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Function of leaf hamamelitol as a compatible solute during water stress treatment of Hedera helix L.
Author(s) -
MOORE B. d.,
TALBOT J. N.,
SEEMANN J. R.
Publication year - 1997
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.1997.d01-130.x
Subject(s) - hedera helix , compartmentalization (fire protection) , vacuole , sugar , cytoplasm , sucrose , botany , apoplast , biology , osmotic shock , chemistry , horticulture , biochemistry , cell wall , gene , enzyme
ABSTRACT 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 14 CO 2 in leaves of H. helix , but is very long‐lived (estimated t 1/2 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.