مجله علوم باغبانی ایران
سال چهل و دوم شماره 3 (پاییز 1390)

In order to investigate and reduce the alternate bearing in Satsuma mandarin (Citrus unshiu), an experiment was conducted in a randomized complete block design of 6 treatments and 5 replications and for a duration of 4 years. Treatments included: 1. Control (optimal application of mineral nutrients as based on leaf analysis and yield); 2. Autumn nitrogen application; 3. Spring pruning; 4. Summer urea spraying; 5. Winter urea spraying; 6. Urea spraying along with autumn nitrogen application, as well as spring pruning. Results obtained for the first year revealed that the highest yield belonged to treatment 6 with 274 kg of fruit per tree, while control yielding 214 kg per tree. During the second year, the highest yield was also obtained from treatment 6, i.e. 198 kg per tree compared with 65 kg in control. During the third year of the experiment which was an "off year", the highest yield was obtained in treatment 3 with 232 kg/ tree as compared with 84 kg in control. During the forth year being an "on year", the highest yield came from control with an average of 307 kg per tree. The total yields in different treatments during the four years of experiment were then compared. Results indicated that, alternate bearing cycle was alleviated as compared with the trees in control. However, in treatment 6, the alternate bearing cycle was almost disappeared with the total yield reaching an acceptable level during all the four years. The index of alternate bearing was calculated for all the treatments with the results indicating that treatment 6 bore the lowest while control had the highest index among all the treatments. So, as observed for treatment 6 (urea spraying with autumn nitrogen application and spring pruning) in which alternate bearing got almost balanced with an increase in total annual yield of acceptable level, this treatment could be considered as an economical, and profitable practices in citrus gardens in north of Iran.

Effects of different K/Ca ratios on the growth, yield and physiological characteristics in Galia (Cucumis melo var. reticulatus L. Naud. cv. Galia) grown in hydroponics were evaluated. The experiment was arranged in a completely randomized design of three replicates. Melon seeds were sown in a medium containing perlite and vermiculite (3:1 V:V) and then irrigated with water containing different K/Ca ratios of: 1.5, 2, 2.5, 3, 3.5, 4. The yield and such plant's physiological characteristics as chlorophyll index and petiole nitrate were assessed. Plants were finally cut and such vegetative characteristics as leaf area, fresh and dry weight measured. The results revealed that the melon yield was significantly affected by various K/Ca ratios, so that the highest yield was observed in ratio 3 (6.25 kg/ per plant), while the lowest was for ratio 4. Leaf area (LA) was significantly affected by various K/Ca ratios, with maximum LA achieved for ratio 3. A positive correlation was observed between leaf area and yield (R2=0.62). The fresh and dry weight of leaf and stem as well as petiole nitrate content were significantly affected by various K/Ca ratios. The percentage of Total Soluble Solids (TSS) was significantly affected by various K/Ca ratios, with the maximum TSS being achieved for the ratio 4 treatment. It was finally concluded that K/Ca ratio 3 treatment was the most effective in improving the growth, yield and physiological characteristics of Galia, so that the adjustment of K/Ca ratio in the nutrient solution at this level seems to be fundamental in obtaining the highest and optimum yield.

RAPD markers were employed to assess the genetic diversity of 34 Iranian wild edible asparagus (A. officinalis) genotypes as well as cv. Mary Washington and A. persicus. In total, 80 RAPD primers were employed for PCR reactions, among which, 18 revealed reasonable polymorphism. The 18 primers produced 175 bands, of which, 160 were polymorphic (91.4% polymorphism). Cluster analysis of the genotypes was performed based on their presence (1) or absence (0) of the bands, employing Jaccard's Similarity Coefficient and the method of UPGMA. The highest and lowest observed genetic coefficients of similarity between genotypes were recorded as 0.71 and 0.29, respectively. At a distance of similarity of 0.68 on the dendrogram, the genotypes were divided into seven sub-clusters. Wild genotypes were positioned in four subclusters followed by two subclusters that included the cultivated asparagus and the edible A. officinalis cv. Mary Washington. The species A. persicus, as a distinguished ones, located in a last subcluster with an acceptable distance from other genotypes. The examined genotypes were of relatively high diversity, indicating the richness of asparagus genetic resources in Iran. Furthermore, this study reflected the capability of RAPD markers in differentiating Asparagus species and to study their genetic diversity.

