Transport in Plants
-Over small distances substances move by difusion and cytoplasmic steaming.
-Long distance transport is called translocation -Organic substances move-Multidirectional -Inorganic substances and water Unidirectional -Diffusion passive, random slow and not dependent on living system -Gaseous exchange-is due to diffusion -Diffusion rate depends on concentration gradient, permebility, temperature and pressure -FACILITATED DIFFUSION -----Carried outfor those substances having hydrophilic moiety gradient required, carrier mediated ,without energy -water channels made up of aquaporins -ACTIVE TRANSPORT ----Uphill tranport, energy & carrier proteins both required -Common fetures to facilitated and Active transport----saturation ,selectively , Inhibition Hormonr regulation -Water potenial ----difference of Kinetic energy -Solute potential----loss of freeenrgy due to addition of solutes -Pressure potentialchange in free energy due to external pressure -Tonoplast and plasma membrane are two important determinants of movememt of molecules in or out of the cell -Net direction and rate of osmosis depends on both pressure gradient and concentartion gradient -During plasmolysis water lost first from cytoplasm and then from vacuole -Imbibition depends on diffusion, water potential gradient & affinity between adsorbant and liquid -Bulk flow can be achieved either through positive hydrostatic pressure gradient or negative hydrostatic pressure gradient -Xylem water , minerals and organic nitrogen , hormones
-Symplastic path -- Systems of interconnected protoplasts -Root pressure --positive hydrostatic pressure, leads to guttation, mosdest push in overall water transport , greatest contribution- reestablishments of continuity of water column -Cell wall of guard cells show radial arrangement of microfibrils -Cohesion,adhesions and surface tension are three physical properties of water which provide tensile strength and capillarity -Evolutions of C4 photosynthetic path isfor maximising CO2 utilisation and to minimize water loss -Plants obtain thier most of the carbon and oxygen from CO2 -Active mineral absorption helps in creation of water potential gradient -Some ions can move passively by mass flow -Transport proteins of endodermal cells are control points where a plant adjust the quantity and types of solutes that reach to xylem, hence it allow transport of ions in one direction only -Mobile elements---Remobilise from older part to young parts e.g. Mo,Ni,Zn,Mg,N,P,K -Immobile elements---can't mobilise from old to young partsB,S,Ca,Co,Fe -Small amount of P & S |
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