The Tracing Of Pathway For Carbohydrate By CFDA In Neolamarckia Cadamba

Phloem is responsible for transporting assimilation products from plant photosynthesis.The transport and distribution of photoassimilate are major factors determining the plant yield and quality,in which the phloem plays a crucial role.Photoassimilate is the product of photosynthetic CO₂ fixation,and its transport includes three processes:phloem unloading in source,long-distance phloem transport and phloem loading in sink.The transport of photoassimilate in phloem has two transport mechanisms:symplast pathway and apoplastic pathway.Carboxylfluorescein?CF?is a"membrane impermeable"probe,which is an ideal tracer for symplast.CF could be loaded by weak acid or ester form?CFDA?,and the long-distance transport regulation could be speculated through the distribution of CFDA fluorescence in plant.In this study,we traced the pathway of carbohydrate by CFDA in N.cadamba.The main research results are as follows:1.Petiole were treated with CFDA solution under different time intervals.Under the effect of atmospheric pressure,1 h was required for CFDA permeating into cortex parenchyma cells via cotton thread.Then,4 h was required for CF transfer to phloeming from cortex parenchyma cells.The transport rate of CF in cortex parenchyma cells and in phloem were approximately 0.17 cmh^-1 and 3 cmh^-1,respectively.2.Horizontal transport was recognized between phloem and xylem in N.cadamba.After 5 h treating with CFDA,CF was loaded from cortex parenchyma to sieve element-companion cell,then spread into phloem parenchyma cells through plasmodesmata and this process ended with CF transfer into the pith from xylem pith parenchyma cells.3.Symplastic isolation was absent in phloem and surrounding parenchyma cells,and symplast pathway was found during the phloem unloading?via plasmodesmata?.CF transfered into sieve from cortex parenchyma cells,then the fluorescence spread to the surrounding parenchyma cells after long-distance transport in phloem.