نشریه روابط خاک و گیاه
پیاپی 12 (زمستان 1391)

A greenhouse experiment was conducted to evaluate the effect of nitrogen (N) and salinity on dry matter yield, N uptake, nitrate (NO3-) concentration, agronomic efficiency (AE), physiologic efficiency (PE), apparent nitrogen recovery (ANR) and chlorophyll content of spinach shoots (cv. Viroflay), and also total N, NO3-N and electrical conductivity of post-harvest soil. The experiment was factorial, arranged as a completely randomized design with three replications. Treatments included five N rates (0, 75, 150, 225, and 300 mg/kg soil, as urea) and four salinity levels (0, 1, 2 and 3 g NaCl per kg soil). Results showed that application of 1 and 2 g NaCl had no significant effect on shoot yield of spinach. But application of 3 g NaCl significantly decreased shoot yield. Addition of salinity had no significant effect on plant NO3− concentration, leaf chlorophyll readings, AE and ANR of shoots, and total N of post-harvest soil; but reduced PE. Increasing N rate increased yield, total N uptake and chlorophyll readings of shoots, and total N of post-harvest soil: but reduced AE and PE. Application of high N level intensified the negative effects of 3 g NaCl salinity on reduction of spinach shoot's yield. Under the present experimental conditions, salinity tolerance level of Viroflay cultivar was higher than 8 dS/m, which is much more than the level reported in most references for spinach (2 dS/m). Application of 225 mg N (without salinity application) was the best N level for dry matter yield of spinach.

To investigate the effect of manganese (Mn) and salinity on some growth traits and chemical composition of pistachio (Pistacia vera L.) seedlings, a factorial experiment was carried out with two factors of salinity (0, 75, 150, 225 and 300 mM NaCl) and Mn (0, 12, 24 and 36 µM Mn from MnSO4 source) as completely randomized design with four replicates, in greenhouse in perlite medium. Results showed that salinity stress decreased leaf number, leaf area, dry weight of root and dry weight of shoots. Application of 300 mM NaCl, decreased leaf number, leaf area, dry weight of root and dry weight of shoots by 40, 30, 92 and 92 percent in comparison with control (zero level of salinity), respectively. But application of 12 and 24 µM Mn increased dry weight of shoots and leaf number by 29 and 24 percent in comparison with zero level of Mn, respectively. Since salinity reduced leaf area and dry weight of leaf, thus, because of dilution effect, the concentration of Mn, Zn and P was increased in shoots and roots and that of K was decreased. Application of Mn increased Mn, Zn, P and K concentration. Overall results of this research showed that salinity reduced vegetative growth, and since Mn has positive effects on some growth traits, it could probably increase the tolerance of pistachio to saline environments.

To study the effects of soil Cu and salinity levels on uptake of micronutrients by shoots and roots of pistachio seedlings, a factorial experiment was carried out as completely randomized design with three replications in greenhouse of College of Agriculture, Vali-e-Asr University of Rafsanjan, Iran, in May 2008. Treatments consisted of five salinity levels (0, 800, 1600, 2400 and 3200 mg NaCl per kg soil), four Cu levels (0, 2.5, 5 and 7.5 mg Cu per kg soil) and two pistachio cultivars (Badami Zarand and Ghazvini). Results showed that salinity stress significantly (P<0.05) decreased the uptake of micronutrients including Cu, Fe, Zn and Mn by shoots and roots. Application of 5 mg Cu per kg soil significantly increased the uptake of Cu, Fe and Mn by shoots, but had no significant effect on Zn uptake by shoots. Application of 2.5 mg Cu per kg soil significantly increased uptake of Cu, Fe and Mn by roots, while had no significant effect on Zn uptake by roots. In conclusion, the uptake of micronutrients in Badami Zarand cultivar was significantly higher than Ghazvini cultivar. Since trees suffer from deficiency of micronutrients in pistachio orchards, using Badami Zarand cultivar is recommended as pistachio rootstock.

