Macroscopic and microscopic study on floral biology and pollination of Cinnamomum verum Blume (Sri Lankan)

Abstract

Cinnamomum verum Blume (syn Cinnamomum zeylanicum) commonly known as Ceylon cinnamon, has gained worldwide attention and well supported by experimental data. Maintaining the yield quality and quantity are essential, especially for high-end value-added products. Breeding superior varieties and producing good quality planting materials are critical for commercial cultivation efforts. However, limited literature is available on the floral development and biology of C. verum. We assessed the seasonal flowering, floral development and pollination of type A and type B varieties of C. verum. Both macroscopic and microscopic data were collected on floral biology, pollination, male and female floral organs before and after pollination. Cinnamomum verum is morpho-anatomically, structurally, and physiologically adapted for cross-pollination, possible between the two cultivars; type A (Sri Gemunu) and type B (Sri Wijaya) flowers; naturally evolved with Protogynous Dichogamy. It possesses a dry stigma, which changes its surface characteristics after pollination. During close-pollination, a higher percentage of pollen shrink and shrivel on stigma while it develops callose plugs to obstruct the growth of the pollen tube. However, during changes in environmental conditions, female and male stages in the same tree overlap for about 45-60 min suggesting possible close-pollination within the same plant. Moreover, 4-8% of the flowers formed fruits after natural close and hand pollination. pollen was found fully hydrated even after close-pollination. Although C. verum is adapted for cross-pollination, natural close-pollination is also possible. The data suggest the complex nature of the sexual reproduction of C. verum. Well-managed breeding attempts will develop superior C. verum varieties.

Chloroplast genome, nuclear ITS regions, mitogenome regions, and Skmer analysis resolved the genetic relationship among Cinnamomum species in Sri Lanka

“…The current analysis suggests comparatively higher nucleotide diversity in the trn H- psb A and pet A- psb J regions than in the common universal barcoding regions. However, a previous study has also reported inadequacy of the nucleotide diversity in the trn H- psb A region for molecular level identification of the Cinnamomum species in Sri Lanka [ 5 ]. The current work proposes new barcode regions of ycf1 , ITS and mitochondrial genes of atp6 and cox 1 for the identification of Cinnamomum species.…”

“…However, the Scanning Electron Microscopic analysis (SEM) of C . verum (Sri Lanka) pollen samples [ 5 ] suggests considerable differences compared to recently published SEM data of C . verum (India) [ 99 ].…”

“…While the name C. zeylanicum [97] has widely been used in the literature for Sri Lankan Cinnamon, it is considered a synonym for C. verum [98]. However, the Scanning Electron Microscopic analysis (SEM) of C. verum (Sri Lanka) pollen samples [5] suggests considerable differences compared to recently published SEM data of C. verum (India) [99]. The pollen size and the spine length are different between them.…”

“…Cinnamomum species are macromorphologically characterized by buds perulate or not, leaves alternate or opposite, pinnately veined or tripliveined, domatia presence in axil of lateral veins and floral characters such as inflorescences paniculate with cymes bearing strictly opposite lateral flowers. Recent characterization efforts include leaf epidermal micromorphology, having a reticulate periclinal wall or non-reticulate periclinal wall and pollen morphology [ 4 , 5 ].…”

“…The morphology of some species drastically changes when they are grown or cultivated under other agroecological conditions [ 13 , 14 ]. In addition, the natural cross-pollination behavior [ 5 , 15 ] of Cinnamomum has created considerable intraspecies diversity [ 16 ], reflected by both morphological and biochemical traits [ 17 ]. Therefore, morphology based identification of Cinnamomum species is challenging [ 3 , 18 – 20 ].…”