با همکاری انجمن علمی منظر ایران
نوع مقاله : مقالات پژوهشی
نویسندگان
1 گروه علوم باغبانی ، دانشگاه شهید چمران اهواز، اهواز، ایران
2 گروه علوم باغبانی، دانشگاه شهید چمران اهواز، اهواز، ایران
کلیدواژهها
عنوان مقاله English
نویسندگان English
Introduction:
Roselle (Hibiscus sabdariffa L.) is an important medicinal and industrial crop widely cultivated in tropical and subtropical regions due to its high nutritional value and rich content of bioactive compounds. The calyces of this plant are extensively used in the food, pharmaceutical, and healthcare industries as natural sources of antioxidants, organic acids, anthocyanins, and phenolic compounds. These secondary metabolites play a key role in determining the nutritional, medicinal, and commercial quality of roselle products. Among agronomic practices, planting date is considered a critical management factor that strongly influences plant growth, yield formation, and secondary metabolite accumulation by determining the environmental conditions experienced during key phenological stages. Synchronizing plant development with favorable temperature and radiation regimes can enhance both quantitative and qualitative traits. In warm and semi-arid regions such as Khuzestan province, inappropriate planting dates may expose plants to excessive heat stress during flowering and calyx development, thereby reducing yield and quality. Despite the increasing interest in Roselle cultivation in Iran, information regarding optimal planting dates under local climatic conditions remains limited. Therefore, this study aimed to evaluate the response of quantitative, qualitative, and biochemical traits of Roselle to different planting dates in the warm and semi-arid climate of Hamidieh County, Khuzestan, Iran.
Materials and Methods:
A field experiment was carried out during the 2023–2024 growing seasons at a research farm located in Hamidieh County, Khuzestan province, Iran. The experiment was arranged as a randomized complete block design with four planting date treatments and five replications. The planting dates included April 14, May 5, May 22, and June 5, which were selected based on common regional cultivation practices to represent early to late planting conditions. Standard agronomic management practices were applied uniformly across all treatments throughout the growing period on the farm. Quantitative traits measured at harvest included plant height, number of lateral branches per plant, number of calyces, and fresh and dry weight of calyces, which collectively reflect vegetative growth, reproductive performance, and yield potential. In addition, several biochemical traits were assessed using standard laboratory methods to evaluate the quality of the harvested calyces. These traits included total phenolic content, total flavonoids, total carbohydrates, ascorbic acid, antioxidant capacity, and anthocyanin content, representing the major bioactive compounds contributing to the nutritional and medicinal value of Roselle.
Results and Discussion:
The results indicated that planting date significantly affected most quantitative and biochemical traits of roselle (Hibiscus sabdariffa L.). The earliest planting date (April 14) resulted in the highest plant height (217 cm), number of lateral branches (18 per plant), number of calyces (215 per plant), calyx fresh weight (2.37 g), calyx dry weight (0.44 g), and calyx yield (1,130 kg ha⁻¹). In contrast, the latest planting date (June 5) resulted in the lowest plant height (78 cm), number of lateral branches (2 per plant), calyx fresh weight (1.37 g), calyx dry weight (0.25 g), and calyx yield (181 kg ha⁻¹). The lowest mean number of calyces (40 per plant) was also recorded on June 5, although it did not differ significantly from the May 5 and May 22 treatments. Calyx dry weight on May 22 (0.42 g) was statistically comparable to that on April 14. Regarding biochemical traits, the highest total phenolic content (33.30 mg g⁻¹) was recorded on May 5, whereas the lowest (24.24 mg g⁻¹) occurred on April 14. Total flavonoid content ranged from 10.51 mg g⁻¹ on June 5 to 12.78 mg g⁻¹ on May 5. Anthocyanin content was highest on April 14 (18.47 mg g⁻¹) and lowest on June 5 (14.83 mg g⁻¹). Antioxidant capacity showed its highest mean value (19%) on June 5 and its lowest value (7%) on May 5. Total soluble carbohydrate content was highest on June 5 (33.06) and lowest on May 5 (18.55), while ascorbic acid content was highest on May 22 (59.45 mg g⁻¹) and lowest on June 5 (37.43 mg g⁻¹). Overall, early planting favored vegetative growth and calyx yield, whereas planting date influenced biochemical composition differently, indicating that the optimal planting date may depend on whether yield or specific quality attributes are prioritized.
Conclusion:
Overall, the findings of this study demonstrate that planting date plays an important role in determining the growth, calyx yield, and biochemical composition of roselle (Hibiscus sabdariffa L.) under the warm, semi-arid conditions of Hamidieh, Khuzestan, Iran. Early planting on April 14 was the most favorable treatment for vegetative growth and calyx production, resulting in the highest plant height, number of lateral branches, number of calyces, calyx fresh and dry weights, and calyx yield. However, the effects of planting date on biochemical traits varied depending on the compound measured. While anthocyanin content was highest in the earliest planting treatment, the highest total phenolic and flavonoid contents were recorded on May 5, and the highest ascorbic acid content was observed on May 22. The highest mean antioxidant capacity and total soluble carbohydrate content were recorded in the latest planting treatment, although the statistical significance of these differences should be considered when interpreting the results. These findings indicate that the planting date that maximizes calyx yield may not necessarily optimize all biochemical quality attributes. Therefore, April 14 can be recommended as a promising planting date when the primary objective is to maximize calyx production under the conditions of this study. Further research evaluating planting date, phenological development, and environmental conditions across multiple locations and growing seasons is needed to confirm this recommendation and identify suitable planting dates for specific yield and quality objectives.
کلیدواژهها English
