Phenology and physico -chemical characterization of cinnamon buds.

Abstract

Cinnamon (Cinnamomum verum Presl.) assumes considerable importance among the world's perennial spices, which is extensively used in food and therapeutic applications. The dried inner bark is the primary trade commodity in cinnamon. In addition to the bark, immature fruit buds are also internationally traded as cinnamon tree flowers. However, the phenological stages of cinnamon have not been systematically characterized, and information on the morphological and biochemical changes during bud development remains limited. The present study aims to identify and describe the phenological growth stages of cinnamon using the extended Biologische Bundesanstalt, Bundessortenamt, and Chemische Industrie (BBCH) scale, and to evaluate the morphological and biochemical variations that occur throughout the development of cinnamon buds. The phenological studies, morphological, and biochemical observations of cinnamon buds were conducted on the IISR-Navasree variety, maintained at the Model Nursery for Spices, Department of Plantation, Spices, Medicinal and Aromatic Crops, College of Agriculture, Vellanikkara. Comparative analyses of C. verum, C. malabatrum, and C. cassia were carried out using trees maintained at the Departmental Farm, Department of Plantation, Spices, Medicinal and Aromatic Crops, College of Agriculture, Vellanikkara, and at ICAR-IISR, Kozhikode, respectively. The study was conducted from 2023 to 2025. The present study identified and described eight principal growth stages and 40 secondary growth stages as per the extended BBCH scale. The principal growth stages include three vegetative stages (bud, leaf, and shoot development), one economically significant stage (development of harvestable vegetative plant parts), two flowering stages (inflorescence and flower development), and two fruiting stages (fruit development and maturity). The duration of each principal stage exhibited considerable variation. The complete cinnamon growth cycle required 27,337.95 °C day, with the development of harvestable vegetative plant parts registered the longest duration, followed by shoot development and fruit development. Physico-chemical analyses of cinnamon buds were performed in distinct phenophases, include inflorescence development (517), flowering (615-619), fruit development (710 and 719), and fruit maturity (819). These analyses showed significant variations in morphological, biochemical, and volatile characteristics. Inflorescence positions were predominantly terminal to axillary. The number of flowers per inflorescence remained constant from early to peak flowering stages (517-617), followed by a sharp decline at stage 619. The number of fruits per inflorescence remained consistent throughout fruit development. Floral and fruit size, as well as weight, increased progressively with the advancement of phenophases. Most flowers exhibited six tepals and nine stamens, with three staminodes present in the innermost whorl. At phenophase 615, floral abnormalities were detected, with varied tepal numbers from 4 to 10 in flowers. Biochemical analyses revealed significant developmental changes. Moisture content declined from 72.00 per cent at flowering (615) to 43.06 per cent at fruit maturity (819). Total carbohydrate content increased from 5.46 per cent at early flowering (517) to 14.26 per cent at fruit development (719). Ash content ranged from 5.92 g per 100 g at early flowering (517) to 8.10 g per 100 g during complete fruit development (719). Total phenolic content (TPC) decreased from 419.93 mg GAE g-1 DW (517) to 62.50 mg GAE g-1 DW (819). Coumarin content ranged from 0.01 per cent to 0.05 per cent, with the highest concentration observed in early floral stages (517 and 617). Volatile profiling of cinnamon buds at selected developmental stages exhibited considerable diversity in both composition and relative abundance. Flowering stages (517-617) were enriched in δ-cadinene and caryophyllenyl alcohol. Later, fruiting stages (710-819) were characterized by the dominance of β-caryophyllene and δ- cadinene. Cinnamyl acetate, an important aromatic ester, reached its maximum concentration at 619 (37.52%). Phytochemical profiling of C. verum, C. cassia, C. malabatrum (bark, leaves and buds) and market samples revealed significant interspecific and organ-specific variations in coumarin content and volatile oil composition. Coumarin content exhibited variation among species and plant parts, ranged from 0.02-0.09 per cent (C. verum), 0.02-0.55 per cent (C. cassia), and 0.01-0.03 per cent (C. malabatrum), whereas market samples recorded the highest levels (0.60% in bark). GC-MS profiling revealed significant qualitative and quantitative differences in volatile composition among bark, bud and leaf oils. In C. cassia, (E)-cinnamaldehyde was the major compound in bark (84.03%) and buds (73.99%). Whereas C. verum showed (E)-cinnamyl acetate dominance in buds (68.91%) and leaves (81.30%), with bark rich in (E)- cinnamaldehyde (73.41%) and benzyl benzoate (8.52%). C. malabatrum was characterized by a linalool-rich bark (42.68%) and β-caryophyllene-enriched leaves (32.08%) and buds (9.95%). Market samples exhibited elevated (E)-cinnamaldehyde (91.7%) in bark and sesquiterpenes such as τ-cadinol (17.16%) and δ-cadinene (14.49%) in buds. The detailed description of phenological growth stages based on the BBCH scale, along with information on morphological and biochemical changes identified in this study, will facilitate the scientific cultivation of cinnamon, particularly in the planning and timing of crop production, processing, and protection practices. Further, the developed BBCH scale serves as a valuable tool for crop improvement programs, including the conservation and characterization of germplasm, as well as the assessment of climate change impacts on cinnamon production. Future research should prioritize biochemical profiling of cinnamon buds in other promising varieties and conduct multi- location characterization across diverse agro-ecological zones of Kerala to evaluate environmental influences on bud quality.