How do Microwaves Affect Plant Seeds?

By Brett Smith
Close-up of woman holding handful of seeds.

Microwaves are typically used to heat our food or send communication signals, but studies have found that they can also stimulate seed germination and growth.

Promoting Germination

Some types of plants, such as the Acacia, have seeds with a waterproof coating that impedes germination, with the process often taking months or years to unfold. Because of this, those looking to grow them in the nursery have used microwaves to shorten the process, promoting a high final germination percentage and consistent germination after sowing. Using microwaves is considered a dry method for breaking down the seed coating, as opposed to another common method using boiling water. After the seeds have been microwaved, they can be stored for a period of time and remain viable.

Stem and Root Length

Microwaving seeds has also been shown to dramatically increase both stem and root length in some seedlings. However, the seeds should not be microwaved for too long as this will have a negative effect on stem and root length. According to a 2010 study from Agricultural University in Bulgaria, lentil seeds microwaved for 30 seconds at 450 watts had stems that averaged 10 percent longer, and roots that averaged 7 percent longer, compared to control seeds. Seeds microwaved at 60 had stems that averaged 9 percent longer and roots that were 6.5 percent longer, the study found. Seeds in the study were severely negatively impacted by being microwaved for 90 seconds.

Seedling Mass

The Agricultural University of Bulgaria study also revealed that total mass of the seedlings rises with the microwave treatment at 450 watts. At 30 seconds, the total mass was 16 percent higher than the control, and at 60 seconds the total mass was more than 36 percent higher--both measured at 14 days growth. After analyzing higher wattage and longer exposure times, the researchers concluded that microwaving seeds for 30 seconds at 450 watts produces optimal results, with growth stimulation occurring in the later stages of seedling development.

Lower Energy Microwaves

With low-energy microwaves used for communications purposes constantly bombarding us, researchers at the Bhabha Atomic Research Centre in Mumbai, India researched how this radiation might affect germination and growth rate in seeds. The 2011 study revealed that low-power microwaves also had a stimulative effect on seed germination and growth, particularly at the higher microwave power and exposure times used in the study. The study--which included seeds for wheat, bengal gram, green gram, and moth bean--found that the effect of microwaves varied with seed type.

About the Author

Brett Smith is a science journalist based in Buffalo, N.Y. A graduate of the State University of New York - Buffalo, he has more than seven years of experience working in a professional laboratory setting.