Browsing by Author "Sangeetha, K.S"

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    Chitosan elicitation for essential oil yield and quality in Patchouli (Pogostemon cablin Benth)
    (Department of Plantation, Spices, Medicinal and Aromatic Crops, College of Agriculture, Vellanikkara, 2024) Virata, G.; Sangeetha, K.S
    Patchouli (Pogostemon cablin Benth.) belonging to Lamiaceae family is a perennial, branched, erect, aromatic herb possessing quadrangular stems. It originates from Philippines (Ramya et al., 2013). Herb is widely grown in tropical climate of Indonesia, Malaysia, China, Singapore and Brazil, preferably under partial shade conditions. In India, it is grown in the coastal parts of South India, West Bengal, Assam, Karnataka, Madhya Pradesh, and the coastal areas of Gujarat. Indonesia leads in the production of patchouli and meets the majority of the world's demand. Patchouli's distinct earthy and musky fragrance cannot be replicated synthetically, which makes it more valuable globally. Patchouli, primarily cultivated for its essential oil, is in high demand in the aromatic industry due to its earthy and musky aroma, which adds significant value. It’s worth is not only restricted to fragrance but also in pharmaceuticals, food, cosmetics etc. Oil is obtained by steam distillation of the shade dried leaves. The oil has long lasting quality of aroma making it the best fixative. Woody, earthy, and camphoraceous notes makes it distinct. The present study was conducted from 2022 to 2024 at the Department of Plantation, Spices, Medicinal, and Aromatic Crops, College of Agriculture, Vellanikkara, Kerala Agricultural University, Thrissur, to evaluate the effects of chitosan on the growth, yield, and essential oil quality of patchouli. Chitosan was applied as a foliar spray at concentrations of 0.50, 1.00, 1.50, and 2.00 g L-1, administered every two months. The first application was given two months after planting, followed by a total of four sprays throughout the crop growth period. Morphological observations were recorded at various growth stages (60, 120, 180, and 270 days after planting) to assess key traits such as plant height, number of leaves, leaf dimensions (length and width), number of primary and secondary branches, plant spread (north-south and east-west), and stem thickness. Physiological and biochemical analyses were conducted at harvest. Yield parameters, including fresh and dry herb yield per plant and per square metre, were measured at the time of harvest. Essential oil content was extracted from the dried herb, and its composition was analysed using GC-MS profiling. The study revealed that foliar application of chitosan at a concentration of 1.50 g L-1 (T6) resulted in the highest values for most of the morphological traits at 180 days after planting, including plant height (103.95 cm), number of leaves per plant (382.00), leaf length (9.88 cm), leaf width (9.19 cm), number of secondary branches per plant (43.91), total dry matter production (209.73 g plant-1), and leaf-to-stem ratio (1.42). Meanwhile, chitosan application at 2.00 g L-1 (T7) achieved the greatest plant spread in the east-west direction (97.36 cm). A concentration of 0.50 g L-1 chitosan (T4) resulted in the highest number of primary branches per plant (23.66) and stem thickness (14.00 mm), while 1.00 g L-1 (T5) recorded the maximum plant spread in the north-south direction (87.26 cm) at 180 days after planting. In the ratoon crop, foliar application of chitosan at 1.50 g L-1 (T6) produced the highest values for most of the morphological parameters, including the number of primary (26.88) and secondary branches per plant (27.94), plant spread in the north south (70.22 cm) and east-west directions (59.92 cm), and stem thickness (14.33 mm). Chitosan at 0.50 g L-1 (T4) resulted in the tallest plants (70.58 cm), the highest number of leaves per plant (70.33), and the longest leaves (8.86 cm). A concentration of 1.00 g L-1 (T5) achieved the greatest leaf width (8.09 cm), while 2.00 g L-1 recorded the highest dry matter production (128.33 g plant-1). Application of chitosan at a concentration of 1.50 g L-1 (T6) exhibited superior outcomes across several physiological and