caa a22 4500 477101631 CHVBK 20180405111543.0 cr unu---uuuuu 170330e19960701xx s 000 0 eng 10.1007/BF00195735 doi (NATIONALLICENCE)springer-10.1007/BF00195735 Secondary plasmodesmata formation in the minor-vein phloem of Cucumis melo L. and Cucurbita pepo L [Elektronische Daten] [Gayle Volk, Robert Turgeon, Dwight Beebe] Numerous branched plasmodesmata (pd) are present between bundle-sheath cells (BSCs) and specialized companion cells known as intermediary cells (ICs) in the minor-vein phloem of melon (Cucumis melo L.) and squash (Cucurbita pepo L.). These pd were found to be secondary, i.e., they form across existing walls. Sink, sink-source transition, and source tissues were sampled from developing and mature leaves. In sink tissue, IC precursors divide to produce the two to four ICs and associated sieve elements which are present by the time of the sink-source transition. Plasmodesmata along the interface between the IC precursor and adjacent BSCs in sink tissue are unbranched and few in number. Before the leaf tissue undergoes the sink-source transition, the number of pd channels (individual branches of pd) becomes more numerous. This increase in number of pd channels occurs at least in part and perhaps entirely by branching, resulting in more channels on the IC-side than on the BSC-side. In melon there is a 12-fold increase in the number of pd channels within the IC-side of the interface and a corresponding 9-fold increase in pd channels within the BSC-side. Thus, secondary pd form by the time of the sink-source transition and may be involved in phloem loading and photoassimilate export. The system described is well-defined and amenable to experimental manipulation: secondary pd form in large numbers, at a particular interface, over a short period of time, and in a highly predictable manner. Springer-Verlag, 1996 Cucumis nationallicence Cucurbita nationallicence Intermediary cell nationallicence Phloem nationallicence Plasmodesmata nationallicence Sink-source transition nationallicence BSC : bundle-sheath cell nationallicence DAP : days after planting nationallicence IC : intermediary cell nationallicence LPI : leaf plastochron index nationallicence pd : plasmodesmata nationallicence PI : plastochron interval nationallicence Volk Gayle Section of Plant Biology, Cornell University, 14853, Ithaca, NY, USA aut Turgeon Robert Section of Plant Biology, Cornell University, 14853, Ithaca, NY, USA aut Beebe Dwight Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 Rue Sherbrooke Est, H1X 2B2, Montréal, Québec, Canada aut Planta Springer-Verlag 199/3(1996-07-01), 425-432 0032-0935 199:3<425 1996 199 425 https://doi.org/10.1007/BF00195735 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00195735 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Volk Gayle Section of Plant Biology, Cornell University, 14853, Ithaca, NY, USA aut NATIONALLICENCE 700 1- Turgeon Robert Section of Plant Biology, Cornell University, 14853, Ithaca, NY, USA aut NATIONALLICENCE 700 1- Beebe Dwight Institut de Recherche en Biologie Végétale, Université de Montréal, 4101 Rue Sherbrooke Est, H1X 2B2, Montréal, Québec, Canada aut NATIONALLICENCE 773 0- Planta Springer-Verlag 199/3(1996-07-01), 425-432 0032-0935 199:3<425 1996 199 425 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer