Question
do magnets affect the growth of plants?
and do any plants have iron in them?

Answer
You've heard of Geotropism?

Lie a potted plant sideways and in a few days you'll see the stem growing upwards, the roots growing downwards.  Plants line themselves up in the same direction as the Earth's gravitational field.  Knock them over, and they'll know it's time to switch directions.  That's called 'Geotropism'.

Those who have studied Geotropism have figured out how Plants know which way is up.

Chemicals in all plant cells called 'Auxins' react to Gravity -- the Earth's Magnetic Field.  Auxins order Green cells in the stems and leaves to stretch and grow.  And they order non-Green cells -- the ones in the roots -- NOT to grow.

If you put a plant on its side, Auxins build up underneath the stem and the roots.  That makes the underside grow faster than the upper side; the stem bends.  The same thing happens to the roots; they grow down.

But maybe the plants are responding to LIGHT from above -- NOT GRAVITY, you ask.

No.  It's the Gravity.  This is what makes Trees grow straight up, instead of in an angle toward the Sun.  Plant growth is guided by Geotropism (Gravity) even before they're little plantlets, when they're sprouting UNDERground.  They know just which way to grow even before they've ever seen the light of day.

When scientists want to study the effect of Gravity on plants, they use strong magnets to simulate Gravitational Pull.

One experiment being planned for a NASA Space Shuttle botany project described preliminary work using equipment that featured magnets 'about 50 times more powerful than a typical refrigerator magnet.  The magnets have ferromagnetic wedges attached to them, which focus a strong magnetic field into a small area.'  You can read the whole description here:

http://weboflife.ksc.nasa.gov/currentResearch/currentResearchFlight/sowingSeeds....

So, 'Does a Magnetic Field Affect Plant Growth?'  One inquiring mind named Travis Wallace presented results of his experiment in 2005 at the California State Science Fair:

http://www.usc.edu/CSSF/History/2005/Projects/25475.pdf

After doing his own studies, Wallace concluded that gravity DOES NOT have any effect on Plant growth.

On the other hand, we also have Magnetic Technologies's efforts to answer the same question:

'It is known that Plants and Trees need mineral Salts and microelements from the Soil to function and photosynthesize properly.  However, Plants do not use the majority of nutrients that are in Soil.  While watering Plants with normal Water, only a small amount of nutritional elements dissolves in the Soil and becomes available to the Plants.'  Therefore, they conclude, 'Magnetic Water should be used for irrigation.'  

When people water their potted Plants with 'Hard', non-magnetic Water, they often find a White crust forms over the Soil surface of the soil -- Calcium Bicarbonate.  Using 'magnetized' Water, however, appears to keep those crust-forming deposits away.

So let's go back to Part I of your original question.  Do Magnets affect the growth of Plants?

Answer: We don't know yet.  But we've got evidence.  And we're working on it.

Part II of your question is EASY!

Iron is present in ALL Green Plants.  Because it's used to make Chlorophyll.  Bacteria, people, plants, vertebrates -- most living things need Iron (THE most abundant mineral by weight on the planet) to survive.  As the Green Sea Venture website explains, 'Iron is a micronutrient essential for the
synthesis of enzymes required for photosynthesis.'  Other authorities maintain it is used for DNA production in plants and animals.

Take away a plant's Iron, and suddenly you can't make Chlorophyll.  There's no Iron IN the Chlorophyll, but it's needed to make Chlorophyll.  Short answer: Yes, ALL Green Plants have Iron in them.  On that, there is no question.

Thanks for writing.  Keep in touch.