ISTR talk of some plants actually excreting excess salt (NaCl) as one
method of tolerating saline conditions. Also, don't some plants
actively excrete excess water in the process known as "gutation"?

In article .com,
wrote:
Plants do not really produce any solid, organic wastes. The main waste
product of photosynthetic plants in the light is oxygen gas, which
escapes mainly through leaf stomata (tiny pores in the leaf surface).
Water is not really a waste product, it just evaporates from leaves as
a consequence of keeping stomata open to admit carbon dioxide gas
required for photosynthesis.

Photosynthetic plants make all their organic compounds from carbon
dioxide gas, water and mineral nutrients absorbed mainly from the soil
solution. Photosynthetic plants are autotrophs so differ markedly from
animals, which are all heterotrophs. Heterotrophs gets their organic
compounds by consuming other organisms. Heterotrophs have to digest the
other organisms and usually produce some solid waste as a byproduct.

Plants produce a wide variety of organic molecules that do not seem to
play a direct role in their growth and development, such as caffeine,
nicotine, latex, anthocyanins, etc. They are termed secondary
compounds, secondary metabolites or secondary products and are believed
to function mainly in defense against herbivores (animals that eat
plants) or disease organisms. A few secondary compounds are pigments
that color flowers and attract animal pollinators or color fruits and
attract animals that disperse seeds. Red anthocyanin pigments can also
act as "sunscreen" to protect leaves from radiation.

The plant cell vacuole is sometimes considered the "trashcan" of the
cell, and the secondary compounds and inorganic compounds that
accumulate in vacuoles are considered waste. Heartwood, consisting of
xylem that no longer functions in water transport, also accumulates
secondary compounds that are sometimes considered waste. Those views
seem obsolete given the defensive function of secondary compounds.

David R. Hershey

References

The Secondary Metabolism of Plants: Secondary Defence Compounds
http://www.biologie.uni-hamburg.de/b-online/e20/20.htm

Plant Secondary Compounds
http://www.nslc.wustl.edu/courses/Bi.../secondary.pdf

Why Turn Red? The autumn leaf is toast, but it still redecorates
http://www.sciencenews.org/articles/20021026/bob8.asp

Vacuole (plants)
http://www.kcl.ac.uk/kis/schools/lif...ll/vacuole.htm
l


Cheers, Phred.

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LID