If you would lose "enough" seeds it would. As it counts as a score drop, same as the loss of acres. However, due to the cap on seeds stolen I doubt you'll ever see it affect the AR mod to any extent.
yup destroying their seeds/plants or stealing them will reduce their score hence if they are solo their ar mod will increase
although it's unlikely that the score drop from the lost seeds will really be big enough to make a meaningful difference to their ar mod, unless of course u got hunting people with massed seeds with chem sprayers and seed theives, that might make a difference.....