he leaves of Nelumbo are highly water-repellent (i.e. they exhibit ultrahydrophobicity) and have given the name to what is called the lotus effect. Ultrahydrophobicity involves two criteria: a very high water contact angle between the droplet of water and the leaf surface, and a very low roll-off angle. This means that the water must contact the leaf surface at exactly one, minuscule point, and any manipulation of the leaf by changing its angle will result in the water droplet rolling off of the leaf. Ultrahydrophobicity is conferred by the usually dense layer of papillae on the surface of the Nelumbo leaves, and the small, robust, waxy tubules that protrude off each papilla. This helps reduce the area of contact between the water droplet and the leaf. Ultrahydrophobicity is said to confer a very important evolutionary advantage. As an aquatic plant with leaves that rest on the water's surface, the genus Nelumbo is characterized by its concentration of stomata on the upper epidermis of its leaves, unlike most other plants which concentrate their stomata on the lower epidermis, underneath the leaf. The collection of water on the upper epidermis, whether that be by rain, mist, or the nearby disturbance of water, is very detrimental to the leaf's ability to perform gas exchange through its stomata. Thus, Nelumbo's ultrahydrophobicity allows the water droplets to accumulate together very quickly, and then roll off of the leaf very easily at the slightest disturbance of the leaf, a process which allows its stomata to function normally without restriction due to blockage by water droplets. Thermoregulation An uncommon property of the genus Nelumbo is that it can generate heat, which it does by using the alternative oxidase pathway (AOX). This pathway involves a different, alternative exchange of electrons from the usual pathway that electrons follow when generating energy in mitochondria, known as the AOX, or alternative oxidase pathway. The typical pathway in plant mitochondria involves cytochrome complexes. The pathway used to generate heat in Nelumbo involves cyanide-resistant alternative oxidase, which is a different electron acceptor than the usual cytochrome complexes. The plant also reduces ubiquitin concentrations while in thermogenesis, which allows the AOX in the plant to function without degradation. Thermogenesis is restricted to the receptacle, stamen, and petals of the flower, but each of these parts produce heat independently without relying on the heat production in other parts of the flower. There are several theories about the function of thermogenesis, espec