CARBON ISOTOPIC DISCRIMINATION IN PEPPER SEEDLINGS AS AFFECTED BY NITROGEN LEVEL AND SOURCE

The impacts of increasing nitrogen (N) supply and various N sources (NO₃– vs.
NH₄⁺ and organic-N vs. inorganic-N) on plant growth and the natural abundance of ¹³C (δ¹³C) were studied in pepper (Capsicum annuum L. ‘Quito’) seedlings grown in 1 L pots filled with peat in a growth chamber.
In a first experiment, plants were irrigated at four different N levels (0, 1, 3 and 7 mM NO₃^–). In a second experiment, treatment consisted of three different NO₃^–/NH₄⁺ ratios (100/0, 50/50 and 0/100) at a constant N concentration of 3 mM. In a third experiment, plants were irrigated with different organic-N/inorganic-N ratios (100/0, 98/2, 96/4, 92/8 and 88/12) by using NO₃^– as inorganic N source, and a liquid fertilizer derived from sheep manure (LSM) as organic N source.
Increasing N levels (applied as NO₃^–) significantly increased plant growth and plant N concentration.
At the highest N level, the C/N ratio increased, which, together with the increase in the δ¹³C values, indicates a decrease in stomatal conductance.
On the other hand, the N form (NO₃^– vs.
NH₄⁺) significantly affected growth and carbon isotope composition.
NO₃^–-grown plants showed the lowest δ¹³C values, which can be attributed to the fact that these plants presented higher leaf stomatal conductance than NH₄⁺-grown plants.
Finally, changes in growth and carbon discrimination in plants grown under combined organic and inorganic fertilization were related with the plant response to NO₃^– application and osmotic stress following liquid manure application.

XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Environmental, Edaphic, and Genetic Factors Affecting Plants, Seeds and Turfgrass

P. Flores, P. Hellín, J. Fenoll, P.J. Murray

natural abundance, ¹³C, stable isotope, nitrate, ammonium

https://doi.org/10.17660/ActaHortic.2012.938.35