Torana or festoon of fresh mango leaves is an indispensable part in all South Indian Hindu pujas and festivals. Mango leaves are strung on a thread and hung on the doors and windows. The main reason why mango leaf is preferred is that they last longer than other leaves. They are also thick and sturdy. There is no specific symbolic meaning as such.
It is believed that the long life of mango leaves helps it to generate oxygen. And this property of the leaf helps it to absorb carbon dioxide and infuse fresh oxygen. Therefore there is a popular belief that mango leaves are specifically used during pujas and festivals to generate oxygen as large crowd gather during these days in a confined place.
Mango leaves are also used to cover the neck of the Kalash pot used during Puja.