Using any fertilizer not designed specifically for indoor plants can be harmful, because they add too many salts into the soil causing the roots to burn.
because fertilizers are rich in nutrients
No, But vegetables contain vitamins as well as many other needed nutrients.
Artificial fertilizers are used and needed for a number of reasons. These fertilizers help meet the deficit made by real fertilizers.
Apples contain many nutrients that are needed for a healthy and well-balanced diet. These nutrients include flavonols, catechins, anthocyanin's, chlorogenic acid, phloridizin, and many other polyphenol nutrients. Apples also contain Vitamin C and fiber pectin.
Nitrogen [N], phosphorus [P], and potassium[K] tend to be the nutrients that are found in fertilizers. Nitrogen encourages proper root growth. Phosphorus encourages proper shoot growth. Potassium encourages proper fruiting and flowering, and promotes overallplant health.
Light is needed because the sun's rays contain nutrients that the plant needs to grow.
Simple plant fertilizers combine N, P and K; nitrogen, Phosphorus, and Potassium. These are the elements most needed by plants. There are many more elements needed and more complex fertilizers are available for this. In particular, some soils are deficient in 'trace elements' such as selenium, but these tend to be of local importance.
In addition to sunlight, CO2 and water, plants need certain elements in order to produce the compounds that they require to live. The most needed are nitrogen, phosphorus, and potassium. There are a number of others. Fertilizers are an attempt to replace these elements into the soil so that plants can grow faster than they would if you waited for nature to replenish these things "normally" (mainly by decay). But if you add to much fertilizer then the plants can get "burned" and will lose productivity. Also Nitrogen, Phosphorus and Potassium are macro nutrients.
Protein (amino acids)
Protein (amino acids)
Different fruits contain different vitamins. The rule of thumb is to eat different coloured fruit and veg because the pigments contain different nutrients.
Fertilizers provide the nutrients which plants need. The principle ones are nitrogen, phosphorus and potassium. Nitrogen is needed to make proteins, phosphorus is needed for nucleic acids, and potassium has many roles including controlling the opening and closing of stomata. Intensive gardening and agriculture often remove these nutrients from the soil.