Springer Online Journal Archives 1860-2000
Summary Diffusion coefficients for FITC-molecular probes in intercellular pores (D) and rate of molecular probe loss into the vacuole (k1) have been obtained for FITC molecular probes in staminal hairs ofSetcreasea purpurea. The kinetic curves of FITC-Gly, -Ala, -Leu,-Ser, -Thr, -Cys, -Met, -Tyr, -Asp, -Glu, -Asn, -Gln, -Lys, -His,-Arg, -(Asp)2, -(Glu)2, -(Lys)2, -(Asp)3, -(Glu)3, -(Gln)2, -(Gln)3, -(Gln)4, and carboxyfluorescein (group I probes) matched the curves calculated for simple diffusion through a chain of cells, while the majority of kinetic curves of FITC-Phe, and -Try (group II probes) did not. None of the kinetic curves for FITC-(Met)2 and -(His)2 (group III probes) matched. Average Ds for group I probes ranged from 0.77× 10−8cm2/s to 3.75× 10−8cm2/s and for group II probes were 0.50× 10−8cm2/s. A meaningful average D for group III probes could not be calculated. Average k1 for group I probes ranged from 1.62× 10−7/μm2/s to 13.21× 10−7/μm2/s, and for group II probes were 5.42 and 11.54× 10−7/μm2/s. Average k1s for group III probes could not be calculated. Symplastic transport occurred by cell-to-cell diffusion for most of the probes (e.g., group I probes) but not always for some (e.g., group II probes) and never for others (group III probes). The rate of cell-to-cell diffusion and loss within the vacuole depended upon the molecule's specific structure, molecular weight and charge. We concluded that plasmodesmata select for molecules that are hydrophilic, small and have a charge of from — 2 to — 4, and against molecules that contain either Phe, Try, Met or His groups.
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