Ece Turhan

Changes of Micronutrients, Dry Weight, and Chlorophyll Contents in Strawberry Plants Under Salt Stress Conditions*

Abstract Various concentrations of NaCl (0, 500, 1000, and 2000 mg/L) were applied to plants of the “Camarosa” and “Tioga” strawberry varieties for 10 weeks. At the end of the experiment, it was determined that the leaf dry weight increased especially at 500 and 1000 mg/L NaCl treatments when compared to control treatment. However, salt applications did not change total chlorophyll content. With the salt applications, iron (Fe) and manganese (Mn) content increased, while copper (Cu) content did not change in the aerial part of plants in both varieties. On the other hand, zinc (Zn) content increased in the “Tioga” strawberry variety. In the root part of plants, Fe, Zn, Mn and contents did not change according to salt applications in both strawberry varieties. However, 2000 mg/L NaCl of salt applications increased Cu content in the “Camarosa” strawberry variety significantly. *This study is part of the Ph.D. thesis project supported by Uludag University Research Foundation as project no. 2000/24.

Effects of Sodium Chloride Applications and Different Growth Media on Ionic Composition in Strawberry Plant

Abstract The effects of salt (NaCl) applications of various concentrations (0, 500, 1000, and 2000 mg/L) for 10 weeks (69 days) on the morphologic properties and ionic composition of the “Camarosa” strawberry variety grown in perlite and perlite : zeolite (1:1) media were investigated. Injuries of varying severity appeared in the plants depending on the increase of NaCl concentration. At the end of the salt applications, in the aerial part of the plants, the amounts of sodium (Na), chlorine (Cl), calcium (Ca), and magnesium (Mg) had generally increased, while the amount of potassium (K) and phosphorus (P) had decreased. In the roots of the plants, salt applications increased the amount of Na and Cl and decreased the amount of K and Mg; however, they did not change the amount of Ca and P. In addition, in the aerial parts of the plant, the amounts of Ca and Mg were higher in the perlite : zeolite (1:1) medium than in the perlite medium generally. It was observed that in the roots, the amount of K was higher in the perlite medium, whereas the amount of Mg was higher in the perlite : zeolite (1:1) medium. It was determined that 500, 1000, and 2000 mg/L NaCl levels caused osmotic effects in the “Camarosa” strawberry variety. Moreover, they possess the ability to bring about osmotic regulation. #This study is part of the Ph.D. thesis project supported by Uludag University Research Foundation as project no. 2000/24.

Apoplastic anti-oxidants in pepper (Capsicum annuum L.) fruit and their relationship to blossom-end rot

Summary The aim of the present research was to study changes in the major anti-oxidative enzyme activities known to be associated with the apoplast, during the induction of blossom-end rot (BER) in bell pepper (Capsicum annuum L.) fruits grown under saline conditions. Pepper plants of the BER-sensitive cv. ‘Mazurka’ and less-sensitive cv. ‘Selica’ were grown under control, low- and high-salinity irrigation regimes. Fruits were harvested continuously and, after approx. 7 months under these conditions, BER symptoms started to appear (in the Spring season) and fruits were sampled for biochemical measurements. The intercellular washing fluid (IWF; apoplast fraction) of the fruit pericarp was prepared and enzyme activities in that fraction were determined. The results showed that production of reactive oxygen species (ROS) in the fruit apoplast was higher in ‘Mazurka’ than in ‘Selica’. Apoplastic peroxidase and superoxide dismutase (SOD) activities, and the concentration of ascorbic acid, increased during ‘Selica’ fruit development, whereas the concentration of H2O2 decreased. During the stage of rapid growth, when fruits are most susceptible to BER, apoplastic peroxidase activity was greatly enhanced in the healthy pericarp of BER-affected fruits compared to healthy fruits. Under saline conditions, apoplastic peroxidase and SOD activities, as well as ascorbic acid and H2O2 levels, increased in healthy fruits of the resistant cultivar ‘Selica’; whereas, in healthy fruit of the BER-sensitive cultivar ‘Mazurka’, apoplastic peroxidase activity decreased while the level of ascorbic acid increased, but to a much lesser extent than in ‘Selica’. SOD activity and H2O2 levels increased similarly in both cultivars with increasing levels of salinity. It is proposed that apoplast-associated peroxidase activity and ascorbic acid concentration are increased coordinately in response to salt stress and may be part of a protective anti-oxidation mechanism that determines cultivar sensitivity to BER.

