In Rhizophora negatively geotropic roots are found, which come above the ground for :-Mechanical support Gaseous exchangePhotosynthesisFloatting

The negatively geotropic roots found in Rhizophora, also known as mangroves, come above the ground primarily for gaseous exchange. These roots, known as pneumatophores, allow the plant to breathe even when submerged in water.

Here's a step-by-step explanation:

1. Rhizophora, commonly known as mangroves, have a unique root system that differentiates them from most other plants.

2. These plants have negatively geotropic roots, meaning they grow upwards, against the force of gravity. These roots are known as pneumatophores.

3. The primary function of these pneumatophores is to facilitate gaseous exchange. Mangroves often grow in waterlogged, low-oxygen soil conditions. The pneumatophores grow out of the water and into the air, allowing the plant to take in oxygen directly from the atmosphere.

4. While these roots do provide some mechanical support, their primary function is not for support or for photosynthesis.

5. The roots also do not aid in floating. The ability of mangroves to survive in waterlogged conditions is due to their unique root system that allows them to breathe, not float.

So, the correct answer is: Gaseous exchange.