AUTHOR=Wang Chuan-Hua , Wang Ming , Jia Rao-Zhen , Guo Hua 

TITLE=Thalli Growth, Propagule Survival, and Integrated Physiological Response to Nitrogen Stress of Ramalina calicaris var. japonica in Shennongjia Mountain (China)

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.00568

DOI=10.3389/fpls.2018.00568

ISSN=1664-462X

ABSTRACT=<p>In this study, effects of nitrogen (N) availability on growth, survival of <italic>Ramalina calicaris</italic> var. <italic>japonica</italic>, and whether it respond nitrogen stress in an integrated physiological way was evaluated. Thalli growth and propagule survival, thalli N and phosphorus (P) content, and activity of phosphomonoesterase (PME) of <italic>R. calicaris</italic> var. <italic>japonica</italic> were determined in a field experiment. Its differentiate adsorption in ammonia and nitrate, the activity of glutamine synthetase (GSA) and nitrate reductase (NRA) also were investigated in a series of indoor experiments. The results showed that N deposition significantly decreased the growth and survival of this lichen, and the N sensitivity threshold was suggested at 6.0 kg N⋅ha<sup>-1</sup>⋅y<sup>-1</sup>. When the N deposition increased from 8.59 kg N⋅ha<sup>-1</sup>⋅y<sup>-1</sup> to 14.24, 20.49, 32.99 and 57.99 kg N⋅ha<sup>-1</sup>⋅y<sup>-1</sup>, the growth rates of lichen thalli decreased by 26.47, 39.01, 52.18 and 60.3%, respectively; Whereas the survival rate of the lichen propagules decreased from 92.8% of control (0.0 kg N⋅ha<sup>-1</sup>⋅y<sup>-1</sup>) to 10.7% of 50.0 kg N⋅ha<sup>-1</sup>⋅y<sup>-1</sup>, when they were treated with 0.00, 6.25, 12.5, 25.0, and 50.0 kg N⋅ha<sup>-1</sup>⋅y<sup>-1</sup> deposition. Compared with an adequate adsorption of ammonium N, no nitrate adsorption occurred when thalli was submerged in solution lower than 0.4 mM. Our results also suggested that thalli total nitrogen, N:P ratio increased with N availability, and the activity of PME was significantly correlated with thalli total nitrogen. These all indicated that phosphorus limitation occurred when <italic>R. calicaris</italic> var. <italic>japonica</italic> treated with higher nitrogen deposition. Compared with slightly effects of NRA, GSA of <italic>R. calicaris</italic> var. <italic>japonica</italic> responded nitrogen availability significantly; In addition, GSA and NRA negatively correlated with thalli growth rate and propagule survival significantly. These results indicated that nitrogen stress do decrease growth and survival of <italic>R. calicaris</italic> var. <italic>japonica</italic>, and lichen would be impacted by excess nitrogen in a integrated, not a fragmentary way, including nitrogen uptake, assimilation, even nutrient balance of nitrogen and phosphorous.</p>