Short-term treatment of potato tuber (Solanum tuberosum L.) dises with CdCl₂ (1mM) induced an oxidative stress, manifested by higher levels of H₂O₂, and activated the synthesis of phytochclatins ((γ-Glu-Cys)n-Gly): PC₂, PC₃ and PC₄. If in the tissues with a lower GSH level, the oxidative stress was induced by treatment with 3-aminotriazol (AT), or with AT and H₂O₂, the elevation of H₂O₂ and GSH levels and then some accumulation of thiols, including PC₂, PC₃ and PC₄, were observed. However, this increase of PC concentration was considerably lower when compared with the effects brought about by Cd⁺² treatment. If such a procedure of evoking subsequent moderate oxidative stress in tissues preceded Cd-treatment, a marked limitation of PC synthesis was observed. The presented results support the role of H₂O₂ as the second messenger in activating GSH synthesis and thus suggest a possibility of redox type regulation mechanism of PCs synthesis.
Genotype-dependent variation in water stress-induced tissue dehydration (RWC), proline accumulation (PA), membrane injury (MI) and stress resistance (R) was studied among old and modern cultivars of winter wheat (Triticum aestivum L.). Twenty-day- old seedlings grown in nutrient solution were subjected to a moderate water stress (-0.75 MPa) by immersing (for 72 h) their root systems in aerated nutrient solution with the addition of polyethylene glycol (PEG 6000). Both cultivar groups tended to exhibit a different responsibility to the moderate stress. Water deficit induced reductions in the water content of leaves in five out of nine modern cultivars only and in these cultivars an increased accumulation of free proline was found. The highest, about 100-fold increase in PA was noticed in the modern cvs Emika and Finezja. The highest MI (≈ 12%) had the modern cv. Finezja. The leaf PA under stress positively correlated with MI, but both characteristics showed negative correlations with RWC. Only weak and insignificant relationships between leaf characteristics and stress resistance were observed. The results suggest that none of the individual measured physiological parameters would indirectly serve as a precise indicator for drought resistance in the studied wheat collection.
The paper presents a procedure to identify promising, chilling-insensitive cucumber genotypes from a pool of 55 breeding lines. Selected genotypes may constitute valuable material in further selection of high-yielding cultivars in moderate climate. The approach is based on determining nitrate (NO3–) content, nitrate reductase activity (NRA) and chlorophyll content (Chl) in cotyledons of cucumbers grown at 12℃. These observations were then used to develop a simple algorithm, which facilitates the ordering of genotypes according to their chilling sensitivity by assigning them ranks on the basis of quartile values (from 1 to 4) of determined traits. From the examined collection, 14 least chilling-sensitive genotypes were selected, i.e. their selection for further breeding carries the lowest risk. Low chilling sensitivity of the above mentioned 14 cucumber genotypes was manifested by high Chl levels and high NRA as well as high NO3– contents, i.e. the sum of quartile ranks ranged from 10 to 12, at a maximum of 12. Then cluster analysis was applied to select genotypes, which possess desirable levels of tested traits. Cluster analysis showed that at the division into two and into three subsets all the 14 genotypes considered promising were found within the same cluster, when these genotypes were divided into more subsets, 13 out of the 14 best genotypes were found in one cluster. The presented method may be used to select the least chilling-sensitive cucumber genotypes also from other collections. Knowing the quartile values calculated on the basis of presented results, the rank of new genotypes characterizing their chilling sensitivity may be estimated, provided that experiments are carried out under conditions similar to those used in this study. Otherwise the application of this algorithm has to be preceded by an in-depth explorative analysis and the determination of new quartile values for the analyzed traits.
The formation of insoluble wall bound proline-rich proteins (PRPs) and hydroxyproline- glycoproteins (HRGPs) in relation to the growth stage and developchanges was examined in red raspberry primocane cortex. Two cultivars _ Latham' and 'Malling Promise' - differing in growth intensity and in sensitivity to biotic stress were used for the experiments. The level of insoluble cell wall bound ,c the cortical tissues was almost similar in the course of the plants growth ; HRGPs were significantly higher at the end of the vegetation season (August r), especially in 'Malling Promise'. ,e plant sensitivity to biotic stress, based on the response to the fungus Didymella aplanata changed in the period of vegetative growth. At the end of summer the 'vars became more resistant. It has been inferred that the insolubilization of wall PRPs and HRGPs was responsible for the acquiring resistance to D. applanata by 'Malling. Promise', which was previously very susceptible to this fungus.