Effects of salt in preferment?

Hi,
after reading a very interesing article about the importante of salt and acidity for the structure of rye breads I verified that adding salt in the dough really seems to slow down the action of enzymes.

Since I was frustrated by the melt-down effect of my rye SD on wheat levained I made several tests: I prepared a biga with 10 gr of SD, 40 gr of water with 1 gr of salt dissolved in it, plus 100 gr of white flour. The biga raised perfectly in 12 hours, but what's most important the dough didn't have the slightest sign of deterioration: it was perfectly intact, even more firm than what I get with a white flour SD. I'm speaking of average-gluten flour, not high-gluten (that I use only when strictly necessary).

Test repeated with 2.5% of salt/flour with 75% hydratation: once again perfectly succeeded with no deterioration. I'm going to eat the pizza today ;)

I repeated the test on a poolish: 10 gr of rye SD in 100 gr of water with 1 gr of salt and 100 gr of flour. In 12 hours the poolish grew very little, maybe 20-30 percent, not more.

I wonder why there was such a dramatic difference in behaviour.

I thought that salt had a bad effect on yeasts in general and I always cared to add it at the very last moment as last element, but apparently rye SD doesn't seem to suffer from it. I still have to see what effect salt has on bigas made with my white flour SD.

Is there anything in rye SD that protects the yeasts from salt or it's only a matter of yeast concentration?
What effect does salt have on lactobacilli? especially compared to yeast, I mean: do yeasts suffer more or less than LAB the presence of salt?

Can I conclude that salt has a strengthening effect on the gluten? If it relents protease and amylase activity so much it should permit the dough to undergo a much longer fermentation time; is it correct?

I hope someone can enlighten me ;)

Thanks,
Nico