Why seeds germinate

Monocots have one seed leaf in the emerging shoot. Once the shoot, with its one or two seed leaves, emerges from the soil or growing media, we call the plant a seedling. Still quite fragile at this stage, the young seedling is vulnerable to diseases and to environmental stresses such as high temperatures and dry soil. Making sure that conditions are optimal for growth will ensure that young seedlings can grow rapidly and uniformly. Seeds purchased within a year of when they are to be planted rarely fail to germinate.

However, seeds are often stored from one year to the next, and if they are stored improperly or for too many years, they can loses vigor and germinate poorly when planted. A simple germination test can show whether or not stored seed is still viable. To test seed for germination, count out a sample of at least twenty-five seeds. Wrap seeds lightly in a moist paper towel, keep the paper towel moist but not soggy for five to ten days.

Unwrap the paper towel and count how many seeds have germinated. We know that seeds need proper conditions to germinate rapidly. Whether seeds are planted into trays in the greenhouse or directly in the field, the goal is to have all seeds germinate close to the same time and grow at the same rate. A uniform tray of transplants or a uniform field of seedlings is easier to manage and will lead to a better crop.

Uneven germination due to slow growth, differences in soil moisture or temperatures, or planting depth of the seed, can result in seedlings of different sizes. This can especially cause problems when transplanting a tray of seedlings; half are ready to plant in the field, and the other half are too small, with root balls that don't slide easily out of the tray cells. In the greenhouse, one way to achieve rapid, uniform germination is to use germination mats under the trays.

These mats allow you to set the temperature according to seed requirements. Make sure you maintain optimal temperatures for your crop see Table 1. Providing good air circulation during germination and early seedling growing will help to control diseases in this early stage.

We cannot control conditions in the field like we can in the greenhouse, but we can still take steps to make sure that seeds planted directly into the field germinate uniformly.

A fine-textured seed bed provides good growing conditions, ample seed-to-soil contact, and the ability to plant to a uniform depth.

Planting when the soil temperatures are near optimum will hasten germination and emergence of the seedlings. Sometimes in the rush of spring planting, seeds are sown in soils that are too cold. This can result in slow germination, weakened and diseased seedlings, and even plant death.

It is much better to delay planting until soils warm up. The optimal temperature for growing seedlings may be different from optimal germination temperatures. Table 2 shows the range of day and night temperatures that are best for growing seedlings in a greenhouse, where temperatures can be controlled.

Cooler temperatures generally slow down growth, and warmer ones speed up seedling growth. All seedlings need ample light to grow. If light levels are low or if seedlings are too crowded as they grow, the stems will stretch as the plants seek more light, resulting in weak, "leggy" transplants.

Consider supplemental lighting if greenhouse light levels are low. The length of time that seedlings need to grow in the greenhouse before they are big enough to transplant into the field varies by crop.

Tomato and pepper seedlings may take five to seven weeks to produce, while cucumbers and squash are ready to transplant after three to four weeks in the greenhouse. But all transplants need to be hardened off before going from the greenhouse out to the field, or they will be damaged by the harsher conditions.

To harden off seedlings, gradually expose them to conditions they will have in the field. Jan 22, The following is how you would cite this page: "How Do Seeds Sprout? Jaze Oct 25, Oct 27, Lily Oct 16, I think this is an excellent article, it taught me a lot about plants! Oct 19, May 1, Hey, Lamya! How did you like this Wonder?

Bobby Tarantino Jun 12, Aug 23, Hello there, jayjay! We hope you're doing well today! Nathalia Oct 26, Hello, Nathalia! It's great that you visited Wonderopolis! May 5, Hi, andy! We're glad you stopped by Wonderopolis! Mar 4, JBOB Feb 25, Feb 26, Very true, JBOB! Thanks for sharing what you learned! Aspen Oct 14, Oct 14, Sep 23, Young's Class Feb 26, We are planting plants in plastic bags to decide which nutrient it grows better in; soil, sun, or water.

We have been studying plants and want to find out how they grow. We are putting the seed with soil in the cabinet to see how long the seed will grow without sun or water. We are going to put a seed by the window without soil or water.

We are going to put a seed in a bag with water, but no sun or soil. Thank you Wonderopolis for reading and replying to our project. Wonderopolis Feb 26, Jan 27, Wonderopolis Jan 28, Nikki May 8, Hi, I am doing a science fair project on plants and this wonder was very helpful.

Thanks a million, Nikki. Wonderopolis May 9, We are so glad that we could help you out! We hope you win a ribbon! Marie Mayo May 8, Wonderopolis May 8, Got to go to bed by the way you are one of the best websites on the Internet in my opinion and my parents love it too. Well got to go goodnight I wonder what the next wonder of the day is bye bye!!!!!!!

This article was very interesting and the video too I loved it sooo much. Moreland's 3rd Grade Class Oct 16, We liked your video so much we watched it twice!

My students thought the seeds looked like a creepy monster! This video goes with our science theme for the month the life cycle of plants and animals. We think tomorrow's wonder will be about Mickey Mouse! Wonderopolis Oct 16, Wonder Friend Aug 3, Great article! We will be linking to this great article on our website. Keep up the great writing. Wonderopolis Aug 4, Wonderopolis May 29, Julie May 27, I once did a experiment with a plant in second grade.

A couple weeks later in second grade, it sprouted. I think it got enough water and enough sunlight for it to grow.

Another time when I'm in 4th Grade, my homeroom planted tomatoes. In a few days, some of the tomato plants sprouted. Wonderopolis May 27, Hector May 23, I loved this one were can I go to find ones related to this one? Wonderopolis May 23, Kyra: May 18, Hey, guys. I love this video. It was funny, even though plants don't grow that fast probably like 30 days or a week, so hope you guys write back even though you always do.

