The accumulation of proline in Prasiola crispa during winter in Antarctica

Abstract

Samples of Prasiola crispa were collected in Antarctica throughout a 13‐month period and analysed for free amino acids by HPLC. There was a marked increase in the levels of proline with the onset of winter, concurrent with a decrease in the other predominant amino acids. In January, proline constituted 1.2 ± 0.1 μ mol (g dry weight)−1. whereas by mid‐April it was the major component at 28.4 ± 2.9 μ mol (g dry weight)−1. When winter samples were thawed in a growth cabinet, their proline content declined to 4.3 ± 0.5 μ mol (g dry weight)−1 after 7 days. Measurements of photosynthetic quantum yield indicated that winter samples of P. crispa also recovered photosynthetic activity upon thawing. Amino acids and other solutes are involved in the preservation of photosynthetic activities during freezing and it seems probable that proline is involved in cryoprotection in this species. In summer samples, there was no evidence that proline levels in P. crispa increased with the conductivity of the water in which they were found growing.