Salinity is a major environmental stress which adversely affects germination and seedling establishment in a wide variety of crops. However, studying of seeds with different plant growth regulators may helpful to alleviate the deleterious effects of salinity and enhance germination and seedling growth in salt stress environment. In present experiment we investigated the effects of 5-Aminolevolinic Acid (ALA) on germination and seedling growth parameters of milk thistle grown at different salinity levels. The experiment was arranged in factorial experiment in randomized complete block design with three replications. Results revealed that all parameters were significantly affected by salinity conditions and concentrations of ALA. In general, all parameters decreased with increasing NaCl concentrations, however the amount of these parameters increased with increasing ALA concentration. In addition, different between 0.25 and 0.50mM was not significant for germination percentage, shoot length, seedling fresh weight, seedling dry weight and leaf length. Interaction effects showed that highest value of root length and leaf length were produced from the 0.25 and 0.50mM ALA under the control treatment of salinity level. In contrast, the highest amount of seedling fresh weight were obtained from 0.25 and 0.50mM concentrations of ALA under control treatment of salinity. In general, our results suggest that ALA at low concentrations (0.25-1mM) has the potential to improve salt tolerance in milk thistle seedlings through concentrations treatment. We hope ALA may be useful in helping to solve serious problems occurring on a global scale, such as the desertification of green lands and salt damage to farm lands.
Drought stress is a major constraint for crop production in arid and semiarid regions, such as Iran. In thisstudy, the possibility of enhancing drought stress tolerance of sweet basil plant (Ocimum basilicum L.) byexogenous application of Salicylic acid (SA) was investigated. The layout was factorial experiment inrandomized complete block design (RCBD) with 3 levels of drought stress including stress-freeconditions, mild stress and severe stress and 3 concentrations of SA (including 0, 0.75 and 1.5 mM) asmain factors and 3 replicate. The statistical analysis showed that drought stress and application of SA hadsignificant effects on the morphological, physiological and biochemical parameters of the plant such asplant height, fresh and dry weight, relative water content (RWC), chlorophyll (Chl), proline andelectrolyte leakage (EL). Result showed that drought stress imposed negative effects on plant growth andproductivity. In drought conditions, growth parameters, Chl content, RWC reduced, but proline contentand EL increased. SA application significantly caused increasing of plant growth characters, photosyntheticpigments, RWC and proline and decreased EL. In this experiment, SA application withincreasing growth rate and changing plant physiological process decreased adverse effects of droughtstress on sweet basil plants.
Salinization and alkalization of soils are agricultural problems in arid and semiarid regions of the world such as Iran. In this experiment the effects of salicylic acid (SA) on resistance of pepper plants under salt stress (SS) and alkali stress (AS) were evaluated. Treatments include 0 and 150 mM of SS, 0, 50 and 100 mM of AS and 0, 0.75 and 1.5 mM SA. Results showed that SS and AS imposed negative effects on pepper plant growth and productivity. Reduction in growth and yield in SS was higher than AS and maximum reduction occurred in high mixed stresses. SA application improved growth parameters and increased yield, relative water content (RWC) and chlorophyll of plants subjected to SS and AS and provided significant protection against stress compared to non-SA-treated plants. For most traits, 0.75 mM of SA was more effective than 1.5 mM concentration. SA ameliorated the injury caused by SS and AS by increasing chlorophyll and RWC and inhibiting proline accumulation and leaf electrolyte leakage (EL). In general, results indicate that salinity and alkalinity have negative effects on growth and yield of pepper plants and these negative effects can be ameliorated by application of SA.
A field experiment was conducted to study the effect of different methods of urea application on yield, yield components and maize grain composition. The investigated factors were urea fertilization methods (foliar application and soil application as side dress) and four maize hybrids including NS 620, Konsur 580, Jeta 670 and control SC 704 arranged in a split plot based on complete block design with four replications. The results showed that soil urea application increased grain yield compared to foliar application, but protein percentage was higher when foliar application was used. The highest grain yield was achieved for NS 620 that was due to higher number of grain rows per ear, number of grains per ear row and plant height. Konsur 580 showed that the greatest protein percentage with foliar urea application. This study showed that urea application method can affect both the quality and quantity of grain maize.
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