Abstract
Four maize hybrids, two with high and two with low levels of postanthesis nitrate reductase activity were grown under field conditions. The characteristic enzyme patterns had been established in previous work. Nitrate reductase and proteases were measured in three representative leaves (ear leaf, fourth leaf above and fourth leaf below the ear) at intervals throughout the period of grain development. Concurrent with enzyme sampling, other plants were harvested and subdivided into top, middle and lower leaves, husks, stalks, and ear. Dry weights, nitrate, and reduced N were determined on all plant parts for each sampling. These data established the rate of N accumulation by the grain and depletion from the vegetative material and provide some insight into the relation between newly reduced and remobilized N and accumulation of grain N. Other plants were harvested at maturity for yield and harvest indices for dry weight and N.
Nitrate reductase activity was higher in comparable leaves from the high than from the low nitrate reductase genotypes throughout the grain development period. There was no mathematical correlation between nitrate reductase activity and nitrate content of the leaves or stalks, however the high nitrate reductase genotypes maintained a higher amount of nitrate per plant (largely in the stalk) during the later stages of grain development. From the patterns of plant nitrate content it was deduced that the low nitrate reductase genotypes terminated nitrate absorption sooner than the high nitrate reductase types. Proteolytic activities (casein as substrate at pH 5.5 and 7.5) were higher and increased earlier in the low than in the high nitrate reductase genotypes. The “low nitrate reductase-high protease” genotypes had a higher percentage of grain N, and higher harvest index for N than did the “high nitrate reductase-low protease” genotypes. These results permit the tentative conclusions that: (a) redistribution of vegetative N accounted for more of the grain N in the low than in the high nitrate reductase genotypes; and (b) leaf protease activities are more closely related to the accumulation of grain N than leaf nitrate reductase activity.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Beevers L., Hageman R. H. The role of light in nitrate metabolism in higher plants. Photophysiology. 1972;(7):85–113. [PubMed] [Google Scholar]
- Brunetti N., Hageman R. H. Comparison of in Vivo and in Vitro Assays of Nitrate Reductase in Wheat (Triticum aestivum L.) Seedlings. Plant Physiol. 1976 Oct;58(4):583–587. doi: 10.1104/pp.58.4.583. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Feller U. K., Soong T. S., Hageman R. H. Leaf Proteolytic Activities and Senescence during Grain Development of Field-grown Corn (Zea mays L.). Plant Physiol. 1977 Feb;59(2):290–294. doi: 10.1104/pp.59.2.290. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hay R. E., Earley E. B., Deturk E. E. Concentration and Translocation of Nitrogen Compounds in the Corn Plant (Zea Mays) During Grain Development. Plant Physiol. 1953 Oct;28(4):606–621. doi: 10.1104/pp.28.4.606. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Martin C., Thimann K. V. Role of Protein Synthesis in the Senescence of Leaves: II. The Influence of Amino Acids on Senescence. Plant Physiol. 1972 Oct;50(4):432–437. doi: 10.1104/pp.50.4.432. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Martin C., Thimann K. V. The role of protein synthesis in the senescence of leaves: I. The formation of protease. Plant Physiol. 1972 Jan;49(1):64–71. doi: 10.1104/pp.49.1.64. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Neyra C. A., Hageman R. H. Relationships between Carbon Dioxide, Malate, and Nitrate Accumulation and Reduction in Corn (Zea mays L.) Seedlings. Plant Physiol. 1976 Dec;58(6):726–730. doi: 10.1104/pp.58.6.726. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Perez C. M., Cagampang G. B., Esmama B. V., Monserrate R. U., Juliano B. O. Protein metabolism in leaves and developing grains of rices differing in grain protein content. Plant Physiol. 1973 Mar;51(3):537–542. doi: 10.1104/pp.51.3.537. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Shaner D. L., Boyer J. S. Nitrate Reductase Activity in Maize (Zea mays L.) Leaves: I. Regulation by Nitrate Flux. Plant Physiol. 1976 Oct;58(4):499–504. doi: 10.1104/pp.58.4.499. [DOI] [PMC free article] [PubMed] [Google Scholar]