chapter 8-3 nutrient relations: nitrogen - Bryophyte Ecology ...

18 Chapter 8-3: Nutrient Relations: Nitrogen
found that four of these amino acids induced branching,
relative to the controls, but no branching appeared in any of
the methionine treatments (Figure 4).
Figure 4. Effects of water soluble amino acids on number of
branches in the Java moss, Taxiphyllum barbieri. cont = control,
gly = glycine, meth = methionine, ser = serine, arg = arginine,
ala = alanine. From Alghamdi (2003).
Figure 5. Effect of water soluble amino acids on the
biomass, length, and robustness (wt:length) of the Java moss,
Taxiphyllum barbieri. Cont = control, Gly = glycine, Meth =
methionine, Ser = serine, Arg = arginine, Ala = alanine. Length
and biomass represent sum of 3 stems; n = 10 sets of 3 stems.
Notation as in Figure 2. Based on Alghamdi (2003).
Methionine proved to be inhibitory to growth in
length whereas serine caused an increase in both dry
biomass and length relative to controls (Figure 5; Alghamdi
2003). Arginine as the only N source at 1, 10, and 30
mg/L caused a striking increase in the biomass and ratio of
dry biomass to length, but maintained a length somewhat
less than that of the N-free controls (Figure 5). This
resulted in unusually short, wide plants, combined with
high protein concentrations but below normal chlorophyll
concentrations at the lowest level applied (1 mg/L; Figure
6).
Methionine likewise caused an increase in biomass
and decrease in length growth with concentration increase
(1, 10, 30 mg/L). Alanine caused an increase in both
length and biomass with concentration, with the overall
effect being one of a more robust plant at higher
concentrations, having a higher biomass to length ratio than
that of the controls. The mosses responded to 1 mg/L
glycine much as they did to the N-free medium, but at
higher concentrations (20 and 30 mg/L) their length and
biomass both increased considerably over that of controls.
Figure 6. Effect of water soluble amino acids on the protein
content and total chlorophyll concentration of the Java moss,
Taxiphyllum barbieri. cont = control, gly = glycine, meth =
methionine, ser = serine, arg = arginine, ala = alanine. n = 10 sets
of 3 stems. Notation as in Figure 2. From Alghamdi (2003).
Alghamdi (2003) then compared the effects of glycine,
which seemed to produce the "healthiest" plants, to those of
the inorganic forms of N. This aquatic moss did less well
on the inorganic forms NH4NO3 or NO3 - than on NH4 +
alone or NH4 + + the amino acid glycine and did best on
glycine alone, producing more biomass, longer stems, and
more branches (Figure 7, Figure 8). In fact, glycine
seemed to induce branching (Table 1).
In the same series of experiments, Alghamdi (2003)
examined the effects of inorganic N and glycine on the
chlorophyll and protein content. Glycine, both alone and in
combination with NH4 + , resulted in the highest protein
concentrations (Figure 9). The effects on chlorophyll were
less clear, but the highest total chlorophyll occurred in the
highest glycine concentration. NH4 + at 20 mg/L, however,
produced similar chlorophyll concentrations, but at 30
mg/L the chlorophyll content decreased.