case. Much of what goes on in the plant world is a mass of exceptions. I do understand Einstein's urge to find one unified theory of everything.

 

"I wish I could remember all that stuff from my school days"

There is no point I read that 50% of what you learn at school was discovered in the last 50 years. So even if you had remembered it all you'd still only know half what your kids know :D

 

Too true. I did physics a long time ago, and our lecturer in electronics said that he only knew about valves - so that is what he was going to teach us. Even thought it was in the era of the transistor. And I believe today even the modern transistor has been replaced by something called - the chip. :D So even if I could remember what I had learnt about valves - it might not be so useful today.

 

Yeah, bet you couldn't do MP3 decoding with Valves!

 

K glass greenhouse and tomatoes

I found this thread whist trying to see if anybody else had posted problems growing tomatoes under K glass.

Several years ago my neighbours trees forced me to abandon the old greenhouse to the grape vine and build another. I had a lot of double glazing units around so I built the new one out of these using fence rails for the frame. It worked great and took very little heating though I need to paint with cool-glass in summer and I have a massive extract fan and auto windows as a back up to stop it getting too hot. All seedlings germinate fine but I rarely get a decent crop of tomatoes. Experimenting, I've found the poly-tunnel and even the old shaded greenhouse do a much better job with the same varieties planted at the same time. Other plants don't seem to be affected.
Has anybody else here noticed anything like this?

 

Hi Caldinarod - and welcome to the forum.

Its nice to have some feedback on K glass. Its one thing to theorise, but thats not the same as experience.

I would love to know what makes optimum growing conditions. I grow a lot of plants from seed and some do wonderfully well and others do almost nothing.

 

Thanks for the replies and warm welcome! I was concerned the thread might be dead after all this time since you started it.

Unfortunately, the filter effect of K glass would not be affected by reversing it but the insulating effect would be. It works a bit like a one way mirror to infra-red allowing it in to the room but reflecting it back when it tries to escape. If I turned it round it wouldn't let as much heat in which would be good in summer but I'd need more heating in winter. The incidental filter effect to more visible light would be the same both ways.
It is a great shame things don't grow so well because most double glazing manufacturers make mistakes and then have to pay to have the wrong size units taken away so are more than happy to give them to gardeners (or at least they are in my area).
I've not noticed any trouble with germination or small seedlings though I have noticed they seem to need more ventilation to avoid damping off or overheating - could be just lack of drafts I suppose.