Growth, morphology and flooding tolerance of transgenic alfalfa (Medicago sativa L.) expressing varying levels of a class 1 barley (Hordeum vulgare) hemoglobin

Although hemoglobins are universally present in the plant kingdom, the exact physiological function(s) of these enigmatic proteins has yet to be elucidated. Recent biochemical and physiological studies have indicated that class 1 non-symbiotic hemoglobins modulate plant nitric oxide (NO) levels. At this same time NO research in plants is intensive due to the discovery of its participation as a signal molecule in various environmental and hormonal stimuli.; Extending previous research from maize cell and alfalfa root culture systems, we sought to determine the influence of class 1 hemoglobin over- and under-expression on the growth, morphology and flooding tolerance of whole alfalfa plants. Hemoglobin levels were determined in control alfalfa plants in addition to plants transformed to over-express or under-express a class 1 non-symbiotic barley hemoglobin gene. Alfalfa plants that over-express the hemoglobin gene (Hb+) were found to have early vigorous growth, strong apical dominance of both root and shoot systems, and accelerated development relative to controls or plants underexpressing the Hb gene (Hb-). (Abstract shortened by UMI.)...