Evaluation of the Effect of Ascorbic Acid and Sucrose Foliar Application on some Quantitative and Qualitative Characteristics of Cucurbita pepo var. Styriaca

Introduction Pumpkin (Cucurbita pepo) is a medicinal plant belonging to the Cucurbitaceae family and the order Cucurbitals. The seeds of this plant are a rich source of essential oils and proteins for the body. It is used in the production of various drugs such as Peponen, Pepostrin, Grunfig and treatment of prostate swelling, urinary tract inflammation, atherosclerosis, gastrointestinal regulation, etc. Since the components of medicinal plants are low at natural condition, and could be increased by means of different environmental conditions, nutrition or application of elicitors; thus, it is necessary to work on mentioned parameters effects on quantitative and qualitative attributes of medicinal plants. Recent years, many researches have been done based on natural components for increment of yield and secondary metabolites of medicinal plants. Ascorbic acid is one of these materials which its effect on plant growth has been validated. In the management of agricultural inputs, especially in the cultivation of medicinal plants, the application of substances that have the least harmful side effects on human health and the environment is recommended. Meanwhile, sucrose and ascorbic acid are healthy substances to improve growth and increase crop yield. Therefore, the aim of the present study was to determine the effect of these two substances on yield, yield components and phytochemical characteristics of pumpkins. Materials and Methods  Pumpkin seeds were prepared from Pakan Bazr Esfahan by purity of 99%. Then, planted in a farm of 500 m2 at Behshar. After plant growth, spray treatments were conducted at three times as before flowering, onset of flowering and fruit set stages. This experiment was conducted in factorial with sucrose factor at four levels (0, 5, 10, 15 g.l-1) and ascorbic acid factor at four levels (0, 15, 30, 45 mM), based on a randomized complete block design with three replications. The studied characteristics included number of leaves and fruits, plant yield, 1000-seed weight, total number of seeds, number of healthy seeds, percentage of healthy seeds, number of blank (deaf) seeds, percentage of blank seeds, total chlorophyll, antioxidant activity, phenol, flavonoids, protein and oil percentage. Statistical analysis of data was performed using SAS statistical software and comparison of mean was performed using the least significant difference (LSD) at the level of 5% probability. Figures were graphed with Excel software. Results and Discussion  According to this study results, the effect of foliar application of sucrose and ascorbic acid and their interaction on most of the studied traits was significant. Application of 15 g.l-1 sucrose with 15 mM ascorbic acid increased the number of fruits to 1.68 per plant, which showed an increase compared to the control treatment. The highest total number of seeds with an average of 464 seeds per fruit was obtained by applying 5 g.l-1 sucrose with 45 mM ascorbic acid, which compared to the control (247.33) recorded an increase of 87.60%. The highest total chlorophyll content was measured with an average of 2.081 (mg.g-1 fresh weight) using 5 g.l-1 sucrose with 15 mM ascorbic acid, which showed an increase of 1.81% compared to the control treatment (2.044). Also, application of 15 g.l-1 sucrose along with 15 mM ascorbic acid increased protein by 40.03%, which showed an increase of 79.26% compared to the control (22.33). Other results indicate that increasing the amount of seed oil up to 44.50% is available with the application of 15 g.l-1 sucrose with 30 mM ascorbic acid and also with the application of 10 g.l-1 sucrose with 45 mM ascorbic acid; which had an increase of 16.61% compared to the control (38.16). The results of the present study showed that the application of combined ratios of sucrose and ascorbic acid has been effective in improving the quantitative and qualitative attributes of pumpkin, including protein content and percentage of pumpkin seed oil. Conclusion  Since the treatment of sucrose 10 g.l-1 with 45 mM ascorbic acid significantly affected most of important attributes such as total antioxidant activity, total flavonoids, protein content and high oil content, therefore, this combination of treatment can be applied to increase the quality of pumpkin seeds. However, if only quantity is important, the treatment of sucrose 15 g.l-1 with 15 mM ascorbic acid, which caused the highest number of fruits per plant, the highest yield as well as the highest protein, can be recommended.