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  • Inhibition and recovery of germination and growing ability of seedlings under and after osmotic stress induced by polyethylene glycol in 8 pea genotypes
    53-59.
    Views:
    123

    Germination and early seedling growth of eight pea genotypes were examined under and soon after different (5%, 10%, 15%, and 20%) PEG treatments. Seeds were germinated on PEG solution for 3 or 6 days and then further germinated and cultured on filter paper moistened by water for 3 and 6 days. The length and fresh weight of shoots and roots of seedlings were measured and used for evaluation of genotypes. Roots were less inhibited by osmotic stress than shoots similarly to other plant species. The variability among the genotypes was the greatest in the case of shoot growth at 5% PEG treatment and in the case of root growth at 15% PEG treatment. Results suggest that growing responses of genotypes after cessation of stress are more suitable for the evaluation of their osmotic tolerance, than their responses expressed during in vitro stress conditions. Genotypes with relatively high or low osmotic stress tolerance, respectively, could be distinguished with 6 days after recovery from 3-day-long 15% PEG treatment concerning the rate of shoot weight to root weight.

  • Grape variety comparison of different stress tolerance based on the quantitative measurement of carbohydrates
    37-40.
    Views:
    156

    The analyses of various host-pathogen relationships have established the response reaction roles of carbohydrates — especially monosaccharides — measurable in the vegetal parts of the host. Published results also provide information concerning the way various pathogens utilize carbohydrates and concerning the carbohydrates pathogens prefer out of the "selection" provided by the host plant. The role of carbohydrates in the response reactions to abiotic stress has been studied on several plant species as well — currently, too, it is an often discussed area of research. The above-mentioned results form the basis of our intention to study the connection between susceptibility to grey mould and the quantity of measurable carbohydrates in the leaves of grape varieties of various stress tolerance levels.

  • Ecological drought resistance and adaptability of apple varieties
    113-122.
    Views:
    296

    For adequate yields in apple plantations, during the long growing period of the fruit primordia, one of the decisive factors is water supply. Indicators of stress are valuable signs for the diagnosis of drought and necessity of watering, i.e. planning the irrigation of plantations. The aim of the present study was to find reliable signs of water stress on apple trees and at the same time conclude on the drought tolerance of different varieties. The plantation of apple varieties grafted on various stocks and cultivated according to different systems (irrigated, non irrigated, integrate and biological) has been examined continuously by leaf analysis. Along the period of growing fruits, measurements were made in the field, then the leaf samples were analysed in the laboratory for composition of pigments, carbohydrates and antioxidants, as well as the histology of the tissues checked. Without irrigation, the mean leaf mass and the relative chlorophyll content (SPAD) of the variety Idared on M4 stocks increases beyond the values of 50 SPAD, whereas on M26 stock and integrated system, it declines. In the collection of varieties, grown according to the „integrated” system, during the development of fruits, ‘Gála’ and ‘Remo’ varieties have been affiliated to the “less susceptible” group regarding drought tolerance because of the leaf morphology, structure and content of SPAD and antioxidants. However, ‘Idared’ and ‘Jonagold’ belong to the “susceptible” group. To the same group are ranged the ‘Akane, Red Rome vanWell, Pink Lady’ varieties. Those varieties reacted to a short period of drought by increased production (content) of carbohydrates. Regarding changes of carbohydrate content ‘Greensleeves’ and ‘Ozark Gold’ varieties belong to the moderately water dependent (requiring) group. In the field, SPAD-tests facilitated the measurement of nutrient-uptake and incorporation, which is proved by the tight correlation between the data of SPAD and the increment of leaf weight (r=0.76–r=0.88), however, this depends on the variety too. SPAD is an indicator of water supply and is related with the density of stomata, cannot used for the selection of water-exigent varieties but for (drought) tolerant ones. In integrated culture, the (drought) susceptible varieties display (water-soluble) hydrophilic and lipophilic antioxidants (ACWand ACL resp.) the quantity of which may have some role in drought tolerance.

  • The selection and cultivation of Tilia clones tolerating polluted urban environment
    82-86.
    Views:
    207

    Two urban stress tolerant Tilia clones were selected by the Department of Floriculture and Dendrology. The mother trees of the Observed clones were found in an alley of linden trees, settled on a traffic island of a busy two-lane road.

    Tilia hybrid 'Saint Stephen' has a beautiful cone-shaped crown, the leaves are bright green and they keep their green colour for much longer time than the leaves on the other trees in the alley. In the nursery the Tilia hybrid 'Saint Stephen' was budded on T. cordata, T. platyphyllos and T. argentea and it had good compatibility with every rootstock. The average height of the one year old buddings was 200 cm and the buddings kept their good growing capacity in the following years as well. They had an outstanding growing capability comparing with the other Tilia cultivars.

    Tilia platyphyllos 'K3' clone has similar cone-shaped crown. The growing vigor and urban stress tolerance seems to be better than Tilia hybrid 'Saint Stephen'.

     

  • Boistimulator effect of stress tolerant rhizobacteria on horticultural models
    83-87.
    Views:
    186

    The tolerant bacteria for abiotic stresses such salinity, drought, and different pH have been used as a good tool to improve plant growth in sustainable agriculture. A pot experiment was conducted to evaluate the potential of isolated stresstolerant bacteria for red mud-polluted soil on growth performance of giant reed plants with increasing concentrations of NaCl 0.0; 0.1; 0.2; 0.3; 0.5; 1.0% under gnotobiotic conditions. At the same time biostimulator potential of isolated bacteria was observed in case of radish in vitro germination experiment under salt stress. It was found that the observed bacterial strain can tolerate the salt and pH moderately however it is resistant against hydrogen-peroxide caused oxidative stress in high concentration (up to 2640 mM). Molecular identification, basis on 16S rDNA showed 98% similarity to the Bacillus aryabhattai bacterial strain. The isolated strain alleviated the negative effect of salt (0.05%) for the radish seed germination. However in higher salt concentration (≥0.1%) the bacterial mitigating effect vanished. The inhibition of increasing salt concentration for giant reed plantlets was also alleviated by halotolerant bacteria treatment (≥0.5%).

