Wang Chuan-Hua, Wang Ming, Jia Rao-Zhen, Guo Hua
Hubei International Scientific and Technological Cooperation Center of Ecological Protection and Management in the Three Gorges Area, China Three Gorges University, Yichang, China.
Engineering Research Center of Eco-environment in the Three Gorges Reservoir Region, Ministry of Education, China Three Gorges University, Yichang, China.
Front Plant Sci. 2018 May 8;9:568. doi: 10.3389/fpls.2018.00568. eCollection 2018.
In this study, effects of nitrogen (N) availability on growth, survival of var. , 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 var. 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⋅y. When the N deposition increased from 8.59 kg N⋅ha⋅y to 14.24, 20.49, 32.99 and 57.99 kg N⋅ha⋅y, 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⋅y) to 10.7% of 50.0 kg N⋅ha⋅y, when they were treated with 0.00, 6.25, 12.5, 25.0, and 50.0 kg N⋅ha⋅y 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 var. treated with higher nitrogen deposition. Compared with slightly effects of NRA, GSA of var. 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 var. , 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.
在本研究中，评估了氮（N）有效性对[具体品种]生长、存活的影响，以及它是否以综合生理方式响应氮胁迫。通过田间试验测定了[具体品种]的藻体生长和繁殖体存活情况、藻体氮和磷（P）含量以及磷酸单酯酶（PME）活性。在一系列室内试验中还研究了其对氨和硝酸盐的差异吸附、谷氨酰胺合成酶（GSA）和硝酸还原酶（NRA）的活性。结果表明，氮沉降显著降低了这种地衣的生长和存活，氮敏感性阈值建议为6.0 kg N·ha·y。当氮沉降从8.59 kg N·ha·y增加到14.24、20.49、32.99和57.99 kg N·ha·y时，地衣藻体的生长速率分别下降了26.47%、39.01%、52.18%和60.3%；而当地衣繁殖体分别用0.00、6.25、12.5、25.0和50.0 kg N·ha·y的氮沉降处理时，其存活率从对照（0.0 kg N·ha·y）的92.8%下降到50.0 kg N·ha·y时的10.7%。与铵态氮的充分吸附相比，当藻体浸没在低于0.4 mM的溶液中时，未发生硝酸盐吸附。我们的结果还表明，藻体总氮、N:P比随氮有效性增加而增加，PME活性与藻体总氮显著相关。这些都表明，当[具体品种]受到较高氮沉降处理时发生了磷限制。与NRA的轻微影响相比，[具体品种]的GSA对氮有效性有显著响应；此外，GSA和NRA与藻体生长速率和繁殖体存活显著负相关。这些结果表明，氮胁迫确实会降低[具体品种]的生长和存活，地衣会受到过量氮的综合影响，而非零散影响，包括氮的吸收、同化，甚至氮和磷的养分平衡。
