Radial oxygen loss is correlated with nitrogen nutrition in mangroves

Abstract

The present study aimed to explore the possible functions of radial oxygen loss (ROL) on mangrove nutrition. A field survey was conducted to explore the relations among ROL, root anatomy and leaf N in different mangrove species along a continuous tidal gradient. Three mangroves with different ROL (Avicennia marina > Kandelia obovata > Rhizophora stylosa) were then selected to further explore the dynamics of N at root-soil interface. The results showed that seaward pioneer mangrove species such as A. marina appeared to exhibit higher leaf N despite growing under worse nutrient conditions. Greater leaf N in pioneer mangroves coincided with their special root structure (e.g., high porosity together with a thin lignified/suberized exodermis) and powerful ROL. An interesting positive relation was observed between ROL and leaf N in mangroves. Moreover, the data from rhizo-box further showed that soil nitrification was also strongly correlated with ROL. A. marina, which represented the highest ROL among the three mangrove species studied, consistently possessed the highest NO3−, nitrification and ammonia-oxidizing bacteria and archaea (AOB and AOA) gene copies in the rhizosphere. Besides, both NO3− and NH4+ influxes were found to be higher in the roots of A. marina when compared to those of K. obovata and R. stylosa. In summary, greater N acquisition by pioneer mangroves such as A. marina was strongly correlated with ROL which would regulate N transformation and translocation at root-soil interface. The implications of this study may be significant in mangrove nutrition and the mechanisms involved in mangrove zonation.

Comparative study on anatomical traits and gas exchange responses due to belowground hypoxic stress and thermal stress in three tropical seagrasses

“…The presence of air lacunae implies that the middle cortex of seagrass rhizome may act as belowground oxygen storage ( Pedersen et al, 1998 ; Borum et al, 2005 ; Sand-Jensen et al, 2005 ). Similar observations were reported in the seagrasses C. rotundata and H. ovalis ( Roberts, McComb & Kuo, 1985 ; Pedersen et al, 1998 ; Connell, Colmer & Walker, 1999 ; Kuo & den Hartog, 2006 ) and in other wetland plants ( Cheng et al, 2020a ; Armstrong et al, 2000 ; Soukup, Votrubová & Čížková, 2002 ; Matthews & Seymour, 2014 ). It has been suggested that tissue porosity is associated with tolerance to hypoxic conditions ( Visser et al, 2000 ; Hasler-Sheetal et al, 2015 ; Cheng et al, 2020a ).…”

“…These anatomical characteristics are tightly coupled to fundamental physiological functions of plants, such as cellular respiration and photosynthesis. Their roles in mediating plant stress tolerance have been extensively explored in many plant species ( Jensen et al, 2005 ; Pi et al, 2009 ; Jovanovic et al, 2015 ; Dai et al, 2017 ; Cheng et al, 2020a , 2020b ; de Lopes et al, 2020 ; Mei et al, 2020 ; Scholz et al, 2021 ). Studies in mangrove plants suggest that differences in both porosity and ROL barrier contribute to different sensitivity to waterlogging, root zone hypoxia, nutrient limitation and heavy metal stress ( Pi et al, 2009 ; Dai et al, 2017 ; Cheng et al, 2020a , 2020b ; Pedersen et al, 2021 ).…”

“…Their roles in mediating plant stress tolerance have been extensively explored in many plant species ( Jensen et al, 2005 ; Pi et al, 2009 ; Jovanovic et al, 2015 ; Dai et al, 2017 ; Cheng et al, 2020a , 2020b ; de Lopes et al, 2020 ; Mei et al, 2020 ; Scholz et al, 2021 ). Studies in mangrove plants suggest that differences in both porosity and ROL barrier contribute to different sensitivity to waterlogging, root zone hypoxia, nutrient limitation and heavy metal stress ( Pi et al, 2009 ; Dai et al, 2017 ; Cheng et al, 2020a , 2020b ; Pedersen et al, 2021 ). In-depth studies of the rhizosphere environments in seagrasses thus far have focused on temperate species, such as Zostera marina , Z. muelleri, Ruppia maritima and Posidonia australis ( Brodersen et al, 2015a , 2015b , 2016 , 2017a , 2018a , 2018b ; Martin et al, 2019 ).…”

Characteristics of Microbial Community and Function With the Succession of Mangroves

“…Although mangrove sediments are rich in organic matter, they are generally nutrient-deficient. Nutrient limitations were also widely reported in mangrove forests (Feller et al, 2003;Reef et al, 2010;Wang and Gu, 2013;Cheng et al, 2020). Even worse, anaerobic conditions might further aggravate the enrichment of anaerobic microbes and reductive phytotoxins (e.g., CH 4 , H 2 S, and sulfides).…”

“…The adaptation and succession of mangroves in intertidal regions are speculated to be closely related to microbes in the sediments. Unfortunately, the potential roles of microbes and their functions in mangrove ecosystems are still poorly understood, although changes in vegetation during mangrove succession and how mangrove plants adapt to intertidal environmental adversities have been well studied ( Wang et al, 2019 ; Cheng et al, 2020 ).…”