Changes in peroxidase activities and soluble proteins in strawberry varieties under salt-stress

Effects of salt stress on the activity of peroxidase (PRX) isozyme and leaf proteins were studied in the three strawberry varieties, Camarosa, Tioga and Chandler. Plants were watered with modified 1/3 Hoagland nutrient solution containing 0 (control), 8.5, 17.0 and 34.0 mM NaCl for 30 days fallowing 20 days acclimation. PRX activity was assayed in leaf extracts and PRX profiles of control and salt treated plants were performed by native polyacrylamide gel electrophoresis (PAGE). During the salt stress Tioga and Camarosa tolerated the cellular damage with less electrolyte leakage while Chandler exhibited a severe cellular damage with the highest (87.5 % in 34.0 mM NaCl treatment) electrolyte leakage. Total soluble protein content was decreased by salinity in Tioga (from 11.35 to 5.86 mg g−1 DW) and Chandler (from 9.35 to 3.90 mg g−1 DW) while it was almost unchanged in Camarosa. Salt stress increased total and specific PRX activity as compared with the control in all the varieties. In native PAGE, one basic isoperoxidase band (Rf=0.27) was observed commonly with different band intensity in all the treatments. Therefore, it might be associated with lignification and recovery of cell membrane damage in strawberry plants under salt stress.

Changes in ascorbic acid concentration, ascorbate oxidase activity, and apoplastic pH in relation to fruit development in pepper (Capsicum annuum L.) and the occurrence of blossom-end rot

Summary We recently suggested that the occurrence of ascorbic acid (AsA) in the apoplast of bell pepper fruit may be part of the protection mechanism against blossom-end rot (BER). In the present study, we determined AsA concentrations, changes in pH, and the activities of ascorbate oxidase (AO) in the apoplast and symplast of pepper fruit, in relation to fruit development and the occurrence of BER. In healthy pepper fruit, the concentrations of AsA in the symplast and apoplast increased during fruit development, whereas the activity of AO decreased when measured at the pH typical of each developmental stage. The apoplastic pH decreased from 6.2 in young fruit to 4.8 in mature red fruit; while the symplastic pH did not change during fruit development. Following high-temperature treatment (35°C for 48 h in the dark), the concentration of apoplastic AsA, and the activity of galacturonic acid reductase (which participates in the AsA biosynthetic pathway), decreased, while there was an increase in apoplastic pH. The AsA content decreased in the apoplast of BER-affected fruit, and the pH was more alkaline (pH 6.9) than in healthy fruit (pH 6.0). In young fruit with BER, the apoplastic AO activity increased and the symplastic galacturonic acid reductase activity was inhibited. We suggest that a reduction in apoplastic AsA concentration, an increase in apoplastic AO activity, and changes in apoplastic pH in fruit prone to BER may be part of the mechanism which leads to the occurrence of BER symptoms. Whether or not there are causal relationships between these changes is not yet clear.

Blossom-end rot is associated with impairment of sugar metabolism and growth of pepper (Capsicum annuum L.) fruits

Summary Blossom-end rot (BER) in pepper fruits is known as a “physiological” disease which is evoked by climatic and osmotic stresses (e.g., high temperatures and salinity) and by deficit irrigation management. The physiological and biochemical mechanisms involved in the stimulation of BER are still a matter of dispute. It has been proposed that BER occurs under cultivation conditions that accelerate fruit growth beyond calcium supply to the growing tissue. In the present study, we investigated this hypothesis by recording fruit growth and sugar metabolism under normal and BER-inducing conditions.The results showed that pepper fruits grown in a ventilated-cooled greenhouse, which ameliorated BER, had a higher initial growth rate than those grown in a non-cooled greenhouse, but had lower calcium concentrations in the fruit pericarp. Fruits that grew without ventilation-cooling had higher concentrations of apoplastic and symplastic sucrose and reducing sugars, and higher levels of symplastic starch than those that developed in a cooled greenhouse. Concomitantly, fruits that developed in a non-cooled greenhouse had lower acid invertase, sucrose synthase and fructokinase activities than those that developed in a cooled greenhouse. Accordingly, the non-necrotic part of BER-affected fruits had higher concentrations of symplastic starch, reducing sugars and sucrose than healthy fruits. These findings indicate that the occurrence of BER in pepper fruits was associated with impaired sucrose metabolism in fruit tissues, which led to reductions in growth rate and final size. Thus, the present findings negate the notion that BER occurs when fruit growth rate is stimulated, and favour the idea that direct impairment of fruit sugar metabolism and of normal fruit growth are involved.

