Mike and Star- please don't hesitate to discuss anything you care to.
I'll even join in!
Pine would probably be my last choice unless I had no options. Even paying for
number one pine isn't going to buy stability and strength.
I remember when I was young some nice blocks and 2"x 12" pine worked very well. :)
Most pine that I've used is fast grown and weak.
Nothing would be worse than to do all that work and a week later
all the shelves bowed and twisted into a big mess.
For strength I'd use plywood. I'd also spring for furniture grade and
should I decide not to paint -not a problem.
I've been using Red Oak for all my shelves in the shop. I can understand
why you may not want to run the cost up but if you want that built in
to fall into "furniture" then personally I'd rather have a smaller quality unit
than a big oh-hum unit. Not an easy call.
May seem wrong but you do know that a piece of tubing supports more than a solid rod- something to consider. ( horizontally thinking :)