Chlorophyll degradation by free radicals derived from linolenic acid in incubated barley thylakoids

Abstract

SUMMARY Using chloroplasts isolated from the senescent primary leaves of barley seedlings, the linolenic acid‐dependent degradation of chlorophyll was studied in incubated thylakoids. This reaction, measured by the decrease of absorbance at 672 nm, was produced by free radicals from linolenic acid oxidation and, thus, was inhibited by n‐propylgallate and α‐tocopherol, general scavengers of free radicals. Although the beginning of the reaction was delayed by heating the thylakoids, this process must be of a non‐enzymatic nature since it is not impeded by thermal treatment and it proved impossible to isolate a crude extract from thylakoids with a degradative enzymatic activity using a mixture of solubilized chlorophylls as substrate. The enzyme chlorophyll oxidase, described by others for thylakoids, was not found. In addition, the reaction of chlorophyll with the peroxidation products of linolenic acid seems to occur with the cooxidation of one or more carotenoids. Due to the high content of esterified linolenic acid in the thylakoid galactolipids, the degradation of chlorophyll studied here may have a physiological significance.

Lipid production in Dunaliella bardawil under autotrophic, heterotrophic and mixotrophic conditions

“…The lower concentrations of chlorophyll and betacarotene in the presence of glucose in mixotrophic conditions are likely to be related to an increase in the heterotrophic metabolism of glucose (Shihira-Ishikawa and Hase, 1964), and to the destruction of chlorophyll a in response to a decrease in the number of thylakoid membranes in chloroplast (Stadnichuk et al, 1998;Anila et al, 2013). The increase in ROS levels in the presence of glucose seems to cause the chlorophyll degradation (Cuello and Lahora, 1993). Increase in the synthesis of chlorophyll and beta-carotene in D. bardawil (= D. salina) can be due to the presence of acetate, as precursor of acetyl CoA (Murphy and Walker 1982).…”

Drought Stress Syndrome in Wheat Is Provoked by Ethylene Evolution Imbalance and Reversed by Rewatering, Aminoethoxyvinylglycine, or Sodium Benzoate

“…Nevertheless, primary biochemical reactions that affect the metabolism of the whole plant are complex. It has been reported that alterations of photosynthetic membranes and a decrease of the ribosomes and polysomes are the earlier changes provoked by water deficit (Cuello and Lahora 1993, Hendry et al 1987, Thimann 1980. It is known that when leaves are subjected to water stress, the chlorophyll content declines rapidly, and it is more rapid with the stress severity (Baisak et al 1994).…”

Effects of air temperature, photoperiod and leaf age on foliar senescence of western larch (Larix occidentalis Nutt.) in environmentally controlled chambers

“…However, our findings indicate that assimilation rates did not cause lower chlorophyll levels in larch because chlorophyll declined before the decline in photosynthesis under different temperature and photoperiod settings. Instead, the temperature-sensitive process of chlorophyll degradation may involve oxidative damage caused by temperature-induced changes in the membrane (Cuello and Lahora 1993).…”