نشریه روابط خاک و گیاه
پیاپی 1 (بهار 1389)

Abstract This research was performed in a completely randomized block design with four replications to investigate zinc (Zn) and manganese (Mn) nutrition effects on greenhouse tomato (Lycopersicon esculentum Mill. cv. HAMRA) in a perlite-containing media. Experimental treatments were: (1) control (Mn and Zn-free nutrient solution), (2) application of Mn in a concentration equal to the full Hoagland’s nutrient solution (4.06 mg/l), (3) application of Zn in a concentration equal to the full Hoagland’s nutrient solution (4.42 mg/l), (4) application of Mn and Zn in concentrations equal to the 50% Hoagland’s nutrient solution (2.03 mg/l Mn + 2.21 mg/l Zn), and (5) application of Mn and Zn in concentrations equal to the full Hoagland’s nutrient solution (4.06 mg/l Mn + 4.42 mg/l Zn). Results showed that the highest fresh-fruit yield, fruit and leaf dry matter and content of Mn and Zn in fruit were obtained from single or combined application of Mn and Zn in concentrations equal to the full Hoagland’s nutrient solution. In addition, Zn and Mn nutrition significantly affected the fruit concentrations of crude protein, nitrogen and phosphorus, while the effect of these treatments on fruit size of tomato was not significant.

This study was conducted to evaluate drought resistance of milk thistle (Silybum marianum L.) at seedling stage. The experiment was designed as a split plot in a randomized complete block design. Treatments were combination of drought stress levels as main plots and different milk thistle ecotypes as subplot layouts replicated 3 times and run in a hydroponic system. Root length, root volume, chlorophyll content, electrolyte leakage and dry weight of root were measured for assessing the ecotypes. Results showed that there were significant differences between the measured traits at 1% level. Significant interaction between stress and ecotypes, indicated that the ecotypes had different trends over stress levels. Mean comparison of ecotypes suggested that decreased chlorophyll, root tolerance index, root volume and dry weight and increased electrolyte leakage were related to the increased stress intensity. Values of root tolerance index and electrolyte leakage suggested Ghaemieh as a drought tolerant ecotype. Correlation among root characteristics and root tolerance index showed that root volume and dry weight are more efficient criteria, compared to root length, for evaluation of drought tolerance in milk thistle genotypes.

Hydroponic growth systems are expanding due to their advantages such as maximum yield, healthy crop production and reduced labour requirement. Vegetable in each stage of the plant growth needs adequate nutrients in different growing media. The objective of this study was to examine the effect of some growth media on N, K and Mg uptake by greenhouse cucumber. This study was carried out in the research greenhouse of Islamic Azad University-Khorasgan branch, using a completely randomized design with 5 treatments, 4 replications and 10 plants in each replication. The Five different growth media consited of pure cocopeat, perlite-cocopeat (50-50 v/v), perlite-cocopeat-peatmoss (50-20-30 v/v and 50-30-20) and perlite-peatmoss. Physical and chemical properties and some nutrients concentrations such as N, K and Mg as well as fruit yield were examined. Although no significant difference was found among the studied growth media in the fruit yield of cucumber, the highest yield was obtained for cocopeat. Significant difference (P < 0.05) was observed in the plant biomass among the growth media. The highest biomass was obtained for the cocopeat and perlite-cocopeat media. No significant difference was found among the growth media in concentrations of N, K and Mg although the highest concentrations of N and K in the second and third stages of sampling were obtained in cocopeat. Shoot concentration of Mg at the first and second stages of sampling was more than the critical deficiency level. The best concentration of Mg was obtained in cocopeat. In general, the best nutrient concentration and yield were found in cocopeat substrate which can be used as an appropriate growing cucumber media for in soilless culture.

The effects of different levels of nitrogen (100, 200, 300 and 400 mg/L) and potassium (125, 250 and 375 mg/L) on yield and leaf N and K concentrations of tomato were investigated in perlit culture using a factorial randomized design with three replications. The highest fruit yield was obtained with 200 mg/L N. Higher levels of nitrogen decreased tomato yield. With increasing nitrogen concentration in nutrient solution, N content of leaf increased significantly whereas leaf K concentration decreased. Different potassium levels had no significant effect on tomato yield. With increasing potassium levels of nutrient solution, concentration of leaf N decreased significantly whereas concentration of leaf K increased. The greatest and the least fruit yields were obtained from N200K250 and N400K375 treatments, respectively. The highest and the lowest concentrations of leaf N were observed in N400K125 and N100K375 treatments, respectively. The greatest and the least concentrations of leaf K were observed in N100K375 and N400K125 treatments, respectively.

