Azam Amiri; Bahram Baninasab
Abstract
Introduction: Salinity is a common abiotic stress that seriously affects crop production in some parts of the world, particularly in arid and semi-arid regions. The deleterious effects of salinity on plant growth are associated with low osmotic potential of soil solution (water stress), nutritional imbalance, ...
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Introduction: Salinity is a common abiotic stress that seriously affects crop production in some parts of the world, particularly in arid and semi-arid regions. The deleterious effects of salinity on plant growth are associated with low osmotic potential of soil solution (water stress), nutritional imbalance, specific ion effect (salt stress), or a combination of these factors. Paclobutrazol (PBZ), a member of the triazole plant growth inhibitor group, is a broad-spectrum gibberellin biosynthesis inhibitor. Triazoles have both fungal toxicity and plant growth regulatory effects. They also increase tolerance of various plant species to biotic and abiotic stresses, including fungal pathogens, drought, air pollutants, and low- and high-temperature stress. According to our knowledge, there are no reports on the effects of exogenous PBZ enhancing vegetative peach- almond hybrid (GF 677) rootstock tolerance to salt stress. Therefore, the objective of this work was the possibility test of this idea that PBZ application would protect GF 677 rootstock from damaging effects of salinity.
Materials and Methods: One-year-old rooted cuttings of GF 677 were grown in in plastic pots in the research greenhouse of Agricultural College, Isfahan University of Technology of Iran. The minimum and maximum temperatures during the experiment period were 19 and 32˚C, respectively. After cutting establishment (3 months), the plants were sprayed twice (with a 7 days interval) with 0 (control), 20 and 40 mg l-1 PBZ to the point of run-off. One week after the second foliar application of PBZ, each plants was subjected to one of several salt stress treatments. The salt treatments (0, 25 and 50 mM NaCl) were applied to the pots intervals in 0.5 l of irrigation water. To avoid osmotic shock, the NaCl concentration was increased gradually. The layout was a 3×3 factorial experiment in a completely randomized design, with four replications. The experimental measurements were carried out 60 days after beginning the salt treatments.
Results and Discussion: The results showed that salt stress and application of PBZ significantly affected injury rating valve (IRV). The Injury rating value of plants was found to increase significantly as the salt concentration was raised. After exposure to salt stress those plants that did not receive PBZ exhibited higher symptoms of salt injury. There was a significant interaction between salinity and PBZ application. The lowest IRV in all NaCl concentrations observed when 20 mg l-1 PBZ was applied. Salinity caused significant decrease leaf parameters so that the lowest means of leaf number (12.5) and leaf fresh weight (6.52 g) were recorded at 50 mM NaCl treatment, showing a 55.80% and 41.78% decrease compared with the control, respectively. The application of PBZ significantly increased leaf number, with the largest increase when 40 mg l-1 PBZ was applied. The interaction between salinity and the application of PBZ showed that at 25 mM NaCl maximum valve of leaf number was observed in plants after spraying with 40 mg l-1 PBZ. Relative leaf chlorophyll (RLC) was not affected by salt stress. Application of PBZ significantly increased relative RLC value compared with the control, with the largest increase in RLC measured when 20 mg l-1 PBZ was applied. The interaction between salinity and the application of PBZ showed that at 50 mM NaCl maximum valve of RLC was observed in plants after spraying with 20 mg l-1 PBZ. The proline content of leaves was significantly influenced by the salt stress and PBZ application, but not their interaction. Salinity stress, increased proline content in the leaves of salt-treated plants. At 50 mM NaCl, proline content was maximum compared to those of the controls and other salt levels. PBZ treatment increased proline content in leaves. The highest proline content was obtained from leaves of the plants treated with 40 mg l-1 PBZ (55.62μmol g-1 FW), which was 39.18 % more than the control. Salt stress significantly reduced the relative water content (RWC) with maximum reduction observed in plants grown by 50 mM NaCl. Application of PBZ significantly increased RWC compared with the control, with the largest increasing in RWC at 20 mg l-1 PBZ application. Leaf electrolyte leakage was affected by both salt stress and PBZ application. Salt stress significantly increased leaf electrolyte leakage, with a maximum increase observed in plants grown by 50 mM NaCl. The application of PBZ significantly decreased electrolyte leakage in leaf discs, with the largest decreaseing in leaf electrolyte leakage measured at 20 mg l-1 PBZ application..There was a significant interaction between salinity × PBZ concentrations. However, the greatest decreasing in leaf electrolyte leakage occurred at 40 mg l-1 PBZ in non-saline condition. In this study, the correlation between vegetation and physiological parameters of GF677 plants subjected to salt stress was analyzed. These correlations suggested that salt injury symptoms was negatively correlated with number and fresh weight of a leaf, RWC, RLC, but positively correlated with proline content and leaf electrolyte leakage.
Conclusions: in overall, this investigation revealed that salt stress had an inhibitory effect on the vegetative growth of GF 677 plants. The responses of GF 677 plants to the PBZ treatments suggest that the application of PBZ could partially increase the survival capacity of GF 677 plants and protect the plants against injuries such salt stress.
Mehri Mashayekhi; Mohammad Esmaeil Amiri; Fariborz Habibi
Abstract
Introduction: Salinity is the most significant abiotic factor limiting crop productivity and several physiological responses, including modification of ion balance, water status, mineral nutrition, stomatal behavior, photosynthetic efficiency and so on. The GF677 (Prunuspersica×Prunusamygdalus) is widelyusedas ...
