Re: How do we de-starch a plant? What does de-starch means?

During photosynthesis many plants form starch grains in the chloroplasts. 
Destarching a plant involves preventing photosynthesis, usually by keeping the 
plant in the dark for 24 to 48 hours until the starch is used by the plant for 
energy or building blocks. Another way to destarch a plant is to deprive it of 
carbon dioxide. A system for depriving plants of carbon dioxide is described in 
the reference.

Leaves are often tested for starch using iodine. The leaf must first be boiled 
in denatured alcohol in a double boiler to remove chlorophyll and cuticle. Be 
careful when boiling alcohol because it is a fire hazard.

Reference
  
Hershey, D.R. 1995. Plant Biology Science Projects. New York: Wiley.