ISSN:
1365-3040
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Hamamelitol is an unusual branched-chain sugar alcohol previously suggested to function as a leaf compatible solute. In this study, we have examined the leaf metabolism and intracelluiar compartmentalization of hamamelitol and other soluble sugars during long-term water stress treatment of Hedera helix (English ivy). Total leaf hamamelitol content was relatively low in greenhouse control plants, but increased 2-fold during water stress treatment to levels approaching those observed in field-grown plants (6–7 μmol g−1 fresh weight). Using density gradient fractionation with non-aqueous solvents, we showed that hamamelitol occurs primarily in the cytoplasm and vacuoles of leaf mesophyll cells. During water stress treatment most of the increase in leaf hamamelitol occurred in the mesophyll cytoplasm, compensating osmotically for a decrease in cytoplasmic sucrose concentration. The maximum concentration of cytoplasmic hamamelitol was 155 mol m−3 and occurred in field-grown plants. Labelling experiments showed that hamamelitol is slowly synthesized from 14CO2 in leaves of H. helix, but is very long-lived (estimated t1/2 of 4 years). Together, these data indicate that hamamelitol probably functions during long-term stress conditions as an osmotically active, compatible solute in plant leaves. We suggest that the signal for enhanced accumulation of hamamelitol during the water stress treatment was initiated by decreased plant growth and increased leaf sucrose hydrolysis.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1365-3040.1997.d01-130.x
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