Soil constraints with distinctive coralloid nodulation and nitrogen fixation of “Mecca” alfalfa
Title:
Soil constraints with distinctive coralloid nodulation and nitrogen fixation of “Mecca” alfalfa
Author:
Lynd, J. Q. Ansman, T. R.
Appeared in:
Journal of plant nutrition
Paging:
Volume 13 (1990) nr. 1 pages 77-94
Year:
1990-01
Contents:
The evolutionary origin center of alfalfa within the extensive subhumid Transcaucasia has been a valuable source of Medicago spp. for development of improved alfalfa cultivars. Centuries of natural outcrossing within the perennial, allogamous Medicago species complex resulted in numerous polymorphic plants with desirable genetic characteristics adaptive to harsh climatic and soil environs. Characteristic large coralioid noduiation of M. media (M. falcata X M. sativa) provides means for improved symbiotic nitrogen fixation. The compositae, “Mecca”, (M. sativa spp. falcata Arcemgeli) was selected for desirable noduiation and nitrogen fixation attributes. The objective of this study was to determine soil fertility factors governing its nodulation, nodule histology and cytosol enzymology essential for symbiotic nitrogen fixation. Adequate available soil P was a first limiting factor. Growth, noduiation and nitrogen fixation resulted in significant response to increases in K and Ca only with P combinations. Multiple regression for nodule cytosol plant nutrient composition was nitrogenase activity = 7.78 μg P + 2.73 μg K + 3.53 μg Ca - 6.06 μg Na, R2 = 0.74, C.V. = 12.7%. Distinctive coralloid nodule histology include abundant nondeterminate, apical nodule peripheral meristem regions with numerous developing anastomosic vasculars and transition cells with polyploid nuclei. Cytosol transaminase enzymology of the interstitial nonrhizobial infected cells was significantly increased for increased K levels with adequate P. Interrelationships for these nodule cytosol enzyme activity levels with multiple regression analysis was nitrogenase activity levels = 0.79 IU) Aspartate transaminase (AST) + 1.77 IU Glutamine synthetase (GS) + 0.85 IU Glutamate dehydrogenase (GDH) + 0.38 IU Glutamine-2 oxoglutarate aminotransferase (GOGAT), R2 = 0.63, C.V. = 16.8%. Favorable response to K fertilization has practical economic relevance for increased nodulation and nitrogenase activity levels with improved production of the very important forage legume alfalfa.
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