Transport in Plants II: Part B Tissues and OrgansU. Lüttge, M.G. Pitman In the first part (Part A) of this volume on transport, there was an emphasis on the processes occurring at the membranes bounding the cells. It was convenient to distinguish active and passive processes of transport across the membranes, and to recognize that certain transport processes may be regulated by internal factors in the cells such as cytoplasmic pH, concentrations of ions, of malate or of sugar in the vacuoles, or the hydrostatic pressure. Cells in tissues and organs show the same kinds of properties as individual cells, but in addition there can be cell to cell transport related to the organization of the tissue. Firstly cells within a tissue are separated from the external solutions by a diffusion path comprising parts of the cell walls and intercellular spaces; more generally this extra-cytoplasmic part of the tissue has been called the apoplasm. A similar term is "free space". Secondly, the anatomy of cells in tissues seems to allow some facilitated, local transport between cells in a symplasm. Entry into the symplast and subsequent transport in a symplasmic continuum seems to be privileged, in that ions may not have to mix with the bulk of the cytoplasm and can pass from cell to cell in particular cytoplasmic structures, plasmodesmata. In Chara plants, this kind of transport is found operating across the multi-cellular nodes as the main means of transport between the long internodal cells. |
Contents
Apoplasmic Transport | 3 |
Particular Cell Systems | 6 |
Conclusions | 29 |
Copyright | |
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accumulation acid activity alga apoplasmic apoplast ARISZ Australian auxin barley barley roots Biochem Biol Biophys Ca2+ cations cell wall Chap chloride chloroplasts coleoptile cortex cuticle cytoplasm effect efflux electron Elodea endodermis enzyme epidermal EPSTEIN excised Exptl external solution exudate gland cells Golgi Golgi apparatus growth guard cells higher plants hormones increase induced influx inhibition inhibitors ion fluxes ion transport ion uptake JESCHKE kinetics kinetin LATIES LÄUCHLI leaf leaves Limonium LÜTTGE maize maize roots mechanism membrane metabolism nectar nitrogen fixation nutrient osmotic PALLAGHY parenchyma pathway permeability phloem phosphate photosynthesis physiology PITMAN plant cells Plant Physiol plasmalemma plasmodesmata potassium potential protein root nodules salt glands SCHNEPF secretion secretory seedlings shoot slices soil species stele STEVENINCK stimulation stomatal stomatal opening structure studies sugar symplasm synthesis tissue tonoplast translocation transport in plants vacuole vesicles Vicia Vicia faba xylem µmol