Greenhouse Plant Production Journal

Abstract This research, conducted in 2023, identifies onion seedling  production key challenges and explores two onion cultivars (Ramhormozi and Primavera) and four density levels {1, 2, 6, and 12 plants in a cell} in a factorial arrangement with three replications. The study focuses on current agricultural practices, the effectiveness of existing methods and the agricultural factors influencing onion seedling farming such as two treatments cultivar and density. A analysis of variance using SPSS software version 21 revealed that the interaction between cultivar and density had a significant impact on most of the traits examined. Each trait showed a different response to these two treatments. The highest and lowest leaf area index were observed in the Primavera cultivar at 6 plants (9.4 m²) and 1 plant (0.33 m²), respectively. So that the quantitative changes are 28 fold. The highest fresh aerial height weight was recorded in the Ramhormozi cultivar at 1 plant (7.6 g), while the lowest was in Primavera at 12 plants (1.7 g). The quantitative changes  in fresh aerial weight are 4.47 fold. The Primavera cultivar at 1 plant (1.66 mg/g) and 12 plants (0.65 mg/g) had the highest and lowest total chlorophyll content, respectively. The quantitative changes in total chlorophyll are 2.5 fold. Also, The results of the correlation analysis among the studied traits in this experiment revealed significant correlations between the morpho-physiological and biochemical traits. The research demonstrated that hydroponic onion cultivation with hoagland nutrient solution under two treatments of planting density and cultivar had a significant effect on the growth and functional characteristics of onion seedlings. In general, it can be concluded that marketable and healthy onion seedlings are produced at high densities and in different cultivars using the flotation system. This cultivation method can, as an efficient production system, compensate for the limitations of onion seedling production in uncultivable lands.

Abstract The rise in global temperatures, resulting from global warming, imposes severe stress on plants, hindering their growth and development. This study aimed to investigate the effects of melatonin and sodium nitroprusside (SNP) on the growth of California Wonder green bell pepper under heat stress conditions. A factorial experiment using a completely randomized design with three replications was conducted. Plants were exposed to temperatures of 25°C (control), 35°C, and 40°C for 24 hours following foliar application of 0 µM, 50 µM, or 100 µM melatonin and SNP. Results showed that 100 µM melatonin increased shoot dry weight by 13.26% compared to the control. Under heat stress, leaf nitrogen content increased by 32.73% and 37.24% with 50 µM and 100 µM SNP, and by 9.61% and 23.72% with 50 µM and 100 µM melatonin, respectively. At 40°C, leaf potassium levels rose significantly—up to 72% with 100 µM SNP. Additionally, 100 µM SNP increased copper and iron levels by 17.96% and 202.98%, respectively. Foliar spraying with 100 µM melatonin improved photosynthetic traits (carotenoid and carbohydrate contents) and reduced malondialdehyde levels, enhancing stress tolerance. Hydrogen peroxide content decreased by 15.16% and 20.99% with 50 µM and 100 µM SNP, respectively, at 40°C. Both melatonin and SNP significantly enhanced the activity of antioxidant enzymes (superoxide dismutase, ascorbate peroxidase, and guaiacol peroxidase) under heat stress. Overall, 100 µM melatonin was most effective in mitigating heat-induced damage and improving the physiological and biochemical performance of green bell pepper seedlings.

Abstract Soil alkalinity is a major constraint to agricultural production worldwide, as only a limited number of plant species . Nitrogen sources significantly influence the pH of the nutrient solution. This study was conducted as a factorial experiment based on a completely randomized design with three factors: sodium bicarbonate at three concentrations (0, 10, and 20 mM), nitrogen source at three levels (ammonium sulfate, ammonium nitrate and calcium nitrate at a concentration of 5 mM), and two garlic genotypes (white and purple), with three replications in a hydroponic greenhouse at the Faculty of Agriculture, Vali-e-Asr University of Rafsanjan. Also, the results showed that increasing sodium bicarbonate concentration led to a decrease in morphological parameters. Manganese and sodium concentrations increased with higher sodium bicarbonate levels, particularly under calcium nitrate and ammonium sulfate treatments. Ammonium nitrate also increased iron and copper concentrations. Additionally, ammonium sulfate and calcium nitrate improved nutrient uptake. Based on the findings, the white garlic genotype demonstrated superior performance in most measured traits compared to the purple genotype. The interaction between nitrogen form and nutrient solution pH was shown to influence nutrient uptake efficiency, stress tolerance, and overall plant performance. These findings highlight the critical role of targeted nitrogen management in alleviating the negative impacts of alkaline stress on garlic cultivation. By addressing nutrient imbalances and promoting better growth performance, appropriate nitrogen source strategies can enhance the resilience and productivity of garlic genotypes under hydroponic conditions, thereby supporting more efficient and sustainable agricultural practices.

Abstract With the world's population increasing and a large percentage of this population living in urban areas, the need for efficient and low-consumption agricultural methods is becoming more and more necessary. Vertical farming as a solution to the challenges of food security and environmental change, using vertical spaces and controlled environments, by reducing the consumption of various resources, reducing greenhouse gas emissions and environmental pollution of traditional agriculture, while helping the environment, enables the production of agricultural products. Microgreens, which have high amounts of vitamins, minerals and antioxidant compounds, can be used as a new generation of healthy foods and an ideal option for cultivation in vertical systems. Several factors, including the selection of appropriate species, control of the light spectrum (especially blue and red spectra), temperature, humidity, seed density and type of growing medium, affect the growth and quality of microgreens. Along with its advantages, vertical farming faces challenges such as high initial cost, high energy consumption, limited crop yield, gaining consumer trust, and competition with traditional crops. However, technological advancements and further research will help reduce these challenges and expand vertical farming. This article examines the vertical farming system, especially its potential for producing microgreens.

Abstract Heat stress arises when temperatures exceed a critical threshold for a specific duration during various stages of plant development. Consequently, it is crucial to devise effective strategies to overcome this obstacle in crop production. This research investigates the impact of melatonin and sodium nitroprusside on enhancing the heat resistance of Capsicum annuum. The Wonder cultivar of Capsicum annuum underwent various temperature treatments (25, 35 and 40°C) for a duration of 24h subsequent to being sprayed with melatonin and sodium nitroprusside at concentrations of 50 μM and 100 μM. The findings indicated that the application of melatonin during a temperature treatment resulted in an enhanced efficiency of leaf water consumption (16 percent). Additionally, pepper plants exposed to the same temperature treatment and treated with 100 µM melatonin exhibited a significant 13.5 % increase in fruit dry weight compared to the control group. The application of melatonin and sodium nitroprusside resulted in enhanced fruit characteristics and fruit marketability characteristics decreased. When exposed to a temperature of 40°C, there was a reduction of 18.50 % in the fruit's total soluble solids (TSS) compared to the control temperature of 25°C.

Abstract Global agriculture will face two major challenges in the future: population growth and climate change. One of the primary obstacles to agricultural productivity is environmental stress, with abiotic factors having a considerable negative effect on horticultural yields. As such, exploring effective strategies to mitigate plant stress is essential. Among these strategies, the use of biostimulants has emerged as an innovative and eco-friendly approach to boost growth and productivity in horticultural crops under stress conditions. Biostimulants, including seaweeds, fungi, bacteria, and amino acids, play a key role in alleviating stress effects. Their effectiveness is largely attributed to bioactive compounds such as polysaccharides, pigments, phenolics, proteins, phytohormones, and various micro- and macronutrients. Research indicates that these compounds can significantly reduce plant stress and enhance resilience. The effective use of bio-stimulants can reduce waste from fertilizers and minimize the risk of nutrient runoff that leads to environmental pollution. Economically, it enhances nutrient uptake, plant growth, and productivity under stress conditions, reduces input costs, and increases farmers' profitability. Therefore, the use of these compounds in greenhouse systems is not only environmentally significant but also economically important. This study delves into the application of biostimulants in horticulture under abiotic stress and highlights some of the key challenges associated with their broader adoption and implementation.