how does the seed absorb water at the time of germination?
Answers
Seed and Seedling Biology
Photo credit: bigstockphoto.com
Choosing the Right Seed
Before exploring how to best grow your seeds and seedlings, start with the right seed. If you intend to run your operation as certified organic, you are required to use certified organic seed and seedlings with only a few exceptions (see the "Organic Requirements").
What Do Seeds Need to Germinate?
Viable seeds are living entities. They must contain living, healthy embryonic tissue in order to germinate. All fully developed seeds contain an embryo and, in most plant species, a store of food reserves, wrapped in a seed coat. Seeds generally "wake up" and germinate when soil moisture and temperature conditions are correct for them to grow (Miles and Brown 2007). Each seed type has individual needs--take a minute and read about their specific germination requirements.
Seeds Need the Right Environment to Germinate
Temperature, moisture, air, and light conditions must be correct for seeds to germinate. All seeds have optimal temperature ranges for germination (Table 1). The minimum temperature is the lowest temperature at which seeds can germinate effectively. The maximum is the highest temperature at which seeds can germinate. Anything above or below this temperature can damage seeds or make them go into dormancy. At optimal temperatures, germination is rapid and uniform.
All seeds need correct moisture to initiate internal processes leading up to germination. In field soil this is generally about 50-75 percent of field capacity. A fine-textured seedbed and good seed-to-soil contact are necessary for optimal germination. Aeration in the soil media allows for good gas exchange between the germinating embryo and the soil. Seeds respire just like any other living organism. They need oxygen and produce carbon dioxide (CO2). This carbon dioxide needs to be able to move away from the seed. If the soil or media is not well aerated due to overwatering or compaction, the CO2 will not dissipate and seeds can suffocate.
Not all seeds have the same light requirements. Most seeds germinate best under dark conditions and might even be inhibited by light (e.g., Phacelia and Allium spp.). However, some species (e.g., Begonia, Primula, Coleus) need light to germinate (Miles and Brown 2007). Don't confuse seed light requirements with what seedlings need. All seedlings require sunlight. Seedlings will become leggy and fragile and will not produce to their potential if they do not have sufficient light.