Soluble Sugars and Sucrose-Metabolizing Enzymes Related to Cold Acclimation of Sweet Cherry Cultivars Grafted on Different Rootstocks

The bark tissues were collected from 4-year-old sweet cherry trees cvs. 0900 Ziraat and Lambert grafted on Gisela 5 and Mazzard rootstocks in cold-acclimated (CA) and nonacclimated (NA) stages. Bark tissues subjected to 4°C and −5°C injured to a limited extent in both stages. However, more than 50% injury occurred by temperatures equal to or colder than −15°C only in NA period. Total soluble sugar (TSS), reducing sugars, and sucrose contents were higher in CA than those in NA stages in all samples. The activities of acid invertase (EC 3.2.1.26) and sucrose synthase (SS) (EC 2.4.2.13) enzymes were higher in NA stage than those in CA stage. Considering the rootstocks, reducing sugars were higher in both cultivars grafted on Gisela 5 whereas sucrose contents were higher in both cultivars grafted on Mazzard. However, the enzyme activities of both cultivars were higher on Mazzard rootstock than on Gisela 5. In conclusion, cold hardiness of sweet cherry graft combinations was suggested by increasing their TSS, reducing sugars, and sucrose contents significantly in the CA stage. Moreover, acid invertase and SS are down regulated during cold acclimation. Indeed the results suggested that Mazzard is more cold-hardy rootstock than Gisela 5.

Changes of Growth, Amino Acids, and Ionic Composition in Strawberry Plants under Salt Stress Conditions

Seedlings of two strawberry cultivars ‘Camarosa’ and ‘Chandler’ were grown using perlite in a greenhouse for 20 days, and then plants were watered with nutrient solution containing 0, 8.5, 17.0, and 34.0 mM sodium chloride (NaCl) for 6 months. Sodium chloride treatments generally reduced the leaf and root dry weight. Relative water content (RWC) of leaves was maintained despite the increased salt concentrations while loss of turgidity was increased by sodium chloride (NaCl) treatments in both cultivars. As the most variable amino acids, aspartic acid, glutamic acid, arginine, proline, serine, and alanine were determined under salt stress in plants. Sodium chloride treatments generally increased sodium (Na) and chloride (Cl) contents in all plant parts. The plants were able to maintain high potassium (K) levels in the aerial parts with the 8.5 mM NaCl treatment. It can be concluded that ‘Camarosa’ has the ability to osmotic regulation. ‘Chandler’ also tolerates the salt injury at low salt concentrations.

Seasonal alteration of sugar metabolism in strawberry (Fragaria × ananassa) plants during cold-acclimated and non-acclimated stages

Plants of strawberry cvs Aromas and Diamante were removed from the field in cold acclimated (CA, January) and non-acclimated (NA, July) stages. Crown parts of the plant were used for analysis. Apoplastic total soluble sugar (TSS), reducing sugars and sucrose contents did not change in both cultivars in both sampling stages. Symplastic TSS, reducing sugars and sucrose contents were higher in CA stage than that in NA stage in all samples. Considering the cultivars, TSS, reducing sugars and sucrose contents were higher in Diamante than Aromas. The activity of acid invertase (EC 3.2.1.26) enzyme was higher in NA stage than that in CA stage in the apoplast of crown tissues. In general, acid invertase activity in the symplast of crown tissues in both cultivars was higher in CA stage compared with that in NA stage although not significantly, as a function of hardening. In addition generally, the cultivars had significantly higher sucrose synthase (SS) (EC 2.4.2.13) activity in the symplast of crown tissues when sampled at the CA than at the NA stage. In conclusion, cold-hardiness of strawberry was suggested by increasing their TSS, reducing sugars and sucrose contents significantly in the symplast of crown tissues in the CA stage. Moreover, both acid invertase and SS are regulated by coldacclimation and deacclimation.

Determination of Salt Tolerance of ‘Camarosa’ and ‘Chandler’ Strawberries Grown in Perlite and Perlite: Zeolite Media

ABSTRACT The effects of salt (NaCl) applications of various concentrations (0, 500, 1000 and 2000 mg/L) for 6 months on ‘Camarosa’ and ‘Chandler’ strawberry varieties grown in perlite and perlite:zeolite (1:1) media were investigated. In order to determine the salt resistance of varieties, the tolerance index (T.I.) and tolerance ratio (T.R.) were calculated on the basis of total chlorophyll content, and leaf and root dry weight. Also, the ability of keep in balance for potassium:sodium (K:Na) ratio in the aerial part and roots of plants were considered. It was determined that the highest T.I. and T.R. values calculated on the basis of leaf and root dry weight in cv. Camarosa in both media. Concerning the evaluations calculated on the basis of total chlorophyll, the results indicated that ‘Chandler’ is more resistant in perlite medium, ‘Camarosa’ is more resistant in perlite:zeolite (1:1) medium. K:Na ratio decreased with increasing salinity in both varieties. However, it was determined that K:Na ratio is higher in cv. Chandler, i.e., 0.83 than in cv. Camarosa (0.61). As a conclusion, it was determined that ‘Camarosa’ was more resistant to salt than ‘Chandler’. In addition, regarding the salt resistant performance of plants, perlite:zeolite (1:1) medium had more effective results than perlite.