Answer:

Introduction: Photosynthesis is a process in which plants and some bacteria convert light energy into chemical energy, which is stored in the form of glucose. During this process, oxygen is produced which is released into the atmosphere. However, there are some organisms that do not produce oxygen during photosynthesis.

Organisms that do not produce oxygen:

1. Green Sulphur Bacteria: Green Sulphur Bacteria are photosynthetic bacteria that do not produce oxygen during photosynthesis. These bacteria use sulfur compounds instead of water as an electron donor during photosynthesis, which leads to the formation of sulfur instead of oxygen.

2. Nostoc: Nostoc is a type of cyanobacteria that can perform photosynthesis, but it does not produce oxygen. Instead, it produces nitrogen gas during photosynthesis.

3. Chara: Chara is a type of algae that can perform photosynthesis, but it does not produce oxygen. Instead, it produces carbon dioxide during photosynthesis.

4. Cycas: Cycas is a type of gymnosperm that can perform photosynthesis, but it does not produce oxygen. Instead, it produces carbon dioxide during photosynthesis.

Conclusion: Oxygen is not produced during photosynthesis by some organisms such as green sulfur bacteria, Nostoc, Chara, and Cycas as they use different electron donors other than water during the process of photosynthesis.

Green sulphur bacteria use H2S in photosynthesis so it doesn't produce oxygen.