Microcosm Study on Allelopathic Effects of Leaf Litter Leachates and Purified Condensed Tannins from Kandelia obovata on Germination and Growth of Aegiceras corniculatum

Abstract

Kandelia obovata (Ko) and Aegiceras corniculatum (Ac) are common and dominant plant species in mangrove wetlands in South China, which are distributed in similar tidal zones along the coastline. The present study aimed to determine the allelopathic effects of leaf litter leachates (LLLs) from Ko and their purified condensed tannins (PCTs) on the germination and growth of Ac by mangrove microcosms. Replicate pots containing five different levels of LLLs and PCTs were separately prepared and propagules of Ac were placed in each treatment. Both LLLs and PCTs significantly inhibited the germination and growth of Ac, especially at high concentrations. The final germination rates of the roots and stems and the numbers of fine roots declined continuously, while other growth indicators, including the lengths of fine roots and nutritive roots and the biomasses of roots, stems, and leaves first increased and then decreased with increasing levels. These results indicate that LLLs from the leaf litter of Ko, in particular their PCTs, exerted an inhibition effect on propagule germination and seedling growth of Ac, and the inhibitory effects were concentration dependent. This study suggested that condensed tannins from leaf litter, acting as allelochemicals, could regulate the natural regeneration of a mangrove forest.

Allelopathic Potential of Mangroves from the Red River Estuary against the Rice Weed Echinochloa crus-galli and Variation in Their Leaf Metabolome

“…Similarly, Chen and Peng [ 30 ] showed that leaf aqueous extracts of A. marina and B. gymnorhiza inhibited the growth of cabbage (a model species) and K. candel (species following A. marina in mangrove succession). In addition, Lang et al [ 63 ] demonstrated the allelopathic potential of K. obovata against one of its associated species A. corniculatum in a Chinese mangrove, indicating that allelopathy plays a role in mangrove ecosystems.…”

Litter facilitates plant development but restricts seedling establishment during vegetation regeneration

“…On the positive side, litter protects seeds from herbivores (Hu et al, 2016; Nakhoul et al, 2020), enables seed germination by controlling soil temperature fluctuations (Xia et al, 2015), alleviates seed desiccation by shielding the soil surface from ultraviolet light (Visscher et al, 2016) and promotes seed vigour by creating water diffusion barriers for dry grasslands and microclimates for shady forests (Chen, Ma, et al, 2018; Ruprecht et al, 2010). Conversely, litter input can also make certain constraints stronger, such as negatively impacting seeds by placing them in deep shade or darkness (Rotundo & Aguiar, 2005), or by releasing allelochemicals from coniferous (Kainulainen et al, 2003) and broadleaved litter (Lang et al, 2021).…”

“…Conversely, litter input can also make certain constraints stronger, such as negatively impacting seeds by placing them in deep shade or darkness (Rotundo & Aguiar, 2005), or by releasing allelochemicals from coniferous (Kainulainen et al, 2003) and broadleaved litter (Lang et al, 2021).…”

Physiological and Biochemical Responses of Kandelia obovata to Upwelling Stress

“…Kandelia obovata is not only a dominant mangrove species along the south-eastern coast of China but also an important species for mangrove afforestation [35]. As a pioneer species, K. obovata is mainly distributed at low tide and middle tide zones, where it is frequently subjected to upwelling [36,37]. K. obovata can survive in areas with salinity of up to 27.58‰ [38].…”