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Introduction: Salinity is the most significant abiotic factor limiting crop productivity and several physiological responses, including modification of ion balance, water status, mineral nutrition, stomatal behavior, photosynthetic efficiency and so on. The GF677 (Prunuspersica×Prunusamygdalus) is widelyusedas rootstock for peach and almond. It is mainly used as a rootstock because of its resistance to drought, calcic soil and Fe deficiency. Nowadays, using tissue culture techniques is very popular for the selection of plant resistant to abiotic stress (in vitro salinity); because in vitro conditions are more controllable than in vivo conditions and the large number of genotypes can be evaluated in a limited space. For example, in the field, plants are exposed to variable biological and climatic conditions which result in some interaction effects. In other words, the nutrition and climatic effects are easily controllable in the in vitro conditions all over the year. The objective of this study is to identify biochemical markers of salinity stress of GF677 rootstock under in vitro conditions.
Materials and Methods: Plantlets of GF677 rootstock were subcultured into the Murashige and Skoog (MS) proliferation medium containing1 mg/l BA (6-Benzyladenine)and 0.1 mg/l NAA (naphthaline acetic acid) with different concentrations (0, 40, 80 and 120 mM) of sodium chloride (NaCl) with four replicates. Cultures were transferred to the growth chamber with temperature of 25±2°C, relative humidity of 70%, under a 16/8 h (day/night) photoperiod. Data were collected at the end of the experiment (6th weeks). Antioxidant enzymes activity (catalase and peroxidase),total protein content, proline content, soluble sugars, and Na and Cl were measured. The experiments were set up in a completely randomized design (CRD) with four replicates (a vessel in each replicate) and statistical analysis was performed using MSTAT-C program. Means were separated according to the Duncan’s multiple range test (DNMRT) at 0.05 level of probability.
Results and Discussion: After six weeks, the results showed that by increasing salinity levelsin the culture medium, antioxidant enzymes activity (catalase and peroxidase),total protein content, proline content and soluble sugars increased significantly. The antioxidant enzyme activities (catalase and peroxidase) were increased significantly in the GF677 rootstock by increasing salinity levels. Catalase activity increased with increasing salinity levels, such that the maximum value (0.61 [abs/min /mg protein (f.m)]) was observed in 80 mM sodium chloride treatment. The lowest catalase activity (0.11 mg [abs/min /mg protein (f.m)]) was observed in 120 mM. The highest of peroxidase enzyme activity (0.109 and 0.105 [abs/min /mg protein (f.m)]), was obtained in 80 and 40 mM, respectively. Also, by increasing the salinity level, total protein content increased significantly in GF677 plantlets. The highest total protein was observed in 80 mM sodium chloride. By increasing salinity levels, proline content increased compared to the control at the GF677 rootstock, but no significant difference was observed between salinity levels. The highest accumulation of proline was obtained in 80 and 120 mM, respectively, while the lowest proline was obtained in control. By increasing salinity levels, soluble sugars increased in GF677 rootstock. The highest accumulation of soluble sugars was obtained in 80 mM. By increasing salinity levels in the cultural medium, the uptakeof sodium (Na+) and chlorine (Cl-) significantly increased in GF677 rootstocks over the six-week culture period. The highest uptake of Na and Cl ions in plant tissue was observed in 4th week. The results showed that with increasing salinity levels (80 to 120 mM), leaf chlorophyll index (SPAD unit) decreased in GF677 rootstock. The lowest chlorophyll index was observed in 120 mM treatment, while the highest leaf chlorophyll index was obtained in the control treatment.
Conclusion: According to the results and analysis of biochemical and enzymatic responses,it can be concluded that GF677 is a concentration tolerant to salinity up to 120 mM. The highest amount of biochemical responses and enzymatic activity was observed at 80 mM, where the continued growth of the plant was in terms of salinity. The rootstock was due to antioxidant defense mechanisms such as antioxidant systems, osmotic adjustment by proline and soluble sugars and increasing protein synthesis can sustain growth even under salinity conditions, as a tolerant rootstock was used for peach and almond cultivars.
Fariborz Habibi; Mohammad Esmaeil Amiri
Abstract
In this experiment, physiological responses of two citrus rootstocks [sour orange (Citrus aurantium L.) and trifoliate orange (Poncirus trifoliata Raf.)] were investigated under in vitro salt stress conditions. This study was conducted on a completely randomized factorial design. Explants (Nucellar seedling ...
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In this experiment, physiological responses of two citrus rootstocks [sour orange (Citrus aurantium L.) and trifoliate orange (Poncirus trifoliata Raf.)] were investigated under in vitro salt stress conditions. This study was conducted on a completely randomized factorial design. Explants (Nucellar seedling obtained from seeds) of both rootstocks were transferred to Murashige and Skoog (MS) solid proliferation medium containing 8.9 µM BA and 0.5 µM NAA with different concentrations 0, 50, 100, 150, 200 mM of sodium chloride (NaCl) whit six replicates. Results show that leaf chlorophyll index, photosynthesis rate, stomatal conductance, internal CO2 concentration (Ci), total protein content decreased in both rootstocks by increasing salinity levels, although there was no significant difference for above-mentioned characteristics in the interaction of salinity and rootstock. The amounts of reduction in total protein content, chlorophyll loss and internal CO2 concentration (Ci), in trifoliate orange genotype were greater than the sour orange. Also, peroxidase enzyme activity increased by increasing salinity level in both rootstocks, but, the rate of increase in the trifoliate orange was higher than the sour orange. By increasing salinity levels in the cultural medium, the uptake of sodium (Na+) and chlorine (Cl-) significantly increased in both rootstocks over 6 weeks culture period. Comparison in to trifoliate orange, sour orange less sodium and chlorine were taken up. Based obtained results, can be declared, salt tolerance has a negative correlation with Na+ and Cl- content in plant tissues, and the plant have a less Na+ and Cl- in tissues are more resistant. Thus, sour orange was more tolerant than trifoliate orange to salt stress and could be has more resistant to high concentration salinity.
