Mohammad Kazem Souri

Sucrose functions as a transported sugar and carbon carrier between source and sink tissues in plants, influencing numerous growth processes and physiological events. To examine the effect of foliar‐applied sucrose on carbohydrate allocation and biomass distribution in different cauliflower organs, a factorial experiment was conducted using a completely randomized design (CRD) with four replications. The first factor was sucrose foliar application at two levels (0% and 1%), and the second factor was six plant growth stages: (1) 8–14 true leaves; (2) 14–20 true leaves; (3) more than 20 true leaves up to curd initiation; (4) curd formation stage; (5) curd diameter reaching 50% of the expected size; and (6) harvestable dense curd. Results showed that leaf carbohydrate concentration was initially low but gradually increased, peaking at stage 4. As the plant transitioned to the reproductive phase, carbohydrates were increasingly translocated to the curd, leading to a significant reduction in leaf carbohydrate content, particularly evident at stage 6 compared to stages 4 and 5. At stage 3, just before the reproductive phase, the leaf‐to‐plant weight ratio was highest. However, a sharp decline in this ratio was observed after curd initiation (stage 4), continuing through stage 5. At the harvest stage, analysis of fresh weight distribution among sucrose‐treated plants revealed that the curd accounted for the highest proportion (51.61% of total plant weight), followed by leaves (36.93%), stems (16.38%), and roots (5.18%). In contrast, control plants (no sucrose application) had the highest fresh weight in leaves (44.21%), followed by the curd (34.75%), stem (15.58%), and root (5.47%). These findings suggest that sucrose foliar application enhances carbohydrate translocation to the physiological sink (the curd), thereby modifying the source–sink relationship by regulating sugar partitioning and physiological processes. The onset of reproductive growth and the initiation of floret development appear to be critical stages when external carbohydrate supplementation—such as foliar‐applied sucrose—is most beneficial and can improve curd yield rather than other phenological stage.

In this study, two experiments were conducted to evaluate the plant response of Brachiaria brizantha cv. MG5 to nitrogen forms and different pH of nutrient solution. For this, nutrient solutions containing ammonium and ammonium nitrate were fixed at pH 4, 6 or 8, and nutrient solution containing nitrate was fixed at pH 6. The pH adjustment was done by different compounds including MES, calcium hydroxide, calcium carbonate and sulfuric acid. In another experiment the seedlings were grown in nutrient solution with different N forms, but without pH adjustment. The results showed that plants in ammonium or ammonium nitrate at pH = 4 had better growth and performance, followed by pH = 6, compared to plants grown at pH = 8 (buffered with calcium carbonate). Calcium carbonate (bicarbonate) especially in higher amounts in nutrient solution (pH = 8) significantly reduced plant growth particularly root growth as the toxic effects were visible on the roots. The adverse effect of carbonate at high pH was more than those at low pH. High concentration of carbonate in presence of ammonium also was toxic for plants probably due to additional toxic effect of ammonia. However, plants were able to grow normally with different N forms under hydroponics culture, independent of pH effect. When pH was not controlled under different N-forms, there was no significant difference between root and shoot biomass production or leaf SPAD value and protein concentration. So, the presence of carbonate but not pH, was determined as an inhibiting factor for growth of Palisadegrass plants.