  • Frost induced changes in enzyme activities and carbohydrate content in the spurs of some pear cultivars during the dormancy
    41-44.
    Views:
    194

    Frost tolerance of pear cultivars was checked after artificial cold treatment in 2003-2005. Limbs collected during the endodormancy were exposed in a climatic chamber for 24 hours to —25; —28 °C, while those collected in the ecodormancy were kept at —15 and —18 °C. Frost damages of buds were registered according to a visually defined scale, then peroxidase (POD), polyphenol oxidase (PPO) enzyme activities and carbohydrate contents were checked in buds and spur-part below the buds. POD activity of untreated control in tissue below buds was higher than in the buds, which were increasing continuously during the endodormancy and decreased at the end of the ecodormancy. During endodormancy, cold treatment of —25 and —28 °C effected different changes of enzyme activity in buds of the cultivars. In the ecodormancy, enzyme activities increased after a cold treatment of —15 °C, whereas the activities decreased significantly after —18 °C. `Kaiser' — susceptible to frost — with its higher values of both enzyme activities marked out from other cultivars, which is correlated with its stress response. Changes in carbohydrate components — especially in glucose — of buds monitored well the different stress responses of tolerant and resistant pear cultivars induced by frost stress.

  • Comparative study of three rosemary (Rosmarinus officinalis L.) clones during the growing season
    67-72.
    Views:
    153

    The growth rate of three rosemary clones, `Harmat', 'Salem' and `Horvát', their essential oil content and its components as well as the total phenol content and total antioxidant capacity in their aqueous and ethanolic extracts were compaired. Total phenol content (determined by Folin-Ciocalteau reagent) and antioxidant power (FRAP-value) of aqueous and ethanolic rosemary extracts were measured by spectrophotometric method. The essential oil content was determined from drug by water-steam distillation. `Harmat' showed the most intensive growth through the vegetation period. The total antioxidant power of the ethanolic extracts from all the three clones was similar: a decrease was observed at the end of the season. In most cases more antioxidant compounds were dissolved in the aqueous extracts. The total quantity of phenolic compounds shows a good correlation with the potential extent of stress effects. The difference among the phenol contents of the various clones can be derived from the difference in their tolerance, because phenols have antioxidant effects contributing to protection against harmful impacts. Difference between the two extraction methods (aqueous and ethanolic) is due to the distinct solubility of compounds. Some other components, like essential oil compounds also possess antioxidant effect and in this way they may influence the antioxidant power of extracts.

  • Effects of silicon in plants with particular reference to horticultural crops - Review article
    95-105.
    Views:
    295

    Silicon (Si) has long been considered as non-essential element for plant’s growth and production. Numerous efforts are being made for the discovery of its beneficial effects with large scale studies laying foundation for new findings and hypotheses. Therefore, Si has been suggested to be a quasi-essential element due to its positive effects against biotic and abiotic stresses alike. Though Si is the second most abundant element in the soil profile, its availability to plants is limited to the form of monosilicic acid only. Besides, plants’ ability to take-up Si and use it in their physiological processes also depends on the available transporters associated with it. Thus, the present review covers uptake and transport of silicon in plants as well as Si mediated physiological processes, including mechanisms underlying induced tolerance against biotic and abiotic stresses with a particular emphasis on horticultural species.

  • Luminescence variations in cucumber (Cucumis sativus L.) leaves derived from different regeneration systems
    50-52.
    Views:
    154

    Plants obtained from in vitro culture can show increased susceptibility to environmental stress conditions. In the process of their adaptation to natural conditions it requires monitoring of their physiological state. The methods used to check this phenomenon should estimate quickly and exactly the tolerance to suboptimal environmental factors. Such requirements are satisfied by the methods of measuring chlorophyll luminescence in vivo, e.g. fluorescence induction and delayed luminescence. The objects of our studies were cucumber plants regenerated from cultures of callus and embryogenic cell suspension, as well as the plants obtained from seeds. The plants derived from in vitro cultures displayed a poor physiological condition at the early phase of adaptation characterised by higher susceptibility both to stress caused by increased density of the light flux and low temperature (4 °C) in comparison with the plants obtained from seeds.

     

  • Effects of different levels of NaCl and CaCl2 on seed germination characteristics of Melissa officinalis L. and Ocimum basilicum L.
    21-25.
    Views:
    274

    More than 15 million hectares of Iran’s land areas are suffering from salinity.We investigated the effects of two types of salt (NaCl, CaCl2) in different levels on the germination and initial growth of two medicinal and aromatic plants, Melissa officinalis L. and Ocimum basilicum L. The experiment was carried out in Qazvin Agriculture and Natural Resource Research Center based on a randomized complete block design, for 14 days in a germinator. Sweet basil germinated above 50% in each saline treatment (EC=10 dSm-1), in alkali treatment (CaCl2=18800 mg/L) and in sodic-saline treatment (Ec=10 dSm-1; SAR=5.6), however at the highest concentrations germination was slowed down. Lemon balm showed a higher sensitivity: except the lowest NaCl treatment, each other ones inhibited germination and its rate to some extent. The combined treatments of both salts increased the stress reactions. However, seedling growth was less effected. The results showed a stimulating effect of NaCl treatment in 2500 mg/L (EC<5 dSm-1) for both species concerning germination and seedling growth.