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herbaceous plants - 85-95% water
woody plants - 75-85% water


1) solvent - dissolves solutes; 
                       the cytosol of the cytoplasm is a water solution of dissolved solutes.

2) reagent - water is used in biochemical reactions, such as photosynthesis.

3) translocation medium - water translocates solutes in xylem and phloem.

4) temperature relations - water is very important in regulating temperature.
    a) stabilizes plants and environment (due to high specific heat)
    b) evaporative cooling (due to heat of vaporization)
    c) releases heat when freezes (due to heat of fusion)
    d) constant temperature during phase change - freezing/melting water/ice water
          stays at 32 F.

5) turgor pressure and growth

    turgor pressure - the positive pressure inside of cells due to water uptake.
    a) turgor pressure is due to osmosis.
    b) turgor pressure keeps cells expanded 
    c) turgor pressure keeps herbaceous plants and plant parts erect
    d) turgor pressure is the driving force for growth in size by causing cell expansion.

growth - an irreversible increase in size or mass.

plasmolysis - shrinkage of individual cells due to loss of turgor pressure that causes
                           a cell to become flaccid.

wilting - excessive water loss that causes loss of plant rigidity; 
                caused by plasmolysis of enough  individual cells to cause the organ to be limp.