In order to absorb the blue color of light in the greatest quantity, the maximum intensity of photosynthesis occurs in red light. So, the correct answer is, ‘Red light’. Note: Chlorophyll is a green-colored pigment that in plants absorbs light for photosynthesis.

White light is the most effective light for photosynthesis because it provides a wide range of colored lights for various pigments to use. When only a single color is used, red is the most effective color of light.

white light

The primary reasons why LED fixtures emit a lot of red are 1) red LEDs are among the most efficient at converting electricity into photosynthetic photons, 2) chlorophyll strongly absorbs red light, thus it is effective at photosynthesis, and 3) red LEDs are relatively inexpensive.

Red light. Maximum photosynthesis occurs in red light. Light is absorbed by photosystem II that is membrane-bound. Hence, some portion of the absorbed light falling under blue is not passed to photosynthesis while all of the red light is absorbed by chlorophyll and effectively used.

light. In contrast, blue light is considered equally effective as green or red light at driving photosynthesis. Thus, while blue light can appear somewhat dim to us, it has high energy and is useful for plant growth applications.

Red light is responsible for making plants flower and produce fruit. It’s also essential to a plant’s early life for seed germination, root growth, and bulb development.

Offering low energy usage, low heat, and color optimized for growth, LED lights are the most efficient, effective, and customer-friendly way to grow plants at home than growing with fluorescent lights or incandescent lights.

Summary. You can use LED lights to start your vegetable seeds indoors and you don’t need special plant grow lights to do so for plants that will eventually be planted outside. If you have a lot of fixtures you can rewire them a few at a time while still gaining the benefits of LED bulbs in all your fixtures.

Vegetable seedlings and other “full sun” plants require about 2000 to 3000 lumens (at minimum) per square foot of growing space. So, if you’re growing just a single standard tray of seedlings, using a grow light that emits 3000 lumens is sufficient. Otherwise, do the math and scale up to a brighter light.

16-18 hours

fluorescent lights

In general, seedlings should receive roughly 14 to 16 hours of light a day when situated in a south-facing window. Many people make the mistake of leaving their seedlings under fluorescent lighting 24 hours a day. This does not make them grow faster, and can actually hinder the success of your seedlings.

Although plants use the full spectrum for photosynthesis, red and blue light seem to be most critical. Red light stimulates vegetative growth and flowering (but if a plant gets too much, it will become tall and spindly).

If you’re growing under lights, adjust them so they’re just a few inches above the tops of the seedlings. Set the lights on a timer timer for 15 hours a day. Keep in mind that seedlings need darkness, too, so they can rest. As the seedlings grow taller, raise the lights.

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.

One easy way to make seeds germinate faster is to presoak them for 24 hours in a shallow container filled with hot tap water. Water will penetrate the seed coat and cause the embryos inside to plump up. Don’t soak them for longer than 24 hours because they could rot. Plant the seeds immediately in moist soil.

Tomato plants don’t seem to suffer any adverse affects from the 24 hours per day treatment. Keep in mind that 24 hour light will significantly speed up growth which could make a seedling get too large for the pot its in and/or be ready to plant outside well before the weather is agreeable.

While leaving growing lights on for a single night is unlikely to have long-term effects on your plants, constantly leaving the lights on can stunt their growth, prevent flowering, cause wilting and burn damage, and may kill the plants.