Effects of varying the proportions of NO3— and NH4+ in the growth medium on seedling growth and tomato fruit yield (Lycopersicon esculentum L. cv. Trust F1) were investigated in greenhouse hydroponic experiments. The presence of NH4+ as the sole N source (11 mM) was toxic: it curtailed growth and decreased chlorophyll content of the leaves. However, at low concentration (10 % of total N), the presence of NH4+, with or without added dissolved inorganic carbon (DIC), increased vegetative growth and fruit yield by ˜ 15 %, and enhanced taste/flavor of the fruits. In DIC‐enriched treatment, pH was maintained at 5.8 by addition of KHCO3 or as CaCO3. The presence of NH4+, at 10 % of total N, inhibited NO3— uptake rates by ˜ 27 %. The rates of uptake of NO3— and NH4+ were comparable (13.3 and 14.2 mmol plant—1 d—1, respectively, in the presence of DIC, and 14.7 and 14.0 mmol plant—1 d—1, respectively, in the absence of DIC), despite such a large difference in their concentrations in the nutrient feed solution. A higher proportion of NH4+ (up to 50 % of total N) had no further significant effect upon early vegetative growth, but in a long‐term experiment resulted in a high incidence of blossom end‐rot (BER) disease, thereby severely curtailing fruit yield. The presence of even 1.1 mM NH4+ reduced Ca2+ and Mg2+ accumulation in the leaves as well as in fruits. 相似文献
本试验旨在探明绵羊感染16型蓝舌病病毒(Bluetongue virus type 16,BTV16)后细胞因子IFN-γ、IL-2、IL-4和IL-10的消长特点。用实时荧光定量PCR检测方法对感染BTV16后3只绵羊上述4种因子mRNA进行检测,同时设立阴性对照绵羊,并以0 d mRNA为基准,计算mRNA的相对表达量,同时检测病毒抗体效价、测量绵羊体温。结果显示,接种BTV16的3只绵羊均不同程度产生抗体和体温症状,4种细胞因子的mRNA在接种病毒2~4 d内均出现显著上升,其中IFN-γ峰值在2.58~27.84倍之间,IL-2峰值在5.24~17.19倍之间,IL-4峰值在2.16~3.43倍之间,IL-10峰值在15.78~48.77倍之间,个体上升幅度存在显著差异,4种细胞因子均在高水平持续6 d左右后逐渐下降。对照绵羊上述参数在正常范围内波动。本研究阐明了接种BTV16后绵羊细胞因子IFN-γ、IL-2、IL-4、IL-10在转录水平上的消长特点,为进一步深入开展BTV感染特征、宿主机体免疫机制研究提供参考。 相似文献