To study the effects of biofertilizers on physiological and morphological characteristics, as well on essential oil content in Dragonhead (Dracocephalum moldavica), an experiment was conducted at Tarbiat Modares University in 2009. The studied factors were: Vermicompost (0, 15, 30% V/pot), Azotobacter (inoculated and non-inoculated), and phosphatic biofertilizer (inoculated and non-inoculated). The experiment design was a factorial based on randomized complete block design of twelve treatments and four replications. Results revealed that Vermicompost fertilizer significantly affected seed emergence speed (11.94 days), flowering (88.81 days), plant height (50.05 cm), fresh and dry yield (44.56 and 12.049 gr), photosynthesis rate and chlorophyll content, essential oil content (0.74%) as well as essential oil yield (0.34 mlit/pot). Maximum seed weight per plant (4.47 gr) was obtained for BV15. Biophsphate also showed significant effects on seed emergence and chlorophyll content. Interactions of the two factors of Biophosphate inoculation and Vermicompost fertilizer were also significantly affected the plant's dry weight, seed weight per plant, photosynthesis rate as well as the chlorophyll content.

Iran, with a long history of apricot cultivation is one of the most important apricot producers in the world. Centuries of sexual reproduction via seed, have developed many divergent variations of apricots in Iran. However, unfortunately there is no comprehensive report available concerning its diversity and genetic make-up. In this study, 39 Iranian apricot cultivars as well as accessions, native to Iran, were evaluated using morphological and RAPD molecular markers. Total Soluble Solids (TSS), Titrable Acidity (TA), kernel weight, fruit flesh weight as well as fruit weight exhibited high diversity coefficients, making it possible to select for desirable characters in breeding programs. In addition, factor analysis was performed to determine the number of the main factors. A 79.52% level of total variance was explained by the first six factors for morphological discrimination, the first independent factors of which included fruit size (24%), pit (16%) and flavor (14.5%). Cluster analysis of morphological traits led to a separation of cultivars according to their fruit size, ripening season as well as characteristics related to fruit taste. According to the RAPD, the highest genetic similarity was observed between ‘Noori-Dirras’ and ‘Noori-Pishras’ (0.95) while the lowest between ‘Tanasgol’ and ‘Shahrood-48’ (0.3). In the cluster analysis, at similarity distance of 65%, cultivars were placed in six main groups, in agreement with some other results obtained from morphological analysis and from the geographical origins of accessions.

In order to determine the effects of zinc foliar application on the vegetative characteristics, yield and fruit quality in strawberry (Fragaria × ananassa Duch) cv Kordestan under salinity stress conditions, an experiment was carried out hydroponically in glasshouse as a controlled environment during 2009 through 2010. Three levels of NaCl (0, 15, 30 mM) and three levels of Zn (0, 1.5, 3 g/L) were applied in a completely randomized design of three replicates. The results showed that number of leaf, leaf area, fresh and dry weight of leaf and of root, yield characteristics, chlorophyll index and leaf relative water content were reduced in the conditions of salinity, while foliar application of Zinc could increase them, significantly. The proline content of leaf under salinity as well under the interaction effect of Zn and salinity was increased, but of an application of Zn did not affect those parameters. Electrolyte leakage increased by increase in NaCl concentration and decreased with foliar application of Zn. Both salinity and Zn treatments increased the acidity in fruit, but other quality characteristics were not affected by those treatments. It can be concluded that, application of Zn could alleviate salinity stress on strawberry.

Heavy metal hyperaccumulators have recently attracted considerable attention in remediation of an area's pollutants. Lead (Pb) is one of the main pollutant heavy metals that its relatively high concentration have been reported in some environments. In present study, the potential of turfgrass tolerance, regarding seed germination and plant establishment were evaluated, in different concentrations of lead. In an initial stage, the application of Pb(NO3)2 at 0, 200, 400, 800 and 1000 mg/l was tested on seed germination. During the second stage, the effect of a supplement of 0, 200, 400 and 800 mg/l of Pb(NO3)2 concentrations to soil was studied on plant establishment. Some traits including percentage of and germination rate, plumule and radicle lengths, shoot and root lengths, shoot and root fresh weights, shoot and root dry weight, leaf width, leaf chlorophyll content and lead accumulation in shoot and root were recorded. Results revealed that the germination percentage and shoot length increased with increase in lead concentrations in comparison with control, while there was an inhibition effect observed on root growth. The growth factors were not affected by different concentrations of lead in establishment stage in the case of turfgrass. Pb accumulation level in roots was higher than that in shoots. The extent of accumulated Pb in turfgrass tissues increased by increasing Pb in the soil. In total, ryegrass and Kentucky bluegrass accumulated the least (473/5 mg/kg) and the most (1121/5 mg/kg) level of Pb in their shoots, respectively. However bermudagrass and ryegrass showed the least (877/9 mg/kg) and the most (2743/2 mg/kg) lead accumulation in their roots, respectively. An evaluation of the different plant's tolerance and accumulating potential indicated that ryegrass could be employed as cover plant as well as a lead hyperaccumulator plant in remediation of polluted areas.

