Effects of Nitrogen Forms on the Growth and Nitrogen Accumulation in Buchloe dactyloides Seedlings

Abstract

Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] has become the most widely cultivated warm-season turfgrass in northern China because of its low-maintenance requirements. Nitrogen (N) can be applied to plants in a range of formulations. However, preference of nitrogen uptake and the effects of N form on plant growth and nitrogen accumulation has not been established in buffalograss. In this study, we evaluated the effects of different inorganic nitrogen forms (NO₃^--N, NH₄⁺-N, and NO₃^--N: NH₄⁺-N = 1:1) on growth and nitrogen accumulation in buffalograss seedlings. Results showed that supply of three N forms significantly increased buffalograss seedlings growth, biomass, and N contents of all plant organs compared with the seedlings receiving free nitrogen. Plants achieved better growth performance when they received nitrate as the sole N source, which stimulated stolon growth and increased the biomass of ramets, spacers, and aboveground and total plant biomass, and also allocated more biomass to ramets and more N to spacers. Meanwhile, those plants supplied with the treatment +NH₄NO₃ displayed a significantly greater N content in the ramet, ¹⁵N abundance, and ¹⁵N accumulation amount in all organs. These data suggest NO₃^--N supplied either singly or in mixture increased vegetative propagation and thus facilitates buffalograss establishment. However, applications of ammonium caused detrimental effects on buffalograss seedlings growth, but +NO₃^- could alleviate NH₄⁺-induced morphological disorders. Thus, recommendations to increase vegetative propagation and biomass accumulation in buffalograss seedlings should consider increasing NO₃^--N in a fertility program and avoiding applications of nitrogen as NH₄⁺-N.

Keywords: 15N; Buchloe dactyloides; biomass allocation; nitrogen allocation; nitrogen forms.

Figure 1

Box plot of growth characters of buffalograss seedlings, as affected by nitrate, ammonium, and ammonium nitrate. Each value is the mean ± SD (n = 10). The values not sharing the same letters are significantly different at p < 0.05 according to Duncan’s test of one-way ANOVA. CK, -NH₄NO₃; N1, +NO₃⁻; N2, +NH₄⁺; N3, +NH₄NO₃. Box plots indicate interquartile range in the box area, median (solid line in the box), mean (solid circle in the box) 25% and 75% percentiles (lower and upper box margins), 10% and 90% percentiles (lower and upper error bars), and outliers (solid rhombus outside the error bars). Note: (A): plant height of buffalograss seedlings in different nitrogen forms. (B): stolon number of buffalograss seedlings in different nitrogen forms. (C): tiller number of buffalograss seedlings in different nitrogen forms. (D): stolon length of buffalograss seedlings in different nitrogen forms. (E): pitch number of stolon of buffalograss seedlings in different nitrogen forms. (F): spacer length of buffalograss seedlings in different nitrogen forms. (G): root surface of buffalograss seedlings in different nitrogen forms. (H): root average diameterof buffalograss seedlings in different nitrogen forms. (I): root total length of buffalograss seedlings in different nitrogen forms.

Figure 2

The influence of nitrogen form on biomass and biomass allocation of buffalograss seedlings. Each value is the mean ± SD (n = 6). CK, -NH₄NO₃; N1, +NO₃⁻; N2, +NH₄⁺; N3, +NH₄NO₃. Box plots indicate interquartile range in the box area, median (solid line in the box), mean (solid circle in the box) 25% and 75% percentiles (lower and upper box margins), 10% and 90% percentiles (lower and upper error bars), and outliers (solid rhombus outside the error bars). Note: (A): root biomass of buffalograss seedlings in different nitrogen forms. (B): spacer biomass of buffalograss seedlings in different nitrogen forms. (C): ramet biomass of buffalograss seedlings in different nitrogen forms. (D): orter biomass of buffalograss seedlings in different nitrogen forms. (E): total biomass of stolon of buffalograss seedlings in different nitrogen forms. (F): biomass allocation of buffalograss seedlings in different nitrogen forms. Different lowercase letters indicate a significant difference among different nitrogen forms (p < 0.05), values designated by different capital letters indicate significant difference of total biomass among nitrogen forms.

Figure 3

The influence of nitrogen form on N contents and N allocation of buffalograss seedlings. Each value is the mean ± SD (n = 5). CK, -NH₄NO₃; N1, +NO₃⁻; N2, +NH₄⁺; N3, +NH₄NO₃. The lowercase letters indicate significant difference at the 0.05 level among different treatments of the same organ; the capital letters indicate significant difference at the 0.05 level among different organs under a given treatment. Note: (A): nitrogen contents of different buffalograss seedlings organs in different nitrogen forms. (B): nitrogen allocation of different organs of buffalograss seedlings in different nitrogen forms. Different lowercase letters indicate a significant difference among different nitrogen forms (p < 0.05), Values designated by different capital letters indicate significant difference among organs.

Figure 4

Schematic diagram of Buchloe dactyloide.