Sucrose and raffinose in phloem transport

Albert W. Ruesink ruesink at
Tue Nov 6 13:53:11 EST 2001

In response to Carl's question, I'll bet that we're looking at osmotic
impact.  Three times the energy content for every mosmole if we move
raffinose rather than glucose.  Anyone know of any data about this?
                                            Al Ruesink

---------- Forwarded message ----------
Date: 6 Nov 2001 18:23:27 -0000
From: Carl Pike <c_pike at ACAD.FANDM.EDU>
To: plant-ed at
Subject: Re: Sucrose in phloem transport

Some ideas I've heard -
Sucrose is a non-reducing sugar, in contrast to glucose and others
Cells have many enzymes that can react with glucose (thus causing its 
modification or loss en route) whereas invertase is the principal 
enzyme that could react with sucrose.  So, as long as the 
transporting cells don't have invertase, the sucrose can be moved 

I'd be interested in any explanations as to why some plants transport 
larger molecules such as raffinose.

>Dear Plant-edders,
>Is there a good reason why plants transport sugars as SUCROSE in phloem?
>What properties of sucrose make it most suitable as a substance for
>transport of sugar/energy?
>Why would glucose or maltose not be suitable?
>I have this belief that natural selection usually comes up with the most
>efficient solution to the problem.
>John Hewitson
>Dr. John Hewitson
>Science and Plants for Schools (SAPS)
>Homerton College
>Cambridge CB2 2PH  UK
>email: hom-saps at
>Tel: +44 (0)1223 507168
>Fax: +44 (0)1223 215004
>web site:



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