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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Nitrate reductase activity and spad readings in leaf tissues of guinea grass submitted to nitrogen and potassium rates

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Author(s):
Lavres Junior, Jose [1] ; Gomes dos Santos, Jr., Joao de Deus [2] ; Monteiro, Francisco Antonio [3]
Total Authors: 3
Affiliation:
[1] Univ Sao Paulo, Lab Plant Nutr, Ctr Nucl Energy Agr CENA, BR-13400970 Piracicaba, SP - Brazil
[2] Embrapa Cerrados, BR-73310970 Planaltina, DF - Brazil
[3] ESALQ USP, Dept Soil Sci, Luiz de Queiroz Coll Agr, BR-13418900 Piracicaba, SP - Brazil
Total Affiliations: 3
Document type: Journal article
Source: Revista Brasileira de Ciência do Solo; v. 34, n. 3, p. 801-809, MAY-JUN 2010.
Web of Science Citations: 12
Abstract

Nitrogen and K deficiency are among the most yield limiting factors in Brazilian pastures. The lack of these nutrients can hamper the chlorophyll biosynthesis and N content in plant tissues. A greenhouse experiment was carried out to evaluate the relationship among N and K concentrations, the indirect determination of chlorophyll content (SPAD readings), nitrate reductase activity (RNO3-) in newly expanded leaf lamina (NL) and the dry matter yield for plant tops of Mombaça grass (Panicum maximum Jacq.). A fractionated 5² factorial design was used, with 13 combinations of N and K rates in the nutrient solution. The experimental units were arranged in a randomized block design, with four replications. Plants were harvested twice. The first harvest occurred 36 days after seedling transplanting and the second 29 days after the first. Significance occurred for the interaction between the N and K rates to SPAD readings and to RNO3- assessment taken on the NL during the first growth. Besides, RNO3- and SPAD readings increased only with the NL N concentration, reaching the highest values of both variables up to about 25 g kg-1, but were ratively constant at higher leaf N. Significant relationships either between SPAD readings or RNO3- activity and shoot dry mass weight were also observed. The critical levels of N concentration in the NL were, respectively, 22 and 17g kg-1 in the first and second harvest. Thus, SPAD instrument and RNO3- assessment can be used as complementary tools to evaluate the N status in forage grass. (AU)