Plants have pores (called stomata) under their leaves used in perspiration which also regulates the temperature of their body. Water is absorbed by the roots and eventually perspires through the stomata under its leaves. The stomata can be opened and closed at will. When the all the stomata close the leaves will tend to curl. A plant would only curl like this in the event of intense light, heat or low water availability. Try cooling the plant down, watering it and moving it into the shade or reposition light positioning.
Some other problems could include:
- Insect damage: Aphids, thrips, and whiteflies can cause leaves to curl by sucking the juices from new leaves.
- Heat or wind stress: Leaves that curl upwards may indicate heat or wind stress.
- Root problems: Leaves that curl downwards may indicate problems with the roots. You can check for root rot and repot in fresh soil if needed.