A. Aziz et F. Larher, CHANGES IN POLYAMINE TITERS ASSOCIATED WITH THE PROLINE RESPONSE AND OSMOTIC ADJUSTMENT OF RAPE LEAF DISCS SUBMITTED TO OSMOTIC STRESSES, PLANT SCI, 112(2), 1995, pp. 175-186
The relationships between the changes in putrescine (Put) and polyamin
e (PA) contents and proline accumulation induced by osmotic stress wer
e investigated using rape leaf discs (RLD) as an experimental model. T
he aliphatic PAs, Put, spermidine (Spd) and spermine (Spm), were detec
ted in fresh cut RLD and the most abundant among them is Spd. In addit
ion, the HPLC profile of the benzoylated PAs presented an unknown peak
X23 which eluted after that of Spm and did not correspond to any comm
ercially available PAs. X23 occurred also under conjugated forms which
were not destroyed in acidic conditions. The study of the time course
s of the changes in the levels of free PAs, X23 and proline demonstrat
ed that in response to a moderate osmotic shock (-1.5 MPa) enhancement
of PAs was detected after a 2-h lag phase, while the onset of proline
accumulation started 2 h later. When RLD were submitted to wilting or
to increased osmotic stress, using a range of osmotica, they exhibite
d osmotic adjustment which can be associated with an increase in putre
scine and spermidine contents followed by a moderate rise of spermine.
Both free and conjugated PA levels changed. The involvement of these
compounds in metabolic adjustment, as well as their relationship with
proline metabolism under stress conditions, are discussed.