Plant architecture of <i>Paspalum vaginatum</i> schwartz modified by nitrate and ammonium nutrition
Paspalum vaginatum Schwartz plants were grown under greenhouse conditions in a continuous-flow hydroponic culture, containing NO-3 or NH+4 or NH4NO3 as nitrogen source. After 30 days, the size of aerial biomass and root system decreased significantly when plants were supplied with NH+4 as exclusive nitrogen source. Compared to NO-3 treatment, reducing and non-reducing sugars were decreasing together with a significant increase in amino acids content. NH+4-nutrition caused tillers to grow toward an orthogravitropic position (average angle of 68° with respect to the horizontal), and with NO-3-nutrition, tillers tended to become diagravitropic (average angle of 23°). With NH4NO3 all the parameters measured had values in between those of the other two sources. Thus, the morphologic differences among plants growing in NO-3 or NH+4 nutrition confirm the hypothesis that nitrogen source determines the growth habit of tillers in P. vaginatum by modulating the endogenous levels of reducing-non-reducing sugars.