Background: Soil salinity buildup and soil degradation are emerging challenges in cropping systems practicing high chemical fertilization. Application of biostimulants and organic fertilizers are better deserve agricultural sustainability and are generally reflected in more nutritious foods than chemical fertilization. Materials and methods: In this study, the growth, quality and antioxidant capacity of coriander (Coriandrum sativum L.) were evaluated under application of organic and biological compared to chemical fertilization in a pot experiment. Different soil fertilization treatments including vermicompost (20% pot volume), cow manure (20% pot volume), biophosphate (as seed inoculation), glycine amino acid (as a biostimulant at 300 mg/kg soil), mixed NPK fertilizer (at 600 mg/kg soil) and unfertilized control were applied to plants under a completely randomized design with four replications. Results: The results showed that application of organic fertilizers mainly vermicompost and glycine, and to lesser extent NPK fertilizer significantly increased many growth, yield and biochemical quality traits of coriander including root and shoot biomass, leaf SPAD value, ascorbic acid, mineral nutrients, flavonoids and antioxidant activity compared to control plants. Fertilization practices resulted in higher biomass production of root (all treatments) and shoot (all treatments except biophosphate) than control plants. Leaf minerals including N and K (in vermicompost, NPK and glycine treatments), leaf P and Fe (in vermicompost and glycine treatments), leaf Zn (in vermicompost treatment) were significantly increased compared to control plants. Application of manure recorded the lowest leaf Ca and total phenols, while the highest leaf Ca was in vermicompost and glycine-treated plants and the highest leaf phenols was in vermicompost treatment. Application of glycine resulted in the highest leaf ascorbic acid as well as catalase enzyme activity. Leaf antioxidant capacity was significantly higher in vermicompost, glycine and NPK treatments compared to control plants. Leaf carotenoids, peroxidase activity, the concentration of Mg, Cu and Mn were not significantly affected by treatments. Conclusion: The results indicate that cow manure and biophosphate treatments were not much effective on plant growth; however, vermicompost and glycine showed promising improvement of coriander growth and antioxidant capacity even more than NPK fertilization. Graphic

Humic acid (HA) as a major portion of humic substances and organic matter play an important role in soil fertility and environmental sustainability. Previous studies reported an enormous range of responses after HA application on plants. To investigate the influence of HA on pelargonium plants cv. ‘Hortorum’ this study was conducted as a randomized complete block design under greenhouse condition. Treatments included HA at 0, 250 and 500 mg L⁻¹ concentrations that were added into the soil via irrigation. Application of HA at both 250 and 500 mg/L promoted plant growth characteristics; however, application of 250 mg L⁻¹ of HA showed better improvement in terms of numbers of leaves, numbers of flowering shoots, and numbers of flowers per plant. Moreover, the length and diameter of the flowering shoot, inflorescence diameter, fresh weight of the aerial parts per plant, and leaf nitrogen (N) were improved only by 250 mg L⁻¹ of HA application.

Onion is an important crop with significant roles in human diets. The growth, yield, and quality of vegetable crops, including onions, are more vulnerable to water stress than other crops. In this study, different levels of deficit irrigation (DI) as factor A (a1: 80%, a2: 70%, and a3: 60% of soil field capacity [FC]) and humic acid (HA) as factor B (b1: without and b2: with HA application) were evaluated on onion growth characteristics in a factorial design with four replications. The results showed that the interaction of DI and HA was significant on leaf protein, peroxidase (POD), superoxide dismutase (SOD), and on bulb protein and potassium (K) concentrations. The highest record of these traits was observed in a3b2 (highest DI with HA application), and their lowest was in those at first level of DI (a1). Leaf protein and, to a lesser extent, bulb protein were increased by DI and HA applications. DI at 60% but not at 70% FC significantly reduced bulb fresh weight. There was a gradual increase in leaf proline, soluble sugars, protein, catalase (CAT), POD, SOD activity, and bulb K by application of DI; however, most of bulb traits including protein, iron (Fe), zinc (Zn), and CAT and POD activity were increased only under highest DI level (a3: 60% FC). However, application of HA further increased the soluble sugars and protein concentration as well as the POD and SOD activities of leaves, and protein, Fe, K concentrations, and CAT activity of bulbs under DI. The results indicated that HA benefitted onion growth particularly under DI conditions.

Background: Different approaches have been used to improve mineral nutrient status of plants in absence of chemical fertilization and toward safer products and improved human health. Amino acids have been proposed with such roles in different recent studies. In this study, glycine was applied as foliar (250, 500 and 1000 ppm) or as soil (250 and 500 mg/plant) to cucumber plants compared to unfertilized control and NPK fertilization, under greenhouse conditions. Results: The results showed that all glycine treatments increased leaf area and the economic life of plants compared to control. Soil application of glycine at higher concentration of 500 mg/plant was able to produce the same or better records than NPK fertilization, particularly regarding leaf mineral concentration, plant economic life and total yield. Leaf macro- micro-nutrients were most increased under 500 mg soil-glycine application. Foliar spray of 500 ppm glycine resulted in better records than the other two levels, as spray of 1000 ppm glycine showed adverse and toxic effects including leaf necrosis. Fruit firmness was increased only by NPK and soil application of 500 mg glycine, whereas fruit vitamin C was increased by NPK fertilization, soil application of glycine at both levels (250, 500 mg) and foliar application of glycine at 500 ppm compared to control plants. Conclusion: The results indicate that soil application of 500 mg glycine/plant was able to improve leaf mineral and physiological characteristics towards higher yield and quality.