Silicon has beneficial effects on growth, yield and improvement of the tolerance of some plants against biological and non-biological stresses. In order to study the effects of different concentrations of silicon (as Na2SiO3) on Iranian borage (Echium amoenum Fisch & C.A. mey), three levels of silicon (0, 0.2, 0.7 mM as Na2SiO3) and two levels of salinity (0 and 100 mM as NaCl) and two silicon-treatment durations (long time, 30 days, and short time, 15 days)) were considered. Borage plants were cultivated in hydroponics system in greenhouse and were treated with the abovementioned treatments. The experiment was carried out as completely randomized design with two factors of silicon and salinity and four replications. Some of the biochemical and physiological parameters related to salinity and silicon stress were investigated for short- and long – time periods. Based on the results, the proline content, reduced sugar, antocyanin, malondialdehyde, total chlorophyll and fresh and dry weights were changed significantly (P<0.05) in long-term silicon treatment and had some differences with short-time silicon treatment. In general, the results of this study indicated that proper concentration of silicon (0.2 mM), along with long-time silicon treatment, was effective on stress tolerance of Iranian borage plant.

Low photosynthetic rate is a major reason for yield reduction in drought-stress conditions. Therefore, a study was conducted in order to investigate the effect of drought stress on gas exchange, chlorophyll florescence, photosynthetic pigments, membrane stability, phenolic compounds and antioxidant capacity of leaves and their association with drought tolerance in 12 chickpea genotypes, which were stressed for two weeks. The split-plots experiment was conducted as a complete randomized blocks design with three replications. Drought stress (-3 and -6 bar) was the main plot and chickpea genotypes were the subplots, respectively. The results showed that with increasing drought stress, the photosynthetic rate, evapotranspiration, water use efficiency, chlorophyll a, chlorophyll b, total phenols and membrane stability index were significantly reduced. In contrast, drought stress did not impose any significant effect on quantum yield of photosystem II and radical scavenging activities of leaves. Genotypes varied widely in different studied traits. MCC753 genotype had the highest photosynthesis rate, evapotranspiration, chlorophyll b, and membrane stability index, MCC783 genotype had the highest water use efficiency, MCC759 genotype had the highest total phenols in leaves and MCC760 genotype had the highest radical scavenging activities. There was a positive significant correlation between photosynthesis and evapotranspiration with relative leaf water content and dry matter. In general, drought stress can reduce photosynthesis in chickpea genotypes, directly by reducing stomatal conductance and indirectly by oxidative stress and degradation of photosynthetic pigments and cell membrane. In this experiment, reduced stomatal conductance at more than five µm/m2 photosynthetic rate and reduced membrane stability and degradation of chlorophyll at less than this range led to effective reduction in photosynthetic rate.

Silicon (Si) nutrition may alleviate biotic and abiotic stresses including heavy metal deficiency and toxicity in plants. Iron deficiency and toxicity are important limiting factors in growth of rice. In the present study, role of Si nutrition on alleviation of iron deficiency and toxicity was investigated in rice plants. Plants were cultivated in greenhouse in hydroponics, using Yoshida solution, under different iron treatments (0, 2, 10, 20, 50, 100 and 250 mg/L as Fe- EDTA) and Si nutrition (0 and 1.5 mM as sodium silicate). Results revealed that both iron deficiency and toxicity imposed significant reduction in fresh and dry weight and length of plants. The activity of catalase was decreased in shoots due to iron deficiency. Activity of catalase in roots and cell wall peroxidase in shoots increased under iron toxicity compared with control plants. Si nutrition increased Si content in plants and improved plant growth in both iron deficiency (not in the absence of iron) and toxicity. Application of Si increased the activity of catalase in shoots and polyphenol oxidase in both roots and shoots under iron deficiency. Also, the activity of catalase in roots and polyphenol oxidase in shoots raised following iron toxicity. This in turn may reduce the oxidative stress in plants. In addition, increase of lignin in extreme iron toxicity due to Si nutrition may enhance sites of iron absorption in plant cell walls and decrease iron toxicity. The results indicated that Si nutrition could ameliorate harmful effects of iron deficiency and toxicity in rice plants possibly through improvement of antioxidant enzyme activity and reduction of oxidative stress.

