House plants have most of the same basic needs that humans have. Air, water and nutrition to name the basics. Plant nutrition is a balance of minerals and vitamins that can be species specific, but there is a broad level of these compounds that create a good balance for plant life. The scientific evidence has been presented that plants synthesize vitamins and there are direct usages that benefit plant health.
Just as in humans, antioxidants protect cells against free radicals, negative byproducts found in the environment and air. Free radicals can mutate cells and are a leading cause of cancers and disease. Vitamin B-12 has a hand in regulating radical transfer reactions, but is not present in land plants. Algae uses B-12 or cobalamin is required for methionine synthase.
Thiamine for Growth
Thiamine or Vitamin B-1 plays an important part in plant metabolism. It helps prevent transplant shock and gives tiny new roots a jump start. B-1 is produced in a plants leaves and the vascular system transports it down to help roots and develop them. It is often applied to stressed plants since it is assumed the plant is not producing sufficient B-1.
Riboflavin and Pyridoxine
Riboflavin is synthesized in house plants and is an important factor in metabolism of carbohydrates and amino acids. Pyridoxine serves much the same purpose but is a cofactor in the enzymes that metabolize carbohydrates and aminos. It is known as Vitamin B-6.
Vitamin C is present in plants as ascorbate and is an important antioxidant. House plants can intake and utilize these vitamins to protect their cells against toxins. Vitamin C also has a role in cell production, stem growth and is needed to produce proteins that build cell walls.
Vitamin bio-synthesis has become an important area of study. It can help identify which and how much of the vitamins are needed for healthy plant growth. It is also verifying how plants use vitamins and how they acquire them. In the home, the application of vitamin mixtures is standard, since most all-purpose plant food has some vitamin elements in them. It is possible to dilute a multivitamin and water your plant with it. There will probably be increased health and growth depending on the variety. The student project "Will Vitamins Affect Plants," on the Miniscience website, showed that the vitamins did increase vigor and growth.