Sink-Source Transition in Tobacco Leaves
{'Code': '08070400', 'Directorate': {'LongName': 'Direct For Biological Sciences'}, 'Division': {'LongName': 'Div Of Molecular and Cellular Bioscience'}}
{'SignBlockName': 'Kamal Shukla'}
Leaves of higher plants are converted from sinks to sources                     of photoassimilate as they mature.  This lab has shown that                     termination of photoassimilate import (end of the sink phase)                   in tobacco is coincident with, but not due to, achievement of                   positive carbon balance.  This suggests that phloem unloading                   is symplastic (through plasmodesmata) and ceases when                           plasmodesmatal connections to surrounding cells are either                      lost or blocked.  Interruption of symplastic flow would also                    allow the cells of the phloem to achieve the high solute                        content needed for export by preventing leakage.  Prior                         results support the hypothesis that unloading is passive and                    symplastic.  Additional experiments will be conducted to                        further substantiate the symplastic phloem unloading route in                   tobacco sink leaves by testing the effects of breaking                          plasmodesmatal connections, preventing symplastic transport                     with high pH and inhibitor treatments, and refining the                         present morphometric analysis of the unloading pathway to                       allow stimulation of transport using data on solute flux.                       High resolution EM studies will be conducted to determine                       whether plasmodesmata along the unloading pathway become                        physically obstructed.  Phloem loading will also be studied                     to determine whether an apoplastic step is involved.%%%                                                                                                         These studies on the physiology and structure of a developing                   leaf are providing information on how sugars made during                        photosynthesis are first stored in leaves and then mobilized                    to form grains and fruits.  This has obvious implications for                   a better understanding of crop productivity.  It is                             surprising how much plant structure remains to be elucidated.                   This project is filling an important information gap in plant                   biology.***//
{'FirstName': 'Robert', 'LastName': 'Turgeon', 'EmailAddress': 'ert2@cornell.edu', 'StartDate': '09/01/1988', 'EndDate': None, 'RoleCode': 'Principal Investigator'}
{'Name': 'Cornell University', 'CityName': 'Ithaca', 'ZipCode': '148502820', 'PhoneNumber': '6072555014', 'StreetAddress': '373 Pine Tree Road', 'CountryName': 'United States', 'StateName': 'New York', 'StateCode': 'NY'}
{'Code': '1144', 'Text': 'Molecular Biophysics'}
{'url': 'https://www.nsf.gov/awardsearch/download?DownloadFileName=1988&All=true', 'xml': '8803837.xml'}