MadSci Network: Botany
Query:

Re: why carbon-dioxide supply is not required in plant tissue culure?

Date: Wed Mar 30 20:49:49 2005
Posted By: David Hershey, Faculty, Botany, NA
Area of science: Botany
ID: 1112164877.Bt
Message:

Your question contains a good clue to the answer. If the plant tissue lacks
chloroplasts, then it cannot conduct photosynthesis, which requires carbon
dioxide gas. Plants in tissue culture are given sucrose as their energy source.
Thus, they produce carbon dioxide gas via cellular respiration rather than
consume carbon dioxide gas in photosynthesis.

Production of carbon dioxide via cellular respiration can lower the pH of the
tissue culture medium because of the formation of carbonic acid.  

When a plant cell absorbs more positive ions than negative ions, it excretes
hydrogen ions (H+) to maintain charge balance. The hydrogen ions lower the pH of
the medium. 

When a plant cell absorbs more negative ions than positive ions, it excretes
hydroxyl ions (OH-) to maintain charge balance. The hydroxyl ions raise the pH
of the medium.

The most common tissue culture medium is Murashige and Skoog. It contains a
substantial amount of its nitrogen as ammonium (NH4+) and as nitrate (NO3-).
Therefore, the medium pH can go either way depending on whether the cells absorb
mainly ammonium or mainly nitrate.

References



Re: How do plants alter the pH of a fish tank?


Murashige and Skoog tissue culture medium recipe


Bhatia, P. and Ashwath, N. 2005. Effect of Medium pH on Shoot Regeneration from
the Cotyledonary Explants of Tomato. Biotechnology. 4(1):7-10. 


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