Think of a pea seed that you have soaked-the outer seed coat becomes soft and wrinkly with water. The seed rapidly takes up water and the seed coat swells and softens. For these seeds, putting them in the refrigerator for a specific period of time allows them to gain sufficient oxygen and energy to germinate (Colorado Seed Laboratory 2009). Cool temperatures also allow the seed to digest some of its food reserve, giving it energy. Cold temperatures (50-59☏) allow oxygen to get into the seed, while warm temperatures prevent oxygen uptake. For example, the membrane within the seed coat of some seeds forms a barrier that is permeable to water but not to oxygen. To break chemical dormancy, you might have to leach the seed or use cold/moist stratification or fire scarification. Factors affecting seed dormancy include the presence of certain plant hormones-notably, abscisic acid, which inhibits germination, and gibberellin, which ends seed dormancy. Other seeds have internal chemical or metabolic conditions that prevent germination (chemical dormancy). This can be broken by soaking or scarifying (scratching the surface) the seed. Seeds might have a hard or thick seed coat (physical dormancy). Seeds of plants that grow best in the spring have self-selected to germinate only after cold winter temperatures have passed.įor seeds to come out of dormancy, we have to break their physical or chemical dormancy factors. Why would it benefit seeds to not all germinate when conditions are right? In nature, staggering germination keeps some seedlings safe from possible bursts of bad weather or herbivores that might eat them. Seed dormancy is a condition that prevents germination even under optimal environmental conditions. Many seeds have developed a dormancy (or sleep) period. Soil temperatures should be taken by inserting a soil thermometer 3-4 inches deep into the soil surface and noting temperature. Soil temperature conditions for vegetable crop germination. Seedlings will become leggy and fragile and will not produce to their potential if they do not have sufficient light. Don't confuse seed light requirements with what seedlings need. However, some species (e.g., Begonia, Primula, Coleus) need light to germinate (Miles and Brown 2007). Most seeds germinate best under dark conditions and might even be inhibited by light (e.g., Phacelia and Allium spp.). Not all seeds have the same light requirements. ![]() If the soil or media is not well aerated due to overwatering or compaction, the CO 2 will not dissipate and seeds can suffocate. This carbon dioxide needs to be able to move away from the seed. They need oxygen and produce carbon dioxide (CO 2). Seeds respire just like any other living organism. Aeration in the soil media allows for good gas exchange between the germinating embryo and the soil. A fine-textured seedbed and good seed-to-soil contact are necessary for optimal germination. In field soil this is generally about 50-75 percent of field capacity. At optimal temperatures, germination is rapid and uniform.Īll seeds need correct moisture to initiate internal processes leading up to germination. Anything above or below this temperature can damage seeds or make them go into dormancy. The maximum is the highest temperature at which seeds can germinate. The minimum temperature is the lowest temperature at which seeds can germinate effectively. All seeds have optimal temperature ranges for germination (Table 1). Temperature, moisture, air, and light conditions must be correct for seeds to germinate. Seeds Need the Right Environment to Germinate Each seed type has individual needs-take a minute and read about their specific germination requirements. Seeds generally "wake up" and germinate when soil moisture and temperature conditions are correct for them to grow (Miles and Brown 2007). All fully developed seeds contain an embryo and, in most plant species, a store of food reserves, wrapped in a seed coat. They must contain living, healthy embryonic tissue in order to germinate. 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"). Before exploring how to best grow your seeds and seedlings, start with the right seed.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |