Answer:
Blue light
Adding 10-20% blue light allowed plants to grow much healthier, with a compact appearance. There is also far-red light which is has wavelengths that are lower than normal red light–similar to near-infrared wavelengths. Far-red light helps the plants produce greater yields.
Different: in covalent bonds, atoms share electrons, whereas in ionic bonds atoms transfer electrons.
Alike: Both ionic and covalent bonding lead to the creation of stable molecules.