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Transport In Plants

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Introduction

Transport In Plants Need for transport in multicellular plants: - Multicellular plants have too small surface area:volume ratio so diffusion is too slow to provide necessary molecules therefore requires a system to transport nnutrients and products around body - If organism is small, then has a high surface area:volume ratio- all the necessary nutrients and respiratory gases can be taken in by diffusion across body surface. Transpiration - the loss of water from the leaves of a plant Factors affecting transpiration Temperature - increases kinetic energy of water molecules - rate of diffusion and evaporation increases - as temp increases, rate of transpiration increases Light intensity - stomata open at daylight to absorb CO2 - more H2O evaporates - increases in light intensity ...read more.

Middle

Lack of end walls - creates continous column of water Pits- - lateral movement to plant cells Thick walls of lignin- - prevents inward collapse - waterproof - adhesion Water Transport From soil to root hair - soil has few solutes therefore higher water potential - cytoplasm and cell sap have lots of solutes therefore lower water potantial - water therefore moves in by osmosis from a region of high water potential to a region of low water potential, down conc. gradient. Across Cortex - APOPLAST pathway: along cellulose cel walls - SYMPLAST pathway: through living contents i.e vacuole, cytoplasm, plasmadesmata - At the stele, apoplast pathway is blocked - Because of casparian strip of the endodermis prevents water therefore forced to go by ...read more.

Conclusion

cohesion - water molecules stick to eaach other 2) adhesion - water molecules stick to lignin From leaf to atmosphere - Mesophyll tissue has air spaces - walls of mesophyll cells are wet > this water evaporate into air spaces - creating water potential between outside and inside - water diffuses out through stomata Translocation - transport of soluble organic substances from source to sink - source - leaf - sink - roots - sucrose loaded at source by companion cells - H+ is pumped out of the cell by carrier proteins - H+ rapidly diffuses back establishing H+ gradient across membrane - sucrose moves in through by co-transport - sucroseduffuses down concentration gradient through plasmodesmata - water follows in by osmosis => raises hydrostatic pressure - high pressure and mass flow generate => sucrose unloaded at sink ...read more.

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