Environmental stress impacts cause an increased formation of reactive oxygen species (ROS) in the chloroplasts (photo-oxidative stress). The role of glutathione in the antioxidative defence system provides a rationale for its use as a stress marker. However, responses of glutathione concentrations and redox states are not consistent among the large number of available publications. In the present review the hypothesis that stress responses of the glutathione system follow a general ecophysiological stress-response concept is investigated. In this view, an initial response phase would be followed by an acclimation phase where a new steady-state is established. Alternatively, if successful acclimation is not achieved, degradation of the system will follow. Recent publications dealing with responses to photochilling, salinity, and drought are analysed as to whether the results fit the concept. In general, an initial stress response was related to changes in the glutathione redox state, whereas acclimation was marked by increased glutathione concentrations, increased related enzyme activities, and/or a more reduced redox state of glutathione. The latter was interpreted as overcompensation leading to enhanced regeneration of glutathione. Deterioration effects upon strong stress impacts were related to progressive degradation and oxidation of the glutathione pool. A time-course analysis, which has rarely been done in the published literature, showed this sequence of events. When apple trees were subjected to progressing drought, the initial response was a slight oxidation of the glutathione pool, followed by increased glutathione concentrations. When the stress increased, glutathione concentrations dropped and redox state became more oxidized, which marked the degradation of the system. In spite of the general congruency of these results with the suggested stress-response concept, several limitations have to be highlighted: The importance of the glutathione system relative to other components of the photoprotective and antioxidative defence system, as well as relative to stress avoidance strategies, has to be established. It is suggested that a variety of parameters taking into account alternative protection pathways (e.g. photorespiration, light dissipation) and other components of the antioxidative systems should be measured. Within such response patterns the glutathione system is a valuable stress marker in ecophysiological studies.

Eleven organically grown apple cultivars and 11 apple cultivars of integrated production from Austria and Slovenia were analyzed by HPLC for the content of phenolic compounds in peel and pulp. We identified chlorogenic acid, p-coumaric acid, procyanidin B3, protocatechuic acid, (−)-epicatechin, phloridzin, rutin and quercetin-3-rhamnoside in apple peel. In apple pulp, (+)-catechin was also identified in all the cultivars. Some other phenols (procyanidin B3, rutin and quercetin-3-rhamnoside) could not be identified or were not properly separated. With regard to the phenolic content in the apple peel, there were no differences between organically grown apple cultivars and apple cultivars of integrated production. Organically grown apples, however, exhibited a higher content of phenolic substances in the apple pulp compared with the apple cultivars of integrated production. This may be due either to the different genotype source or to the growing technology. Higher concentrations of phenolic compounds in organically grown cultivars could be a result of plant response to stress. The apple peel contained higher concentrations of identified phenols than the pulp. The apple peel represents up to 10% of the whole fruit; therefore the phenolsic compounds in the pulp are of greater importance to the consumer than the phenolic compounds in the peel.

In spruce (Picea abies) needles gatath nead gutathioe reductase show a periodic seasonal variation with sig ca increased levels during the winter. It is proposed that gutathione and gIutathione reductse play an important role for the winter hardiness of leaves from evereen plants.Glutathione reductase (EC 1.6.4.2) converts GSSG2 generated by various nonenzymic and enzymic (i.e. dehydroascorbate reductase) reactions back to the reduced form GSH. This enzyme provides that the GSH/GSSG status of the cells is mostly in the form of GSH with only minute amounts of GSSG present. One of the main functions of GSH in plants is to protect -SH groups in enzymes and structural proteins against oxidation either by acting as scavenger for oxidizing substances or by repairing the -SH groups via the GSH-disulfide exchange reaction. The GSSG formed in both cases is reduced rapidly by the action of GR (3). According to the -SH hypothesis of Levitt (6), freezing tolerance in plants involves an increase in the resistance toward oxidation of -SH groups in proteins. Thus no formation of S-S bonds takes place when the photoplasma is progressively freeze-dehydrated. This theory, however, supposes that an effective system is operating in the leaves of frost-resistant plants (for instance spruce needles) which maintains the -SH containing proteins in the reduced state during the frost period. The results presented in this paper suggest that GSH and GR play an important role for the winter hardiness of spruce needles as both significantly increase during the cold period. MATERIALS AND METHODSPreparation of Enzyme Solution. The acetone dry powder of 2 g of needles (2) was shaken in 40 ml of 67 mm KH2PO4/ Na2HPO4 (pH 7.4) containing 1 mm EDTA for 1 hr. Plant Physiol. Vol. 61, 1978 earlier (5) that the main low mol wt thiol in spruce needles is GSH which usually comprises more than 95% of the total nonprotein sulfhydryl compounds. Depending on the needle age its concentration may range from 0.07 to 0.70 jumol/g fresh wt (Tables I and II). Cysteine was found to be present only in small quantities with a concentration mostly below 0.01 ,umol/g fresh wt except in April when cysteine rose for a short period up to 0.125 A.mol. As shown in Tables I and II the GSH content of needles of the same age is rather independent of

Objective: This study was carried out to obtain data about the sugar-, acid-and phenol content of apple cultivars from organic and integrated fruit cultivation, with reference to their role in human health and especially for diet recommendations. Setting: Styria (Austria) and Slovenia. Interventions: HPLC, Spectral Photometry, organoleptic and olfactory tests. Results:The total sugar content of most cultivars from integrated cultivation ranged between 115 and 160 g/kg. Some cultivars from organic growing reached higher values. The acid content of both cultivar types was similar. The phenol content in organically grown cultivars was much higher than that of the ones from integrated cultivation. Conclusion: Knowledge of the sugar content is very important for diabetic patients, owing to the assumption of general diet recommendations that 100 g fruit contain 12 g carbohydrates. This applies to most well-known cultivars like Golden Delicious or Gala, but not to most of the regional cultivars. For diabetics, it is necessary to know the carbohydrate content of food precisely, in order to adapt the amount of insulin to the ingestion. So, it is helpful to know the sugar content of each regional cultivar. Moreover, very high levels of phenolic compound in organically grown cultivars, and with it its importance for human health leads to the recommendation to eat regional fruits from organic fruit growing instead of those grown under integrated cultivation.

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