plant excretion

[Jon Monroe]

>So, am I still the only one on this list who thinks that plants do have
>to contend with organic metabolic wastes?
>
>Jon Greenberg
>BSCS

I don't think so.  The differences between animals and plants in 
terms of why they produce metabolic wastes and what they do with them 
might be an excellent topic for a Structure Function course like the 
one Kelly McConnaughay mentioned yesterday...

Browsing some of my fact-filled :-), but unfortunately citation-poor 
books, I found that:

According to Raven et al., _Biology of Plants_ 6th ed 1999, 
"Heartwood formation is believed to be a process that enables the 
plant to remove from regions of growth secondary metabolites that may 
be inhibitory or even toxic to living cells" (p. 665).  One could 
also argue that at least some of those secondary metabolites placed 
in the heartwood could function to deter fungal growth and are thus 
not really wastes...

According to Dey and Harborne _Plant Biochemistry_ 1997, in a section 
on vacuoles, "Some storage substances are waste products of the cell 
which have been excreted into the vacuole from the surrounding 
cytoplasm" (p. 11).  Now we can debate the definition of the word 
"excretion"!

Jon

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