Compost produced from sugarcane bagasse was substituted at a range of different concentrations into soil bedding medium mixture, to evaluate their effects on the growth of Pelargonium × hortorum. Plants were grown in a substrate mixture (25% leaf compost; 25% cow manure; 50% garden soil (volume) as control and substitution with different rates of sugarcane bagasse compost of 20%, 30%, 40%, 80% and 100% were applied in three replications. The results showed that application of sugarcane compost started to stimulate plant growth at 20% level and continued over other levels; however, there was no significant difference among sugarcane compost levels regarding many growth traits. Application of low rates particularly 20% resulted in the highest record regarding many morphological traits including number of leaves, lateral stems, flowering shoots, flowers, inflorescence diameter, main shoot diameter, shoot and root biomass, and phosphorus concentration. Moreover, nitrogen and potassium concentrations were highest at 40% treatment. A positive increase in chlorophyll a but not chlorophyll b was found by application of all levels of sugarcane compost compared to control plants.

Growth Characteristics and Fruit Quality of Chili Pepper under Higher Electrical Conductivity of Nutrient Solution Induced by Various Salts

Background: Contamination of vegetable crops with heavy metals is a great threat to human health. On the other hand, monitoring plant tissue content of heavy metals at different growth stages could have important implications. In this study, shoot and root samples of garden cress and sweet basil were collected from five farms, from heavy metal polluted fields located in Shahre Rey, south of Tehran, Iran, in either young (3 weeks old) or mature (7 weeks old) plants. The concentrations of cadmium (Cd), lead (Pb), nickel (Ni), arsenic (As), chromium (Cr), cobalt (Co), copper (Cu), manganese (Mn) and zinc (Zn) in plant tissues were determined using atomic absorption spectroscopy. In another study, 2 weeks (young) or 6 weeks old (mature) plants of garden cress were subjected to three concentrations of Cd and Pb (0, 5, 10 mg L⁻¹) under hydroponic sand culture for 5 days, in which Hoagland formula was used for nutrient solution preparation. Results: The results showed that root concentration of various heavy metals, particularly Cd, As, Ni, Co, Cu, Mn and Zn but not Pb were significantly higher than their shoot concentration in either crop under field sampling. The leaf concentration of some heavy metals was significantly different in seedling and older (mature) plant samples of either crop. Young plant leaves of sweet basil had significantly less Cd, Pb, As and higher Cu than mature plants, whereas young garden cress plants had similar Cd, Pb and higher As and Zn concentrations than mature plants. The Cr, Co, Mn and Zn concentrations were similar in young and mature plants of sweet basil. The Mn, Co, Cr and Ni concentration of young and mature plants of either crop was also similar. The result of hydroponic study showed that young plants of garden cress had higher potential to accumulate lead in shoot and root, particularly in lower (5 mg L⁻¹) than higher (10 mg L⁻¹) lead concentration; however, root Pb concentration at 10 mg L⁻¹ Pb of nutrient solution showed no difference between young and mature plants. Regarding cadmium, young garden cress plants accumulated higher Cd than mature plants in their shoot, particularly under higher Cd levels (10 rather than 5 mg L⁻¹) of nutrient solution; however, a wide difference in root Cd concentration was observed under low (5 mg L⁻¹) than higher (10 mg L⁻¹) cadmium concentration of nutrient solution. Conclusion: The results of these two studies indicate that despite that young plants have a higher potential for heavy metal uptake and accumulation, the low difference in young and mature plants in the polluted fields may be due to the longer period of plant growth of mature plants that may increase the risk of exposure to polluted air and dust deposition containing high levels of heavy metals.