Starch Storage Parenchyma

Two Protocols of starch localization are given below and illustrated by micrographs

First example: staining of starch in potato chair using fresh sections and Lugol reagent.
Starch is an energy reserve for potato and consists of long chains of glucose molecules. It contains a mixture of amylose and amylopectin and is present in the form of granules varying in size from 1 to ~ 100 µm. Inside the granule the starch molecules are arranged into concentric layers around a central point called hilum, starting point for the accumulation of amylose and amylopectin

Material required
Watch glasses
Thin Razor blade
Brush to collect sections.
Lugol: Iodine/Potassium iodide solution

Preparation of Lugol
2% Potassium iodide (KI) and 0,2 % diiode (I2)

Protocol
Sections as thin as possible are made with a thin and soft razor blade in a piece of potato chair.
The sections are directly transferred with a paint brush into a watch glass containing water. They are then immersed into a drop of Lugol solution for 1 min and directly collected on a microscope slide in a drop of water. They are covered delicately with a coverslip and observed with a light microscope. Starch grains appear as blue to purple particles.

Micrographs illustrating Lugol staining
On the left parenchyma cells that compose the potato chair with starch grains-stained blue purple. They are contained in unstained amyloplasts and appear as oval structures.
On the right higher magnification picture of starch grains (A). They appear composed of a series of concentric layers.
The starch grains are contained in amyloplasts that are colorless. Hilum is visible in the center of a few strach grains.