Semiochemicals and Lipid Laboratory, Department of Life Sciences, Presidency University, Kolkata, 700073, India.
Department of Environmental Studies, Jadavpur University, Kolkata, 700032, India.
J Plant Res. 2024 May;137(3):463-484. doi: 10.1007/s10265-024-01527-2. Epub 2024 Feb 9.
Floral biochemistry and stress physiology is an underexplored aspect of mangroves, which should be investigated as part of preservation and restoration efforts. A thriving true mangrove tree (Bruguiera gymnorrhiza (L.) Lamk.) and a threatened mangrove-associate species (Heritiera fomes Buch. Ham.) were studied in the Sundarban region of India for seasonal variations in floral odours, non-volatile phytochemicals, antioxidant enzyme activities, and surface water chemistry in surrounding habitat. Both species were found to exhibit significant differences in floral volatilomes, protein contents, antioxidant enzyme activities, total flavonoids, and total phenolic contents between spring and autumn blooms. The bird-pollinated flowers of B. gymnorrhiza also showed considerable seasonal differences in floral anthocyanin and proline contents, indicating vulnerability of the post-anthesis open flowers to environmental factors. Contrarily to previous findings, B. gymnorrhiza floral bouquet appeared to be enriched in various classes of volatiles - dominated by sulphurous compounds in bud stage and terpenoids in open stage. Floral anthocyanins, contributing to the striking colouration of the calyx, were found to comprise cyanidin and delphinidin derivatives. Other glycosides of cyanidin and delphinidin were detected in H. fomes flowers, contributing to visual guides to potential food rewards for pollinating insects. Floral tissue in H. fomes was found to be protected by densely overlapping layers of stellate trichomes containing sesquiterpenoids as phytoprotectants. Comparison of the two floral species suggested that H. fomes flowering is optimized to oligohaline (but not freshwater) vernal conditions; whereas B. gymnorrhiza blooms are adapted for biologically enriched (including abundant herbivores and microbial growth), mesohaline forest habitats.
红树林的花学生物化学和应激生理学是一个尚未被充分探索的领域，应该作为保护和恢复工作的一部分进行研究。本研究以印度孙德尔本斯地区的真红树林（Bruguiera gymnorrhiza (L.) Lamk.）和受威胁的红树林伴生种（Heritiera fomes Buch. Ham.）为研究对象，探讨了其在季节性花香、非挥发性植物化学物质、抗氧化酶活性以及周围生境地表水化学方面的变化。结果表明，两个物种在春季和秋季开花期间，其花朵挥发物、蛋白质含量、抗氧化酶活性、总类黄酮和总酚含量存在显著差异。具有鸟类传粉的 B. gymnorrhiza 花朵在花期中也表现出花色苷和脯氨酸含量的季节性差异，这表明花朵在授粉后开放期间对环境因素较为敏感。与之前的发现相反，B. gymnorrhiza 的花香似乎富含各种挥发性物质——在花蕾期以含硫化合物为主，在开放期以萜烯类化合物为主。花色苷是花萼鲜艳颜色的主要贡献者，被发现包含矢车菊素和飞燕草素衍生物。在 H. fomes 的花朵中还检测到矢车菊素和飞燕草素的其他糖苷，这有助于为传粉昆虫提供潜在食物奖励的视觉指南。H. fomes 的花朵组织被含有倍半萜类化合物的星状毛状体的紧密重叠层所保护，这些化合物具有植物保护作用。对这两个花种的比较表明，H. fomes 的开花时间优化适应于寡盐（而非淡水）春季条件；而 B. gymnorrhiza 的开花时间则适应于富含生物的（包括丰富的食草动物和微生物生长）、中盐森林生境。
