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The difference in N metabolism between NAD(P)H-specific NR-deficient mutant and wild-type barley (Hordeum vulgare L.)

Author:
Abdel-Latif, Salwa A., Abou-Zeid, Hanan M.
Source:
Journal of plant nutrition 2019 v.42 no.17 pp. 2029-2042
ISSN:
1532-4087
Subject:
Hordeum vulgare, NAD (coenzyme), barley, genotype, metabolism, mutants, nitrate reductase, nitrate reduction, nitrates, nitrites, nitrogen, nutrient solutions, phloem, photophase, roots, seedlings, shoots, stable isotopes, xylem
Abstract:
Barley (Hordeum vulgare L.) is an important crop for cereal research. In this study, two barley genotypes the wild-type (Steptoe) and the mutant (Az12) were used. An experiment was conducted using ¹⁵N-tracing method to NADH-specific nitrate reductase (NR)-deficient mutant seedling of barley. The N-depleted seedlings were exposed to a nutrient solution containing nitrate and nitrite, and were labeled with ¹⁵N for 38 h under (14 L/10D) cycles. The two genotypes utilized ¹⁵NO₃⁻ and accumulated it as reduced ¹⁵N, predominately in the shoots. However, nitrate reduction in the Az12 shoots was 9% lower than that in the Steptoe shoots at 38 h. As a result, in the Az12, nitrate accumulation in shoots was 78% higher than that in the Steptoe. Accumulation of reduced ¹⁵N in the Az12 roots was nearly similar to that of the Steptoe roots, but 8% lower in the Az12 shoots than in the Steptoe shoots at the end of the experiment. Also for both genotypes, root contribution increased during L/D cycles and decreased during the subsequent light cycle. Upward transport of reduced ¹⁵N via the xylem in the Az12 was nearly two times higher than that in Steptoe during the second light period (24–38 h). In both genotypes, xylem transport of reduced ¹⁵N was far exceeded the downward phloem transport. AbbreviationsAnlaccumulation of reduced ¹⁵N from ¹⁵NO₃⁻ in non-labeled roots of split roots Araccumulation in roots of reduced ¹⁵N from ¹⁵NO₃⁻ Asaccumulation in shoots of reduced ¹⁵N from ¹⁵NO₃⁻ Rr¹⁵NO₃⁻ reduction in roots Rs¹⁵NO₃⁻ reduction in shoots Tptranslocation to root of shoot reduced ¹⁵N from ¹⁵NO₃⁻ in phloem Txtranslocation to shoot of root-reduced ¹⁵N from ¹⁵NO₃⁻ in xylem FWfresh weight
Agid:
6606413