biochemical parameters. This treatment achieved the highest chlorophyll content (2.68 mg g-1 DW), leaf area (42.83 cm2), leaf area index (4.81), sugar content (36.83 mg g-1 DW), catalase activity (166.32 µg H₂O₂ g-1 min-1), and peroxidase activity (3.35 µmole GC min-1 FW-1). In contrast, the highest carotenoid content (0.69 mg g⁻¹ DW) was observed with a chitosan concentration of 2.00 g L-1 (T7). Notably, lipid peroxidation peaked in the absolute control (T1) and water spray treatments (T2), with values reaching 0.042 Mmole g-1 DW. Additionally, maximum superoxide dismutase activity (1.01) was recorded for chitosan concentration of 1.00 and 2.00 g L-1 (T5 and T7). Application of chitosan at a concentration of 1.50 g L-1 (T6) resulted in the highest fresh (0.76 kg) and dry herb yield per plant (119.06 g), fresh herb yield per m² (5.70 kg), and oil content (20.00 mg g-1 DW). For dry herb yield per m2, however, the highest value (1.22 kg) was observed with a chitosan concentration of 0.50 g L-1 (T4). In addition, 1.50 g L-1 (T6) maintained superior performance in fresh herb ratoon yield (0.66 kg) and dry herb ratoon yield (111.86 g) per plant. Notably, for fresh herb ratoon yield per m² (3.26 kg) and dry herb ratoon yield per m² (0.53 kg), significant improvements were recorded with chitosan at 1.00 g L-1 (T5). The study revealed significant variations in major nutrient uptake among chitosan concentrations. Foliar application of chitosan at 1.50 g L-1 (T6) resulted in the highest nitrogen content (3.83%). In contrast, phosphorus content remained relatively consistent across all the concentrations, with no notable variations. Potassium levels, however, exhibited considerable differences, with the highest concentration (1.38%) observed in T7 (chitosan at 2.00 g L-1). GC-MS analysis of patchouli essential oil revealed notable variations in chemical composition across treatments. Patchouli alcohol was the dominant compound in treatments including T1 (absolute control), T2 (water spray), T3 (acetic acid spray 0.25%), T5 (chitosan 1.00 g L-1), and T7 (chitosan 2.00 g L-1), with the highest concentration recorded in T1 (29.81 %). Additionally, key compounds such as azulene, α-Guaiene, seychellene, and 1H-3a,7-Methanoazulene were identified. Interestingly, azulene was the predominant compound in T4 (chitosan 0.50 g L-1) and T6 (chitosan 1.50 g L-1), with T4 exhibiting the highest concentration of 22.43 per cent. Principal Component Analysis (PCA) performed on 16 morphological and yield traits identified two principal components with eigen value exceeding 1, explaining 89.59 per cent of the total variance. Similarly, PCA of 10 biochemical traits revealed two principal components with eigen value greater than 1, accounting for 86.93 per cent of the total variance. Analysis of 10 essential oil compounds through PCA also identified two principal components with eigen value exceeding 1, explaining 79.88 per cent of the total variance. The study highlighted the positive impact of foliar application of chitosan on the growth, yield, and essential oil production of patchouli. Among the treatments, chitosan at a concentration of 1.50 g L-1 (T6) proved to be the most effective, significantly improving morphological traits, antioxidant enzyme activity, and essential oil yield. However, no notable improvement in essential oil quality was observed, with control treatments outperforming others in this regard. These findings underscore the complexity of chitosan's role as a biostimulant, particularly in influencing secondary metabolite production, which appears to be highly dependent on concentration, application timing, and the molecular form of chitosan. Future studies should focus on optimizing chitosan application by exploring varied concentrations, frequencies, and formulations to enhance essential oil quality of patchouli. Besides, studies combining chitosan with other biostimulants that could improve the relative concentration of key compounds like patchouli alcohol and azulene are recommended. Long-term investigations to assess chitosan's effects on pest and disease resistance under diverse environmental conditions would also provide valuable insights for sustainable patchouli cultivation.