埃格草(Egeria densa)对铵氮胁迫的生长和生理响应

为了解富营养水体中NH₄+-N胁迫对埃格草（Egeria densa）的影响，通过室外模拟试验，研究了埃格草在不同ρ（NH₄+-N）（0、0.5、2.0 mg/L）下的RGR（relative growth rate，相对生长率）、R/S（root/shoot ratio，根冠比）、w（SC）（SC为可溶性糖，soluble sugar）、w（淀粉）、w（蔗糖）、w（FAA）（FAA为游离氨基酸，free amino acid）、w（NH₄+-N）和w（NO₃--N）的变化.结果表明:随着外源ρ（NH₄+-N）的增加，埃格草的RGR和R/S呈降低的趋势，并且在ρ（NH₄+-N）为2.0 mg/L时显著降低（RGR为P < 0.001，R/S为P < 0.05）；埃格草中w（SC）和w（淀粉）在ρ（NH₄+-N）为0.5和2.0 mg/L下有不同程度显著降低[w（SC）为P < 0.01和P < 0.001，w（淀粉）为P < 0.001和P < 0.05]，w（蔗糖）在ρ（NH₄+-N）为2.0 mg/L时显著降低（P < 0.001）；w（FAA）和w（NH₄+-N）有随外源ρ（NH₄+-N）升高而升高的趋势，并且在ρ（NH₄+-N）为2.0 mg/L时升高显著[w（FAA）为P < 0.01，w（NH₄+-N）为P < 0.05]；w（NO₃--N）在ρ（NH₄+-N）为0.5和2.0 mg/L下有不同程度显著降低（P < 0.01和P < 0.001）.相关分析表明，w（SC）、w（淀粉）和w（蔗糖）之间呈显著正相关，三者与w（FAA）和w（NH₄+-N）之间均呈显著负相关，而与w（NO₃--N）呈显著正相关；w（FAA）和w（NH₄+-N）呈显著正相关，而二者与w（NO₃--N）均呈显著负相关.研究显示，NH₄+-N影响埃格草的生长，导致C-N代谢的不平衡. 

Ammonium Nitrogen Stress on the Growth and Physiological Responses of Egeria densa

In order to understand the effects of ammonium nitrogen (NH₄⁺-N) stress on Egeria densa in eutrophic water bodies, morphological and physiological variations such as relative growth rate (RGR), root/shoot ratio (R/S), soluble sugar (SC), starch, sucrose, free amino acid (FAA), NH₄⁺-N, and nitrate nitrogen (NO₃^--N) of E. densa at different external NH₄⁺-N concentrations of 0, 0.5 and 2.0 mg/L were investigated in an outdoor simulation experiment. The results showed that the RGR and R/S ratio of E. densa showed a tendency to decrease with increasing external NH₄⁺-N concentration, but decreased significantly with 2.0 mg/L NH₄⁺-N. The SC andstarch contents decreased significantly with 0.5 and 2.0 mg/L NH₄⁺-N. The sucrose content decreased significantly with 2.0 mg/L NH₄⁺-N. The FAA and NH₄⁺-N contents tended to increase with increasing external NH₄⁺-N concentration, but increased significantly with 2.0 mg/L NH₄⁺-N. The NO₃^--N contents tended to decrease significantly with 0.5 and 2.0 mg/L NH₄⁺-N. The SC, starch, and sucrose contents were positively correlated with each other, but were negatively correlated with FAA and NH₄⁺-N and positively correlated with NO₃^--N. The FAA and NH₄⁺-N were positively correlated with each other, but were negatively correlated with NO₃^--N. Our experimental results showed that external NH₄⁺-N can affect the growth of E. densa and lead to an imbalance in carbon-nitrogen metabolism.