Oilseed pumpkin is an introduced medicinal plant, the seeds as well as some other organs of which are being utilized in treating an array of human diseases in Iran. Considering the plant's significance in the health product's industry on the one hand, and the countrywide drought stresses and a lack of information on mineral nutrition of the oilseed pumpkin, the present study was aimed to study the impact of irrigation regime as well as N application on chlorophyll (Chl) content, gas exchange properties, proline content, yield and yield components of this useful medicinal plant. A 5-replicate split plot, randomized complete block experiment was conducted at the Lavark Research Farm, College of Agriculture, Isfahan University of Technology-Isfahan, Iran in 2009. Three irrigation regimes based on evaporation from a Class-A Standard Evaporation Pan including irrigation after 65 mm (I1=control), 95 mm (I2¬= moderate water deficit) and 130 mm (I3= severe water deficit) were assigned as the main plots. Three nitrogen (N) application rates including zero N (N1= control), 120 N (N2) and 220 N (N3) kg ha-1 of N as urea were chosen as subplots. Leaf Area Index (LAI), gas exchange attributes, Chl and proline content, fruits/plant, seeds/fruit, 1000-seed weight, fruit and seed yields, oil content as well as yield were evaluated. I1¬ and I3 irrigation levels with 2.11 and 1.46 and N3 and N1 nitrogen levels with 2.50 and 1.16 produced the highest and lowest LAI, respectively. Water deficit stress and lowered N application led to significant decreases in leaf Chl content. Water deficit led to decreases in the net photosynthetic rate (A) and leaf stomatal conductance (gs) but it led to increases in internal CO2 concentrations (Ci). While A and gs increased with N application rate, Ci decreased with an increase in N application. Proline content increased with both increases in water deficit stress and N application rate. I3 irrigation level led to 23, 33, 5, 51, 52 and 55 percent decreases in the traits of: fruits/plant, seeds/fruit, 1000-seed weight, seed and fruit yield as well as oil yield, respectively, as compared with the I1 level. N3 level of nitrogen application resulted in 28, 22, 27, 9 and 33 percent decreases in fruits/plant, fruit and seed yield, oil percent as well as oil yield, respectively, as compared with the N1 level. It could be concluded that the negative impact of water deficit stress on yield and its components in oilseed pumpkin is mainly through the decreases in the photosynthetic surfaces, photosynthetic rate and as well as Chl content. Furthermore, application of 220 kg ha-1 of N may lead to increases in LAI, Chl and A, though the latter increases, seemingly, enhance the growth of vegetative organs rather than the reproductive ones and grain yield components.

The influence of water deprivation on potted grape (Vitis vinifera L.) was investigated. Leaf Mass Area (LMA) and biochemical responses, including chlorophyll, total protein, peroxidase activity, soluble carbohydrates, photosynthesis and stomatal conductance were assessed in leaves of ‘Sahani’ and ‘Bidane sefid’ grape cultivars subjected to progressive drought (soil water potentials of: -0.2, -0.6, -1 and -1.5 MPa). The results indicated temporary reduction in the level of chlorophyll content under drought stress conditions. ‘Sahani’ contained a higher level of chlorophyll in comparison with ‘Bidane sefid’. Leaf Mass Area (LMA) was significantly decreased in ‘Bidane sefid’ under drought stress. LMA in ‘Sahani’ was recorded as higher than in ‘Bidane sefid’. Protein content was significantly reduced in -1 and -1.5 MPa treatment as compared with control (-0.2MPa), and the -0.6 MPa treatment. Peroxidase activity increased with increase in soil water potential. Increase in peroxidase activity in ‘Sahani’ was higher than in ‘Bidane sefid’ in comparison with control. The study revealed that mild drought stress (-0.6 MPa) affects photosynthesis while moderate (-1 MPa) and severe (-1.5 MPa) drought stresses affected chlorophyll, protein, peroxides activity as well as soluble carbohydrate levels. The results, in total indicated that ‘Sahani’ was of a higher tolerance to drought conditions as compared with ‘Bidane sefid’.

Nitrogen forms exert significant effects on physiological and morphological characteristics of plant. In this study, the effects of ammonium, nitrate, and ammonium-nitrate on pepper plants were investigated in soil culture, as well as in solution culture. In the soil culture, 3, 4-dimethylpyrazole phosphate (DMPP) was used as a standard nitrification inhibitor to guarantee the presence of ammonium inside the soil. The results indicated that, in solution culture, when seedlings, at their early stages, were either treated with ammonium, or a portion of ammonium, plant growth parameters were severely decreased as compared with the nitrate grown plants. However, when seedlings were pretreated in nitrate for two weeks, the relative tolerance of plants to ammonium increased. Plants in soil culture had better tolerance to ammonium nutrition as compared with those grown in solution culture. This was probably due to the buffering action properties of the soil in which NH4+ is absorbed onto the soil colloids and slowly released over the time. This is further supported by better growth characteristics of plants grown in ammonium supplied soil as compared with ammonium-fed plants grown in hydroponics.