Nickel (Ni) is necessary for plants at low concentrations; but excess Ni has toxic effects on plant growth. In this research, the effects of different Ni levels (0, 50, 100 and 200 µM from NiCl2) on leaf antioxidative response of two cucumber cultivars (Cucumis sativus L. cvs. Super Dominus and Negin) supplied with NH4NO3 as nitrogen source in nutrient solution was investigated. The results showed that by increasing Ni concentration in the nutrient solution and growth period, Ni concentration in the leaves of both cucumber cultivars was increased. This increase was greater at the vegetative growth stage compared with the reproductive stage. Higher levels of malonedialhdeyde (MDA) were also produced at the vegetative stage with respect to the reproductive stage. Application of 50 µM Ni significantly reduced MDA concentration, produced from lipid peroxidation, in comparison with the Ni-free control treatment. The effect of Ni on catalase (CAT) activity was dependent on the cucumber cultivar and concentration of this element in the growth medium. At the vegetative stage, Ni addition had no significant effect on activity of CAT in Super Dominus cultivar, while significantly reduced leaf activity of CAT in Negin cultivar. At the reproductive stage, Ni addition reduced activity of CAT in comparison with Ni-free treatment, regardless of the cucumber cultivar. Results showed that at the vegetative stage, application of 50 µM Ni to the growth medium resulted in lower activity of guaiacol peroxidase (GPX) in the leaves of both cucumber cultivars. By increasing the Ni level to 100 and 200 µM, the activity of this enzyme was increased. At the reproductive stage, activity of the ascorbate peroxidase (APX) in the leaves was dependent on the cultivar and concentration of this element in the medium. According to the results obtained from the present study, in general, the effect of Ni on activity of antioxidant enzymes in cucumber leaves varies with plant cultivar, Ni level and enzyme type.

In order to determine the most appropriate nutrient solution spraying interval and effects of light quality in the root zone on anthurium in aeroponic system, a split plot experiment, with completely randomized design, was carried out in a greenhouse located in the city of Karaj, Iran. In this study, time between the sprays was the main plot and consisted of two levels (2 minutes spray and 30 minutes without spray, and 2 minutes spray and 45 minutes without spray) and color of the containers was the sub plot at three levels (black, blue and red). Results showed that 2 minutes spay and 45 minutes without spay increased number of leaves and shoot fresh weight much higher than 2 minutes spray and 30 minutes without spray. Study of light quality in the root zone showed that black color of the containers, by increasing total leaf area and shoot dry and fresh weight, was the best color treatment. Blue color in the root zone had the most influence on final root length; but was not able to increase root dry and fresh weight, because of higher number of roots in other color treatments. In general, spraying nutrient solution for two minutes, and 45 minutes without spray, along with black color containers in the root zone was the best treatment for most growth characteristics of the anthurium plant.

An experiment was carried out to compare the vase life and factors affecting the longevity of 10 cut rose cultivars imported to Iran. The vase lives of these cut rose cultivars were compared in preservative solution containing hydroxyquinoline citrate (HQC) plus sucrose. Results showed that there was significant difference among cultivars in vase life, time of flowering, water uptake, evaporation rate, ethylene production and carbohydrate content. Maroussia flowers had the longest vase life (18.3 days) and ‘Black magic’ had the shortest vase life (7.6 days). Cultivars with longer vase life had higher concentrations of soluble carbohydrates (fructose, glucose and sucrose) in petals as compared with cultivars that had shorter vase life. Also, short-lived cultivars produced higher ethylene rate than long-lived cultivars.

Soil and water resources are limited and optimal use of water resources in agriculture requires accurate determination of water consumed by plant species in different circumstances. This situation is necessary more than ever due to fast development of greenhouse cultivation. In this regard, to determine evapotranspiration and crop coefficient (KC) of greenhouse cucumber, two microlysimeters were installed for growing cucumber and grass. Daily evapotranspiration rate of both plants was measured by weighing method. Also, by using meteorological data, recorded inside the greenhouse, the reference crop evapotranspiration was calculated with Penman-Monteith-FAO, Hargreaves-Samani and Makkink methods. Evapotranspiration of cucumber plants, with plant spacing of 40×70 cm, during the 4-month growth period was measured as 273.2 mm. Mean values of KC for cucumber in greenhouse was 0.14 in the initial stage of growth, 0.78 in the development stage, 1.37 in the middle stage and 0.86 in the last stage. Also, crop coefficient values for reference crop evapotranspiration estimated by the Hargreaves-Samani and Makkink methods were closer to the actual values. The Penman-Monteith-FAO equation estimated Kc value about 1.6 to 5 times higher than the actual value.