摘要:
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.%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.