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Proline accumulation in canola leaf discs subjected to osmotic stress is related to the loss of chlorophylls and to the decrease of mitochondrial activity
Author(s) -
Gibon Yves,
Sulpice Ronan,
Larher François
Publication year - 2000
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.2000.1100407.x
Subject(s) - proline , osmotic shock , malondialdehyde , chlorophyll , chemistry , osmotic pressure , osmoregulation , oxidative stress , osmotic concentration , osmosis , biophysics , biochemistry , horticulture , biology , membrane , salinity , amino acid , ecology , gene
Many stress studies use simplified experimental models like leaf discs, but the validity of such approaches remains a matter of debate, especially when attempts are made to obtain suitable biotests. We report here the analysis of the resistance of canola leaf discs to osmotic stress, as related to the accumulation of proline. For that purpose, the explanted tissues were incubated for 24 h under continuous light and at 28°C on polyethylene glycol solutions of external potentials (Π ext ) ranging from −0.1 to −8.0 MPa. Proline content, water deficit and chlorophyll content were quantified. The cell membrane stability, which is a structural component of viability, was assessed according to electrolyte leakage. Biomembrane oxidative damage was measured through the production of malondialdehyde and the mitochondrial activity was quantified by assessing the ability of the tissues to reduce 2,3,5‐triphenyltetrazolium chloride. Although the water deficit of the tissues reached high values (i.e. up to 70%), the cell membrane stability remained high. Furthermore, the oxidative damage to biomembranes was quite low, even in highly dehydrated tissues. In contrast, osmotic stress induced a significant decrease in the chlorophyll content and a strong accumulation of proline. These two processes each reached a maximum at a Π ext of −3.0 MPa, although the tissues appeared to be viable at even lower Π ext , suggesting they are not responsible for primary resistance. The mitochondrial activity was strongly decreased in the stressed leaf discs, although this activity was at least partially restored in tissues incubated for 24 h on a non‐stressing medium. It appears that the cell components of the osmotic stress resistance assessed observed in this study do not reflect the modes of resistance of an intact plant.