Re: How does radiation affect seed growth?

Hi Josh,

You describe an interesting result! (885765703.Ag) I don't know exactly why 
treating seeds with microwave radiation would cause two different plant 
species to germinate faster and grow more poorly than untreated plants, but 
here's some information on seeds you may not know:
Many seeds exhibit dormancy; the seeds will not germinate right away under 
all conditions. Some, like beans and their relatives have a hard 
exterior (seed coat) which prevents the necessary oxygen and water to get 
into the seed. Others either require or benefit from exposure to a cold 
treatment, called stratification (the radish may be affected by cold). 
Others, like lettuce, need light. In the last two cases, it's thought that 
inhibitors in the seed prevent germination until they are removed by cold 
or light. Seed dormancy may be important in controling when the the seeds 
germinate in nature.
For your experiment, you used microwave radiation. This type of radiation 
will heat up any water molecules in the seeds. There isn't much water in 
dry seeds, but the seeds may have heated up slightly. Did you soak the 
seeds in water before treating them? One wouldn't expect that microwave 
radiation would cause mutations (in the DNA) because the wavelength is too 
long and the energy to little. By the way, scientists use X-rays to cause 
mutations in plants. 
My guess is that by heating up the seeds, you have either weakened the seed 
coats (allowing water to more quickly penetrate the seeds)or damaged heat 
sensitive inhibitors). The poor growth following germination may also be 
attributed to heat generated in the seeds by the radiation. Many proteins 
are required for plant growth and development and many are heat sensitive. 
Damaging some of these proteins may have initially crippled the seedling 
causing it to have a slow start, but eventually the treated plants would 
start to grow the same as the control plants since the DNA was probably not 
affected. I hope this helps you with your report and with thinking about 
other experiments!

Rob