Subject: why is there a difference in amount of DNA extracted

I extracted DNA from peas (yellow, green, chick), wheatgerm, onion (purple, 
white), leek (bulb, root, leaves), kiwi, banana, parsnip, parsley, kale. The 
kiwi, parsnip had the most DNA, the kale, leek roots, parsley the least DNA. 
Why? How would I determine how many cells each source had or the amount of 
water (which would lead to less DNA extraction). I used ice cold alcohol but 
now will vary the temperature of it -- will warmer alcohol be less dense. 
Thanks for your help.

Re: why is there a difference in amount of DNA extracted