So, bye. Wonderopolis May 18, Wonderopolis May 17, We like it, Colin! Thanks so much for making us smile a little bigger today! Sweet video. I got my mom 30 plants for mothers day and she loves them. It isn't cool to watch plants grow. Where is the excitement? Jazzi May 16, I love watching plants grow. Me and my mom are starting to put plants all the way around my house. Wonderopolis May 16, Wonderopolis May 15, Tavaris Martin Jr May 15, Thank You, This helped me remember the process of a plant's life.

C0Dy May 15, The wonder was actually pretty cool, watching the plants grow from a seed into a plant. It was cool to actually see that. Now that would be cool if plants actually grow that fast, because they would be easier to plant and take care of. Well, the wonder of the day was cool. Zac May 15, I like wonderopolis.

It is full of interesting facts. A May 14, Wonderopolis May 14, The video was amazing, but the article wasn't. Adam May 14, I have a fennel plant in my backyard and it just keeps growing and I don't do anything! Lucky me! Graycee May 14, Dear wonderopolis I think tomorrow's wonder of the day is about Mickey Mouse.

Also, yesterday's wonder what's next was about something that grows in your garden. Miss Greiser's Kindergarteners May 14, We really liked the seed video! We like learning about plants because plants can turn into beautiful flowers. What is the purpose of the petals on the flowers? What kinds of flowers grow the fastest and the slowest? What is the biggest flower? We love plants! I think tomorrow's wonder will be about Mickey Mouse.

Lala May 14, This is a very cool wonder! I wonder what was Wonder 1? Caleb May 14, This reminds me of the time my old class and I put seeds in a bag and taped them on a window and every day checked on it to see if it was growing.

Most plants grow from seeds, which come in a variety of shapes, sizes, and textures. Within this compact package, seeds contain everything a plant needs to grow and reproduce. Some seeds, such as grass, begin life with one leaf. These kinds of seeds are monocots. Other seeds, such as beans, begin life with two leaves. These kinds of seeds are dicots. Emily May 14, I already knew that.

We learned that in 3rd grade. Ms Bayko's class May 14, We thought the plants looked cool when they were growing. The roots looked like worms! Nature is amazing, but we can sometimes take its awesomeness for granted. It seems normal to us, for example, that a seed only a few millimetres in size could become a towering tree.

But have you ever stopped to really think about how, exactly, this seemingly magical transformation actually happens? Like how does a seed take that first step from seed to seedling? Most people learn at school that plants grow by getting energy from the sun via their leaves , and moisture and nutrients from the soil via their roots. But where does a seed get energy and moisture to grow?

Not exactly. Seeds come in all shapes and sizes. Some tropical rainforest orchids have seeds that are smaller than a pinhead—so small,in fact, that they are like dust. At the other end of the scale is the enormous Coco de Mer seed which can be up to 40 centimetres long and weigh as much as 18 kilograms, about the same weight as a medium-sized dog!

In flowering plants, seeds develop in a fruit. The fruit protects seeds but also helps with their dispersal from one place to another. Sometimes the fruit is nice and soft and delicious, like a berry that attracts animals who then accidently carry the seed to a new home.

Other times the fruits are hard and woody, like those of a banksia or eucalypt. This is the Svalbard Global Seed Vault—a seed bank established by the Norwegian government which holds copies of more than 4, plant species from seed banks around the world. The vault holds over 4, plant species including essential food crops such as beans, wheat and rice. The northernmost place in the world with its own airport, Svalbard is the perfect place for the seeds to be delivered from around the world for cold storage.

Even if the power fails, the ambient temperature on this chilly island 1, kilometres beyond the Arctic Circle will keep the seeds frozen without extra cooling. In fact, experiments show that some of the tissues inside of seeds remain active, and even carry out some basic metabolic processes, such as cellular respiration GLOSSARY respiration a chemical process whereby energy is released from glucose.

The embryo gets energy by breaking down its food stores. During aerobic respiration:. Seeds need the right temperature to germinate, and this varies depending on the species of plant and its environment.

Some need fluctuations in temperature. Some need very cold conditions for a few weeks or even months before they will germinate at a higher temperature. This ensures that cold climate seeds, for example, delay germination until after winter. What about light, you might wonder? Such seeds can lie dormant for years, until, say, a tree falls, opening up a gap in the forest canopy and exposing the seed to light.

Interactive How seeds germinate 1 Next Reset. Nearly all seeds are in a sort of suspended animation, called dormancy, until conditions are just right for them to germinate. Dormancy means that, even when exposed to water, oxygen and the right temperature, a seed may delay germination until it gets certain other environmental and chemical cues. A seed may be dormant while still on the parent plant this is known as primary dormancy , or it may become dormant after it has left the parent plant secondary dormancy.

It allows seeds to delay germination until, for example, temperatures are just right for the seedling to thrive. It also means that seeds can wait to become seedlings until they are at a distance from the parent plant for example, by being eaten by animals and excreted elsewhere , which reduces competition with other seeds from the same parent. Dormancy happens through a few different kinds of mechanisms, some of which happen outside the embryo exogenous dormancy , others inside it physiological dormancy.

An example of an exogenous dormancy mechanism is a hard seed coat, which stops the seed absorbing water, and sometimes air. Dormancy may also be triggered by factors inside the embryo, especially chemical changes, which need to occur in the seed before it will germinate. Some seeds, for example, need a period of light or dark to germinate. People working in the agricultural industry will often carry out processes that imitate these natural ones in order to break dormancy and get seeds to germinate—for instance, by chilling seeds to imitate cold weather or by applying abrasives to weaken the seed coat.