Silicon (Si) has beneficial effects on the growth, yield, and tolerance of some crops against biotic and abiotic stresses. Considering the absence of Si in the nutrient solutions used in hydroponically-grown cucumber, the present study was conducted to investigate the influence of Si on the growth and yield of two cucumber genotypes (Cucumis sativus L. cvs. Dominus GRC and Super Dominus). In a hydroponic experiment, two cucumber cultivars were exposed to three Si levels (0, 100, and 200 mg L-1 Si in the form of sodium silicate). The results showed that supplement of Si in the nutrient solution increased Si concentration in cucumber root and shoot. The root and shoot dry weight, crop height, and root length of cucumber plants were significantly (P< 0.05) greater in the presence of Si in comparison with the free- Si treatments. Most of the growth parameters, did not have significant difference at the 100 and 200 mg L-1 silicate levels. According to the results of the present study, it seems that the application of 100 mg/L Si in the nutrient solution could improve the growth and yield of cucumber.

In order to study the effect of nitrogen form and pH of nutrient solution on the shoot concentration of P, nitrate, organic N + inorganic ammonium, and total N of spinach, a factorial experiment was conducted with two factors including pH of nutrient solution in three levels (4.5, 6.5 and 8.0) and nitrate to ammonium ratio of nutrient solution in five levels (100:0, 75:25, 50:50, 25:75 and 0:100). This factorial experiment was carried out in a completely randomized design with four replications. Three seedlings of spinach plant (Spinacia oleracea L. Sirius cultivar) were cultivated per pot and were nourished with 15 different nutrient solutions. The results showed that while the effect of nutrient solution pH on the shoot concentration of P, nitrate, and organic N + inorganic ammonium was significant, it was not significant on the shoot concentration of total N. By increasing the nutrient solution pH from 4.5 to 8.0, the shoot concentration of P and nitrate was significantly decreased, but the shoot concentration of organic N + inorganic ammonium, and total N did not change significantly. The main effect of nitrate to ammonium ratio of nutrient solution on the shoot concentration of P, nitrate, organic N + inorganic ammonium, and total N of spinach plant was significant. By increasing the ammonium concentration of nutrient solution, the shoot concentration of nitrate was significantly decreased, while the shoot concentration of P, organic N + inorganic ammonium, and total N of spinach plant was significantly increased. The effect of N form of nutrient solution on the shoot concentration and content of P, nitrate, and total N of spinach plant was dependent on the nutrient solution pH and vice versa. The greatest P concentration in spinach shoots was obtained in nitrate to ammonium ratio of 0:100 and pH of 8.0. The greatest spinach shoots nitrate concentration was found in nitrate to ammonium ratio of 100:0 and pH of 8.0, while the greatest concentrations of organic N + inorganic ammonium and total N in spinach were observed in nitrate to ammonium ratio of 25:75 and pH of 6.5.

Most plant species are sensitive to high ammonium concentrations. In this experiment the sensitivity of lettuce and spinach to ammonium was investigated. In a factorial experiment with framework of a completely randomized design with two factors, nitrogen form (ammonium and nitrate) and plant species (lettuce and spinach), and three replications seeds were germinated in a mixture of perlite, sand and clay in soil-maid pots. After two weeks, the seedlings at two true-leaf stage were then transferred to buckets containing 4 L of aerated nutrient solution. The four plants were growing together. The treatments were ammonium and nitrate at 5 mM. In comparison to nitrate, ammonium reduced the growth of both species. Concentration of K, Mg, and Na decreased with ammonium in both species. The reduction of K and Mg concentrations in ammonium-fed plants may have a role in ammonium toxicity. Ammonium nutrition of both species caused an increase in P at roots and shoots. Higher P content at ammonium-fed lettuce and spinach plants may be due to creation of cations and anions balance in plants. Chlorophyll a and b were higher in ammonium-fed than nitrate-fed plants.