Chardakov Technique Plant Physiology UNI

Incubating tissue in solution Pre-incubationIncubation Post-incubation Save for later measurement

Did solution change concentration? Solutes stay the same If water left or entered tissue –Water also entered or left solution –Solution becomes more dilute or more concentrated Changes in density of solution –More dilute = less dense –More concentrated = more dense Density change detects concentration change

Compare solution densities Pre-incubation vs post-incubation Denser solution sinks to bottom Problem: both are clear Pre-incubation Post-incubation

Dye one solution so we can see it Pre-incubation Post-incubation Dyed pre-incubation Suspend one drop Does the drop rise? stay? fall?

Drop movement tells us If solution density has changed If solution concentration has changed Whether water has been lost to tissue or gained from it Whether WP was higher at the start in tissue or in the solution

If the drop doesn’t move? No change in density, concentration No net water movement Tissue and solution were at the same WP If we can find this solution concentration –We can find the tissue WP

Tissue Water Potential Measurements Plant Physiology UNI

Tissue in solution Water movement? 3 possibilities –Water moves into tissue –Water moves out of tissue –Water does not move (= moves equally in both directions) Water always moves from higher to lower water potential (WP)

How could you tell? What would happen to The size of the tissue? –Water moving in, out or no net movement The concentration of the solution? –Water moving in, out or no net movement The stiffness of the cells? –Water moving in, out or no net movement Let’s make some predictions…

If water moves into tissue From higher to lower WP Tissue must have lower WP than solution at start 3 consequences –Tissue gets bigger –Solution gets more concentrated –Cells get more rigid

If water moves out of tissue From higher to lower WP Tissue must have higher WP than solution at start 3 consequences –Tissue gets smaller –Solution gets less concentrated –Cells get less rigid

If no net water movement between tissue and solution No movement of water = no difference in WP Tissue must have same WP as solution at start No changes –Tissue stays same size –Solution stays same concentration –Cells stay equally rigid

What did you get? Tissue size? Solution concentration change? Cell (tissue) rigidity?