نشریه روابط خاک و گیاه
پیاپی 33 (بهار 1397)

Silicon (Si) is a beneficial element for on plant growth and development that plays an important role in plant resistance to environmental stresses such as salinity and drought. The present research was conducted to study the effect of Si and water deficit on biochemical, physio-morphological and qualitative traits of cut rose cv. Club-Nika under greenhouse conditions. The factorial experiment had three levels of Si (0, 0.5 and 1 mM) and three levels of water deficit (100 (control), 75 and 50% of the irrigation needs), combined in a completely randomized blocks design with four replications. In the current research, qualitative attributes such as number of extra-quality stems, shoot diameter, flower diameter and biochemical traits such as chlorophyll and proline content of leaves were measured. Results showed that plants grown in the 100% water-requirement treatment had higher shoot diameter, number of extra-quality stems, fresh and dry weights of flowering shoot, flower diameter, leaf area and relative water content than the plants exposed to water stress conditions. Bud sprouting in the100% water requirement treatment happened faster (about 6.83 days) than the plants under stress conditions. However, water stress treatments (50 and 75 percent) did not affect total number of stems, chlorophyll content and proline content of the leaves. In this research, although addition of 1 mM Si was capable of enhancing most qualitative traits of cut roses, however, this difference was not statistically significant. It seems that lack of effect of silicon treatments might be related to characteristics of silicon distribution in the leaves and also ineffectiveness of these treatments on cuticular transpiration and stomatal conduction. Generally, the results showed that cut roses adapted themselves through changes in morphological characteristics and not any other mechanisms like osmoregulation such as proline synthesis.

Optimum nutrition is one the most effective strategies in floriculture industry. In this regard, a factorial experiment designed based on CRD with three replications on New Guinea impatiens in greenhouse. Treatments were slow release fertilizer (12-11-18-2.7MgO-8S) at 5 levels (0, 1.5, 3, 4.5 and 6 kg/m3) and humic acid at three levels (0, 2 and 4 kg/m3), mixed with substrate. The F1 seeds of New Guinea impatiens planted in plug trays consisting of 50% peat moss, 40% perlite and 10% rice husk (v/v) as medium. After 70 days, traits such as transplant height, number of leaves, shoot diameter, total fresh and dry weight of shoots and roots, chlorophyll content and leaf nutrient concentration was evaluated. Results showed that the highest transplant height (4.38 cm) was observed in applying 3 kg/m3 of slow-release fertilizer mixed with 4 kg/m3 of humic acid, the greatest stem diameter (3 mm) was observed in 4.5 kg/m3 of slow-release fertilizer treatment and the highest number of leaves (18.9) was observed in 3 kg/m3 of slow-release fertilizer treatment. It seems that slow-release fertilizer increased nutrient elements efficiency and decreased their leaching from the substrate and also, humic acid increased plant nutrient uptake during transplant production. According to the results of this research, it could be recommended to use 3-4.5 kg/m3 of slow- release fertilizer and 2-4 kg/m3 of humic acid in the substrate for transplant production of New Guinea impatiens.

In order to identify drought tolerant strawberry (Fragaria ananassa Duch.) cultivars and investigate some of their morphological, quantitative and qualitative characteristics, a research was conducted as split plots based on randomized complete blocks design with three replications under greenhouse conditions. Deficit irrigation stress was considered as the main plot factor at 4 levels (control (0), 20, 40 and 60 percent) and subplot factor was cultivar at 6 levels (Kurdistan, Camarosa, Merak, Paros, Queen Eliza and Selva). Leaf area showed a 41.42% reduction, and number of flowers and fruits showed 90% reduction in 60% stress treatment in comparison to the control. Total soluble solids (TSS) showed an increasing trend up to 40% stress severity. As stress increased, titrable acidity (TA) showed a decreasing trend. A high heritability was observed for number of flowers and fruits, fruit weight and TSS. Considering the three-dimensional plot of STI, and , the Kurdistan and Camarosa cultivars were identified as the most suitable cultivars in both deficit irrigation stress and non-stress conditions. So, these cultivars could be used in breeding programs in order to increase drought tolerance. According to the responses of cultivars to deficit-water stress, more leaf area, number of flowers, number of fruits number, fruit weight, and TSS, and lower TA are introduced as the selection criteria for drought tolerant strawberry cultivars.

