Metabolic Aspects of Chilling Resistance: Alanine Accumulation and Glutamate Depletion in Relation to Chilling Sensitivity in Passionfruit Species

Abstract

Changes in the level of different amino acids were measured when the leaves of a number of chilling- resistant and chilling-sensitive Passiflora species were kept at 0°C. An alpine species of Cardamine was used as a reference plant because it is well adapted to temperatures near 0°C. After 48 h at 0°C, alanine levels had increased several-fold in the chilling-sensitive group, while the level of glutamate had decreased several-fold. In the chilling-resistant group there was little change in the level of alanine observable after 48 h, but there was a substantial fall in the level of glutamate. These changes did not occur at higher temperatures. The changes in the levels of other amino acids were small. In leaves of Cardamine, neither alanine nor glutamate levels changed by more than 50%.

Levels of alanine rose about threefold in both chilling-resistant and sensitive species over the first 10 h of chilling. However, while levels continued to rise in the chilling-sensitive species, they had returned to near normal levels by 46 h in the resistant species. The reduction in glutamate was similar for both species; however it occurred more rapidly in the chilling-sensitive species.

It is concluded that chilling-resistance in Passiflora is associated with the ability to prevent a sustained accumulation of alanine at 0°C. It is not specifically associated with the ability to maintain levels of glutamate at 0°C.