What happens if ph is too low?

Hey I have heard that if ph is too high the leaves can go yellow. But Im just curious...what if ph is too low? What harm can it do to the plant?

thanks for the response

nutrient lockout. here is a table. it shows what nutrients are available at what PH.

thanks for that quick answer mate

no problem. glad i could help.

great post! I've often wondered this myself but always forget to ask.

if that chart is correct (which im sure it is looking all formal as it does!) then what is te reason behind keeping a hydro system between 5 and 6? when all the nutrients are obviuosly better available at 6.5??

Ive always wondered about the different recommended ph's between hydro and soil.

Anyone got any ideas??