Nowadays, spraying and foliar feeding represent one of the most effective techniques of applying essential nutrient elements to crops and to optimize the application of fertilizers in agriculture. In this research, effect of foliar application of different concentrations of ammonium sulfate on quantity and quality traits of cucumber under greenhouse conditions was investigated. The research was performed under completely randomized design with 6 treatments of foliar application of ammonium sulfate (0, 25, 50, 75, 100 and 150 mM) with 4 replications. Results of this research showed that plants in 25 mM ammonium sulfate and control treatments had the highest chlorophyll content, number of lateral shoots, number of fruits, and fruit yield. Vegetative traits such as chlorophyll index, number of lateral shoots, number of fruits, and fruit yield were reduced significantly under 100 and 150 mM foliar application of ammonium sulfate. The lowest number of fruits and yield were obtained in 150 mM treatment. Plants in 100 mM treatment had the highest percent of leaf dry weight. Foliar application of ammonium sulfate, except 25 mM, resulted in fruit firmness reduction as compared to control plants. On the other hand, foliar application of ammonium sulfate, regardless of concentration, resulted in higher fruit weight loss compared to fruits from control plants under normal room temperature. Therefore, for optimum growth and production of cucumber under greenhouse conditions, foliar application of 25 mM ammonium sulfate (low concentration) is recommended.

To evaluate the effect of dipping time of bulb in complete NPK fertilizer on quantitative and qualitative traits of tuberose (Polianthes tuberosa L. cv. Double), a factorial experiment based on completely randomized design with four replications was conducted under the greenhouse conditions. The first factor was three bulb-dipping times (20, 40 and 60 min) and the second factor was four concentrations of complete NPK fertilizer (0, 3, 6 and 9 g/L). The studied traits were plant height, length of inflorescence, length and diameter of first floret, number of florets, leaf length and width, number of leaves and flowering stem diameter. Results showed that the highest values of the length of flowering stem (72.06 cm), the first floret diameter (4.28 cm) and number of florets (29.14) were obtained from 60 minutes dipping. Also, highest values of the length of flowering stem (73.58 cm), inflorescence height (27.91 cm) and diameter of the first floret (4.34 cm) were obtained from 3 g/L of complete NPK fertilizer treatment. The interaction effects showed that maximum length of inflorescence (29.25 cm) and diameter of the first floret (5.02 cm) were obtained from 40 minutes dipping and application of 3 g/L NPK. Results of this study revealed that dipping of tuberose bulbs (before planting) in a solution of complete NPK fertilizer significantly improved the quantitative and qualitative traits of tuberose.

Selenium (Se) is an important microelement for plants and has been shown to improve growth under normal and stressed conditions. In this study, effect of Se and nano-selenium (N-Se) on hydroponically-grown tomato (Lycopersicum esculentum Mill. cv. ‘Halil’) on photosynthesis, antioxidant activity and total polyphenolic content was assessed. A factorial experiment with three temperature levels and Se and Nano Se level was designed. All plants were first exposed to Se or N-Se [Se at 0 µM (control), 2.5 µM (Se1), 5 µM (Se2) and 8 µM (Se3)], while N-Se was applied at four levels [1 µM (N-Se1), 4 µM (N-Se2), 8 µM (N-Se3) and 12 µM (N-Se4)]. Plants were exposed to three temperature levels [optimal temperature (25.17 ± 2 °C day/night = T1), high temperature (40 °C for 24 hr = T2) and low (chilling) temperature (10 °C for 24 hr = T3)]. They were then placed at normal temperature conditions for 7 days and photosynthetic and antioxidant factors were measured. Based on the results, both temperature-related stresses had negative effect on tomato growth. However, under high temperature stress, photosynthetic rate, mesophyll conductance and photosynthetic water use efficiency improved significantly. While, cold stress significantly enhanced transpiration. Most photosynthetic parameters could be improved in the presence of Se and N-Se. In Se1 treatment, under the temperature stress, the best photosynthetis rate, respiration and mesophyll conductance were obtained and plant resistance was enhanced. In N-Se treatments, N-Se1 had the best results of photosynthetis rate, antioxidant and phenol. However, in the absence of stress, the use of Se or N-Se, especially at higher concentrations (i.e., 5 and 8 µM), negatively impacted photosynthetic rate, internal CO2 of stomata, mesophyll conductance and photosynthetic water use efficiency. In general, under the low and high temperature stress, the physiological parameters of tomato were improved in N-Se1 treatment.

Salinity stress is one of the most important abiotic stresses which impares growth and productivity of plants worldwide. Foliar application of chemicals such as salicylic acid (SA) is among potential solutions to ameliorate damaging effects of salinity. The present research was carried out during 2015-2016 growing season in Research Greenhouse of University of Kurdistan to study the influence of salinity and salicylic acid on physiological attributes of tomato plants. Treatments included two levels of salinity (0 (control) and 50 mM NaCl) and three levels of salicylic acid (0, 1 and 2 mM) as foliar application. Based on the obtained results, most of the studied physiological traits were affected by salinity stress. In this regard, foliar application of SA increased leaf relative water content, membrane stability index, total chlorophyll content, proline and soluble carbohydrates in comparison to stressed tomato plants which were not treated with SA. Overall, our results suggest that foliar application of salicylic acid of tomato plants could be considered as a strategy to stimulate resistance to salinity stress and maintain tomato growth in terms of physiological attributes.