Stronger ability to absorb nitrate and associated transporters in the invasive plant Xanthium strumarium compared with its native congener

Differences and related physiological mechanisms in effects of ammonium on the invasive plant Xanthium strumarium and its native congener X. sibiricum

“…Nitrogen is one of the key factors affecting plant growth, development and yield ( Lea and Azevedo, 2006 ; Feng et al., 2009 ). A large number of studies have shown that atmospheric nitrogen deposition and soil nitrogen increase can promote invasions of exotic plants ( Lei et al., 2012 ; Sun et al., 2021 ; Luo et al., 2022 ). Ammonium (NH 4 + ) and nitrate (NO 3 - ) are two main nitrogen forms for plants ( Wang et al., 2009 ), and the main soil nitrogen form (Its content is higher than those of other nitrogen forms) are different in different environments.…”

“…Ammonium (NH 4 + ) and nitrate (NO 3 - ) are two main nitrogen forms for plants ( Wang et al., 2009 ), and the main soil nitrogen form (Its content is higher than those of other nitrogen forms) are different in different environments. Nitrate is often the main form of soil nitrogen in disturbed habitats with severe damage from invasive plants ( Sun et al., 2021 ; Luo et al., 2022 ). In general, ammonium nitrogen concentration in soil solution varies over several orders of magnitude (0.1-10 mmol L -1 ; Miller et al., 2007 ), and soil nitrate nitrogen content is 10-1000 times higher than that of ammonium nitrogen ( Cawas and Robert, 2006 ).…”

“…Therefore, the difference in response to soil nitrogen forms between invasive and co-occurring native plants may affect exotic plant invasion and their habitat selection. However, there are few related references, and the existing studies mainly focus on the utilization of nitrogen forms without considering the toxic effect of ammonium nitrogen ( Sun, 2017 ; Sun et al., 2021 ; Luo et al., 2022 ).…”

“…In many ecosystems, most plants prefer to absorb nitrate, and the increase in soil nitrate content is conducive to plant growth and exotic plant invasions ( Alboresi et al., 2005 ; Wang et al., 2012 ; Luo et al., 2022 ). However, after absorbed by plants, nitrate has to be reduced into ammonium for further use by plants.…”

“…Thus, the absorption and assimilation processes of nitrate by plants are more complex than those of ammonium, and it is more favorable for plants to use ammonium as their main nitrogen source from the perspective of energy consumption ( Li and Tong, 2007 ). Some plants indeed prefer ammonium nitrogen and grow better under ammonium relative to nitrite ( Chen et al., 2015 ; Luo et al., 2022 ). However, most plants are sensitive to ammonium, and high ammonium concentration can produce toxic effects, mainly manifested as leaf chlorosis; decreased leaf area; stubby root system; decreased root to shoot ratio, biomass and net photosynthetic rate, etc.…”