The following structures are found on the underside of fern leaves and contain sporangia:
sori
rhizomes
megaphylls
microphylls

The sori are found on the underside of fern leaves and contain sporangia.

Explanation:

Sori are structures on the underside of leaves of ferns. They consist of a variety of sporangia and sometimes a indusium that protects the young sporangias. The shape of the sorus is often of importance when determining a species of fern.

answer: - few nutrients

high pressure

low temperatures

explanation: 1. few nutrients:   open-ocean zone is located way far from the land, which is the main source of the essential nutrients.2. high pressure: pressure increases by 1 atmosphere for every 10 meters increase in depth.3. ample sunlight: a large fraction of the sunlight is reflected back to the atmosphere from the sea surface. 4. varying salinity: below the thermocline, the water is isolated from the atmosphere so the salinity remains stable over the year.5. low temperatures:   the temperature of open-ocean zone ranges from a low of -2°c to an average of 17°c