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 |
Conclusions | 29 |
Symplasmic Transport in Tissues with 8 Figures | 35 |
Copyright | |
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abscisic acid absorption accumulation acid active alga anions apoplasmic ARISZ Australian auxin barley barley roots Biochem Biol Biophys Ca2+ cations CCCP cell wall Chap chloride chloroplasts cytoplasm effect efflux electron Elodea endodermis energy enzyme epidermal strips EPSTEIN excised Exptl external solution exudate fixation Golgi Golgi apparatus growth guard cells higher plants HIGINBOTHAM hormones HSIAO increase influx inhibition inhibitors ion fluxes ion transport ion uptake JESCHKE kinetics kinetin LÄUCHLI leaves light Limonium LÜTTGE maize maize roots mechanism membrane metabolism nectar nitrogen nitrogen fixation nodules nutrient osmotic PALLAGHY permeability phloem phosphate photophosphorylation photosynthesis physiology PITMAN plant cells Plant Physiol plasmalemma plasmodesmata potassium potential protein respiration salt gland SCHNEPF secretion seedlings shoot species stele STEVENINCK stimulation stomatal stomatal opening studies sugar symplasm synthesis tissue tonoplast translocation transpiration transport in plants vacuole Vallisneria vesicles Vicia Vicia faba xylem µmol