Poster: Hormones
Abs #
581: Cytokinin effects on nitrate reductase, nitrite reductase, and glutamine synthetase activity in nitrogen deficient bean (Phaseolus vulgaris).
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Presenter: |
Hansberry, Janis , hansberry@ccmail.nevada.edu |
Authors | Hansberry, Janis (A) Neuman, Dawn (A) Nagel, Alissa (A) | | Affiliations: |
(A): University of Nevada, Las Vegas
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Nutrient availability, specifically nitrogen, has been a major limitation to growth and reproductive success throughout plant evolution. Nitrogen availability can alter leaf form and structure; with stressed leaves ultimately reaching smaller sizes or senescing altogether. Leaf senescence or chlorosis is a productive form of aging leading to tissue death. As senescence progresses, production of constitutive hydrolytic enzymes exploits the degradation of large, complex molecules into smaller subunits (e.g., amino acids, nucleotides, sugars, and fatty acids). These "expensive" materials are subsequently “recycled” and transported to regions of more active growth, to areas of storage for future growth, or to seeds for future development of the ensuing generation.
Cytokinins are plant growth regulators comprised of a number of structurally diverse and biologically versatile compounds whose mechanism of action remains largely unknown. This class of N6-substituted adenine derivatives has been shown to participate in the regulation of several plant processes including cell division, mobilization of nutrients, and leaf senescence. Application of cytokinins to chlorotic leaves stimulates a transposition to green tissue, a result known as the “green island effect”. This green island effect may occur through an influx of nitrogen to the region.
Previously, we have reported on cytokinin effects on nitrate reductase (NR) and nitrite reductase (NiR) activities, the first two enzymes in the nitrogen metabolism pathway. Preliminary results suggest that NR and NiR exhibit dose dependent responses to applied cytokinins. In this current study, we include data on the third enzyme in the pathway, glutamine synthetase, and on chlorophyll analysis in ”nitrogen starved” Phaseolus.
