Some seeds don't need light to break through their seed casings and sprout. Most seeds germinate best with controlled amounts of UV generation, but there are seeds that germinate in the absence of light. Furthermore, there are plants that get enough just light in highly shady areas of a garden or even in darkness.
Most of the seeds germinate best in dark environments. The presence of light tends to inhibit their growth. The light decomposes carbonic acid gas and expels oxygen which leads the seed to harden. These gases are key factors that promote germination.
Different plants have different light intensity needs, but most seedlings grown for the garden will need higher intensity light to flourish. In general, the leaves should be about 2 - 4 inches away from the light source (assuming use of a fluorescent bulb – see below).
They perform important respiratory functions at night. Seedlings should have at least 6 hours of darkness per day, and more mature plants at least 8-10 hours a day.
In case the germination takes place in the darkness, the following consequences will occur: Seeds will not germinate well in absence of light. Light decomposes the carbonic acid gas, and releases oxygen, utilizing the carbon. This causes a hardening of all the parts of the seed, thereby preventing vegetation growth.
Some plants germinate well in darkness, some prefer continuous light, and others have no preference either way.
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.
The answer to this one is simple. Your grow lights should be turned on (or your seedlings should be put under lights) as soon as the first seed starts to sprout. Many types of seedlings grow very fast, and they will begin reaching for the light as soon as they emerge. So give them plenty of it right from the start.
Plants, shrubs and trees use sunlight for photosynthesis during the daytime, but at night they need darkness to regenerate a key compound - phytochrome. Nighttime lighting can reduce vegetation's ability to properly create this compound.
Plant stems become “leggy,” meaning stems become long and thin and appear to be reaching toward the source of light. A lack of sufficient light causes the plant to grow long spaces on stems between the leaf nodes (the point where a leaf grows out from the stem).
The amount of light each seedling needs will vary from plant to plant. Those that require less light at an adult stage don't need as much as those that enjoy full sun throughout their life cycle. Seedlings exposed to too much light or heat will wither and die.
Light intensity can cause severe damage to your seedlings to the point where they die or are stunted.
If your light source is fixed, you can just adjust the height of the trays. Turn the lights on after your seeds have germinated (the exception is lettuce, which needs light to germinate). Seedlings like 12-16 hours of light per day. A timer makes it easy; no remembering to turn the lights on and off.
For many years, fluorescent shop lights were the go-to seed starting bulbs for gardeners, but LEDs have quickly replaced them as the standard choice. LEDs are usually more expensive than fluorescent bulbs, but they are very energy-efficient and long-lasting.
The process of keeping a plant in the dark for a day or two is known as destarching. The plant is kept in the dark for 24-48 hrs. During this time, photosynthesis is halted due to an absence of light. Therefore production of new starch is also stopped.
The light slows stem elongation through hormones that are sent down the stem from the tip of the stem. In the darkness, the hormones do not slow stem elongation. The seeds in the dark-grown condition rely upon the stored chemical energy within their cells (lipids, proteins, carbohydrates) to power their growth.
A: In general, you should not leave grow lights on 24/7. Plants need a light-dark cycle to develop properly. It's believed that they truly do “rest” during periods of darkness, and probably use this time to move nutrients into their extremities while taking a break from growing.
Seeds don't need light in order to sprout. Steady warm temperature is more important for sprouting, such as that provided via a seedling heat mat. So, you technically don't need to turn your grow lights on until after they emerge from the soil.
All seeds need water, oxygen, and proper temperature in order to germinate. Some seeds require proper light also. Some germinate better in full light while others require darkness to germinate.
Seed germination (or seed starting) is the process of growing plants directly from seeds instead of buying ready-grown plants. Sprouting seeds indoors is an effective way to increase the germination rate versus germinating seeds outdoors directly in the soil.
Seeds need to be moderately moist to sprout. Seed germination is highly dependent on watering. Too dry and they won't get the message to sprout, too wet and they will rot in the dirt.
It is true that seedlings need lots of bright light to grow healthy and strong—but they also need a period of darkness in order to thrive.