Stroma, in

botany Botany, also called plant science (or plant sciences), plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "bot ...

, refers to the colorless fluid surrounding the grana within the

chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it ...

. Within the stroma are grana (stacks of

thylakoid Thylakoids are membrane-bound compartments inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen. Chloroplast thyla ...

), and the sub-organelles or daughter cells, where

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

is commenced before the chemical changes are completed in the stroma. Kramer & Scott ''flower'' iv. 80 1979 Photosynthesis occurs in two stages. In the first stage, ''

light-dependent reactions Light-dependent reactions is jargon for certain photochemical reactions that are involved in photosynthesis, the main process by which plants acquire energy. There are two light dependent reactions, the first occurs at photosystem II (PSII) and ...

'' capture the energy of light and use it to make the energy-storage molecules

ATP ATP may refer to: Companies and organizations * Association of Tennis Professionals, men's professional tennis governing body * American Technical Publishers, employee-owned publishing company * ', a Danish pension * Armenia Tree Project, non ...

and NADPH. During the second stage, the '' light-independent reactions'' use these products to fix carbon by capturing and reducing

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

. The series of biochemical

redox Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction ...

reactions which take place in the stroma are collectively called the Calvin cycle or '' light-independent reactions''. There are three phases: carbon fixation, reduction reactions, and ribulose 1,5-bisphosphate (RuBP) regeneration. The stroma is also the location of

chloroplast DNA Chloroplast DNA (cpDNA) is the DNA located in chloroplasts, which are photosynthetic organelles located within the cells of some eukaryotic organisms. Chloroplasts, like other types of plastid, contain a genome separate from that in the cell n ...

and

chloroplast ribosomes A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in t ...

, and thus also the location of molecular processes including chloroplast DNA replication, and transcription/

translation Translation is the communication of the Meaning (linguistic), meaning of a #Source and target languages, source-language text by means of an Dynamic and formal equivalence, equivalent #Source and target languages, target-language text. The ...

of some chloroplast proteins.

References

{{reflist Membrane biology

See also

References