Stress metabolism II. ⋆ Changes in proline concentration in excised plant tissues

Abstract

Shoot apices and excised root systems and sections of the lamina and leaf sheath of the first leaf of to-day barley (cv. Prior) plants were incubated on aerated polyethylene glycol solution (osmotic potential -20 bars) or distilled water. The imino acid proline accumulated rapidly in the leaf lamina sections subjected to osmotic stress and less rapidly, after a delay of 16 hr, in those floated on water. Leaf sheath sections also accumulated proline to a lesser extent, but neither root systems nor isolated shoot apices showed an increase in free proline content on either medium. Leaflamina sections from dark-grown seedlings did not accumulate proline when subjected to an osmotic stress unless supplied with glutamic acid or sucrose. When leaf lamina sections from other dark-grown seedlings were pre-incubated with a mixture of O’IM sucrose and 0'0027M glutamic acid hydrochloride, the subsequent rate of proline accumulation on polyethylene glycol solution approached that in light-grown leaf laminae. Similarly, leaf lamina sections from an albino mutant barley accumulated no proline when incubated on polyethylene glycol solution alone but accumulated proline when the incubation medium was supplemented with glutamic acid hydrochloride and sucrose. In this case the rate of proline accumulation by the chlorotic tissue was considerably less than that of green laminae. The results are discussed in relation to the origin of the proline accumulated in the roots of water-stressed intact plants and the reasons for the differences in proline accumulation potential between the various plant organs. © 1973 CSIRO.