Extended Abstract
1. Introduction: Due to the increase in tomato cultivation in greenhouses, the need for organic nutrition to increase the yield and health of the product is more necessary than ever. Sucrose is the main transportable product of photosynthesis in the phloem vessels, which is absorbed through the leaf, and especially in low light conditions, it provides the necessary energy for the growth of reproductive organs and increases the growth of the fruit. The use of natural compounds, such as beet molasses, in combination with sucrose can have positive effects on the quantitative and qualitative growth of tomatoes. Despite the studies of sucrose in the form of foliar spraying in plants, there is little information about the effect of sugar beet molasses in greenhouse conditions. Therefore, in this research, the effects of foliar application of sugar beet molasses on the quantitative and qualitative characteristics of greenhouse tomatoes of the Dafnis variety were studied.
2. Materials and methods: The treatments included sugar beet molasses in concentrations of 0, 5, 10, and 15%, which were applied as a foliar spray one week after plant establishment and repeated once every 10 days. The experiment was conducted in the form of a randomized complete block design with four treatments and three replications. The measured variables included plant height, leaf length, leaf width, fruit firmness, soluble solids, acidity, vitamin C, total sugar, glucose, sucrose, fructose, lycopene, chlorophyll, carotenoid, anthocyanin, total nitrogen, phosphorus, potassium, calcium, and magnesium. Plant height measurement and yield were calculated based on plant height and fruit weight up to the first three clusters of the plant. The test data was analyzed using SAS statistical software. The mean comparisons for each attribute were also done using Duncan's test at the probability level of 5%.
3. Results and Discussion: The results showed that the highest plant height (55.43 cm), fruit firmness (4.23 kgcm2^-1), chlorophyll a (1.4 mgg^-1 FW), chlorophyll b (0.423 mgg^-1 FW), total chlorophyll (1.824 mgg^-1 FW), and anthocyanin (0.216 µg^-1 FW) were related to the 10% sugar beet molasses. The highest fruit yield (1600 g per plant) was related to the 5% molasses, which was statistically not significantly different from the 10% molasses. The findings of phytochemical compounds revealed that the highest amount of soluble solids (5.03%), vitamin C (2.38 mg/100 ml of fruit juice), and lycopene (122.11 mgg^-1) was found in 10% molasses sugar beet has been theitized. Also, the highest amount of total sugar (26.13 mgg^-1), glucose (7.36 mgg^-1), sucrose (4.12 mgg^-1), and fructose (1.92 mg/g) was observed in 10 % of molasses. The highest amount of total phenol (15.95 mgg^-1), flavonoid (2.71 mgg^-1), and antioxidant (61.48%) was related to the 10% molasses. The highest amount of nitrogen (3.8%), phosphorus (0.328%), potassium (4.04%), calcium (2.62 mgg^-1), and magnesium (2.14 mgg^-1) was obtained in foliar application of 10% molasses. Tomato is a light-demanding plant, so light is the limiting factor in its greenhouse production. During the winter months, due to the short day length and low radiation intensity, the amount of light received during the day is greatly reduced, which causes the reduction of greenhouse tomato yield. Sugar compounds can have a positive effect on the increase of photosynthetic pigments. Therefore, foliar application of molasses can improve the chlorophyll concentration, and at the same time, it does not cause photosynthetic inhibition in low light conditions of the greenhouse. External foliar spraying of beet molasses causes foliar absorption of sugar and can help tomato plants as an effective method, especially in conditions of low photosynthetic production. Soluble sugars, especially sucrose, glucose, and fructose, play an important role in plant structure and metabolism.
4. Conclusion: In general, the results of this research showed that the amount of photosynthetic pigments, anthocyanins, soluble sugars, antioxidant compounds, and macro elements in 10% sugar beet molasses was significantly higher than the control. The 5% molasses increased the yield and finally the weight of the tomato fruit. The role of sugar beet molasses becomes effective when the plant is exposed to the stress of a lack of light (such as greenhouse conditions in the winter months), because photosynthetic production is limited in the stress of light deficiency. Future research should be focused on sugar transporter minerals such as potassium nitrate and magnesium nitrate. In this experiment, evidence was presented that sugar beet molasses changes the biochemical reaction of tomato to increase fruit quality and total yield.