Biochemical basis for differential leaf senescence of two maize hybrids
Ho, InSun
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Permalink
https://hdl.handle.net/2142/19709
Description
Title
Biochemical basis for differential leaf senescence of two maize hybrids
Author(s)
Ho, InSun
Issue Date
1989
Doctoral Committee Chair(s)
Below, Frederick E.
Department of Study
Crop Sciences
Discipline
Crop Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Agronomy
Biology, Plant Physiology
Language
eng
Abstract
Senescence, the deteriorative process that ultimately leads to the death of an organism, was examined by ear removal treatment on two maize hybrids (B73 x Mo17 and Farm Service brand 854) which are known to have different rates of natural- and ear-removal-induced leaf senescence. Changes in activities and relative amounts of PEPCase and RuBPCase (by SDS-PAGE and Western Blot), soluble protein, Chl, specific leaf weight, percent moisture, carbohydrate, reduced N, and P in the selected leaves of these hybrids were determined. In general, the selected leaves of both hybrids irrespective of ear treatment underwent senescence as judged by decline in most, if not all, of the constituents. In addition, the onset of decline in activities of PEPCase and RuBPCase, reduced N, and soluble protein was not altered by ear removal in both hybrids. These results suggest that, the ear itself does not initiate the senescence process in maize. However, ear removal did alter the rate of leaf senescence, especially for B73 x Mo17. As judged by an accelerated decline in the leaf chemical and enzymic constituents, ear removal accelerated leaf senescence rate for B73 x Mo17 while it had limited effect on the senescence rate for FS854. Ear removal appears to accentuate the inherent leaf senescence rate of maize hybrids and therefore, this treatment maybe useful in identifying the plants with late-season health and with high production potential. Activities and Western blot analysis of carboxylases showed that the slow senescing trait observed in FS854 plants is highly associated with the retention of activities as well as the amount of carboxylating enzymes. This association was most notable for PEPCase relative to RuBPCase. On the other hand, ear removal appears to affect only the amount of carboxylases as its effect on activities was not evident until the final stages of the experiment. The preferential loss in activities and amount of PEPCase relative to RuBPCase suggests that PEPCase, in mature leaves, may be the major source of N in developing maize kernels.
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