A Model for the Development of the Rhizobial and Arbuscular Mycorrhizal Symbioses in Legumes and Its Use to Understand the Roles of Ethylene in the Establishment of these two Symbioses

We propose a model depicting the development of nodulation and arbuscular mycorrhizae. Both processes are dissected into many steps, using Pisum sativum L. nodulation mutants as a guideline. For nodulation, we distinguish two main developmental programs, one epidermal and one cortical. Whereas Nod factors alone affect the cortical program, bacteria are required to trigger the epidermal events. We propose that the two programs of the rhizobial symbiosis evolved separately and that, over time, they came to function together. The distinction between these two programs does not exist for arbuscular mycorrhizae development despite events occurring in both root tissues. Mutations that affect both symbioses are restricted to the epidermal program. We propose here sites of action and potential roles for ethylene during the formation of the two symbioses with a specific hypothesis for nodule organogenesis. Assuming the epidermis does not make ethylene, the microsymbionts probably first encounter a regulatory level of ethylene at the epidermis–outermost cortical cell layer interface. Depending on the hormone concentrations there, infection will either progress or be blocked. In the former case, ethylene affects the cortex cytoskeleton, allowing reorganization that facilitates infection; in the latter case, ethylene acts on several enzymes that interfere with infection thread growth, causing it to abort. Throughout this review, the difficulty of generalizing the roles of ethylene is emphasized and numerous examples are given to demonstrate the diversity that exists in plants

Advances in agricultural microbiology

xxii, 704 hlm. : ill.; 24 cm

Mikroorganisme tanah dan pertumbuhan tanaman, ed.2/ Rao

xii, 352 hal.: ill.; 24 cm

Mikroorganisme tanah dan pertumbuhan tanaman, ed.2/ Rao

xii, 352 hal.: ill.; 24 cm

Mikroorganisme tanah dan pertumbuhan tanaman, ed.2/ Rao

xii, 352 hal.: ill.; 24 cm

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Not AvailableWe conducted an incubation study for a period of 74 days to assess the sole and combined effect of CaCl2 and CaSO4 on wheat straw amended soil carbon mineralisation. Application of salts either alone or in combination significantly reduced the cumulative carbon mineralisation. Residue carbon mineralisation was significantly affected due to interactive effect of CaCl2 and CaSO4 throughout the incubation period. Application of chloride salt has a more depressing effect on residue carbon mineralisation than the sulphate. The study clearly demonstrated that cumulative carbon mineralisation in soil was positively correlated with dehydrogenase activity (r=0.53, P=0.01), water soluble carbon (r=0.46, P=0.05), soil pH (r=0.87, P=0.01) and negatively correlated with soil electrical conductivity (r=-0.81, P=0.01). The results suggest that C mineralisation affected by both CaCl2 and CaSO4 either alone or in combination by influencing soil osmotic properties and dehydrogenase activity. The study indicates that saline soils offer an opportunity to sequester C because decomposition of added wheat straw was more strongly decreased under higher EC value.Not Availabl

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file:///C:/Users/NS%20Raju/Downloads/Algorithmsforweather-basedmanagementdecisionsinmajor.pdfCrop weather calendars (CWC) serve as tools for taking crop management decisions. However, CWCs are not dynamic, as they were prepared by assuming normal sowing dates and fixed occurrence as well as duration of phenological stages of rainfed crops. Sowing dates fluctuate due to variability in monsoon onset and phenology varies according to crop duration and stresses encountered. Realizing the disadvantages of CWC for issuing accurate agromet advisories, a protocol of dynamic crop weather calendar (DCWC) was developed by All India Coordinated Research Project on Agrometeorology (AICRPAM). The DCWC intends to automatize agromet advisories using prevailing and forecasted weather. Different modules of DCWC, namely, Sowing & irrigation schedules, crop contingency plans, phenophase-wise crop advisory, and advisory for harvest were prepared using long-term data of ten crops at nine centers of AICRPAM in eight states in India. Modules for predicting sowing dates and phenology were validated for principal crops and varieties at selected locations. The predicted sowing dates of 10 crops pooled over nine centers showed close relationships with observed values (r2 of .93). Predicted phenology showed better agreement with observed in all crops except cotton (Gossypium L.; at Parbhani) and pigeon pea [Cajanus cajan (L.) Millsp.] (at Bangalore). Predicted crop phenology using forecasted and realized weather by DCWC are close to each other, but number of irrigations differed, and it failed for accurate prediction in groundnut at Anantapur in drought year (2014). The DCWCs require further validation for making it operational to issue agromet advisories in all 732 districts of IndiaNot Availabl