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No description available.

The occurrence of the cotton root rot fungus, Phymatotrichum omnivorum (Shear) Duggar, in sharply defined, localized areas in certain fields led to the suggestion that there may be a specific soil chemical factor which limits the spread of the fungus. The available sodium, potassium, calcium, and magnesium contents of infested and adjacent noninfested soils in 13 fields were determined and compared. At seven sites, there were no significant differences in cation contents of infested and adjacent noninfested areas (p = 0.05). Available sodium levels were higher in infested areas at three sites, and higher in noninfested areas at three sites. Potassium and calcium levels were higher in the infested area at one site, and higher in the noninfested areas at two sites. Magnesium levels were higher in the noninfested areas at three sites. Contrary to previous reports, the fungus was found to cause severe disease in soils with available sodium contents as high as 4.2 milliequivalents per 100 g soil. Applications of sodium chloride at rates ranging from 1800 to 4000 kg/ha did not reduce disease severity or increase yield significantly in ten field trials.

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This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

During Arabidopsis embryogenesis, cell-cell signaling plays an essential role in establishing an organized body plan centered around two major axes of development: apical-basal and radial. Two topics of great interest are how the layered structure is initiated and maintained during and after embryogenesis and how communication between layers is achieved to allow for coordinated development. Recent research involving Receptor-Like Kinases (RLKs) in plants suggests that their roles in integrating various signals are important in many aspects of development, including embryonic and post-embryonic patterning. The research presented here describes the roles of two pairs of RLKs with independent roles in two different signaling environments. The first RLK pair, GSO1 and GSO2, function in root development at the transition to photoautotrophic nutrition to integrate sugar signals and regulate root growth. GSO1 and GSO2 regulate root epidermal cell identity by controlling the pattern of cell division of stem cells. The second pair of RLKs, RPK1 and TOAD2, function to control root development by regulation of meristem proliferation and a coordinated response to signaling molecules of the CLE family. The response of wild-type roots to treatment with CLE peptides (A-type) is meristem growth arrest, resulting in short roots. toad2 mutants are insensitive to the effect of CLE peptides in reducing meristem size and TOAD2 also regulates RPK1 upon CLE stimulation. Although responding to different signals, the two pairs of RLK share a common output of regulating cell proliferation in and around the root meristem, especially in the epidermis of the root.

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No description available.