The Effect of Water Stress upon Polyamine Levels in Barley (Hordeum vulgareL.) Leaves

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Abstract
The effect of water stress on leaf polyamine content of four Hordeum vulgare varieties, Alger/Ceres, Palmella Blue, Rihane and Roho, with different drought characters was studied After 6 d without water Alger/Ceres, Palmella Blue and Rihane had accumulated putrescine, although only in concentrations up to twice those found in the controls, but Roho had a decreased putrescine content. However, one common response was identified; the accumulation and subsequent loss of putrescine was dependent upon the maintenance and loss of leaf turgor respectively. Consequently varietal differences in putrescine accumulation were related to water consumption rates and the extent of osmotic adjustment. Spermine behaved in a similar manner to putrescine but spermidine levels always decreased. Polyamine levels were never high enough to be an important component of solute accumulation. Proline levels were 150-fold higher and glycine-betaine levels 50-fold higher than polyamines in stressed plants. Proline and glycine-betaine accumulation occurred once a threshold turgor was reached, which in Roho appeared to be a reduction by 0⋅2–0⋅25 MPa or 30–40%. The importance of polyamine accumulation during water stress is discussed.