What is cavitation in propeller?

Tip vortex propeller cavitation is due to low pressure within the vortices shed at the blade tips. Boss or hub vortex cavitation is usually due to a high angle of incidence between the direction of flow of the water and the blade leading edge in way.

What is cavitation in plants?

Cavitation occurs in the xylem of vascular plants when the tension of water within the xylem becomes so great that liquid water (or sap) vaporizes locally and dissolved air within the water expands to fill either the vessel elements or tracheids.Plants are generally able to repair cavitated xylem in a number of ways.
What is cavitation and how is it formed and how to prevent/ avoid cavitation in a hydraulic machine? The formation, growth and collapse of vapour filled cavities or bubbles in a flowing liquid due to local fall in fluid pressure is called cavitation. The cavitation in a hydraulic machine affects in the following ways:

(a) It causes noise and vibration of various parts.
(b) It makes surface rough.
(c) It reduces the discharge of a turbine.
(d) It causes sudden drop in power output and efficiency.

The cavitation in reaction turbines can be avoided to a great extent by using the following methods:

(a) By installing the turbine below the tail race level.
(b) By using stainless steel runner of the turbine.
(c) By providing highly polished blades to the runner.
(d) By running the turbine runner to the designed speed.