Lab Gallery: Biochemistry

Starch is a polysaccharide consisting of a large number of glucose units jointed by glycosidic bond. A tiny well packed storehouse of starch, made by plants through  photosynthesis is known as starch grain. The grains are means for plants to store energy.  The grains differ in their size, shape, and position of hilum in plants.

Hilum is the point around which layers of starch are deposited. All grain have hilum & depending on the position of hilum two types of grains are found.

  1. Concentric (hilum at middle point)
  2. Acentric (hilum at one side)

Depending on number of grains, two type of starch grain are found.

  1. Simple (single grain)
  2. Compound (cluster of grain)

Since Plants store starch grain in roots, bulbs, tubers, rhizomes as well as seed and stems, to extract the starch, these storage organs are crushed, the starch grain are released from destroyed cell.

1. Starch Grains of Potato (Solanum tuberosum)
Specimen: Starch grains of PotatoDescription:

  • Relatively large granules compared to others. Range between 30-100 µm.
  • Transparent, colorless & oval shaped granule.
  • Simple  & acentric hilum.
Magnification: 40x
Dye: 1 drop iodine solution
Courtesy: Arohi Roy Dipa

 

2. Starch Grains of Maize
Specimen: Starch Grains of MaizeDescription:

  • Both small and large granule ranges 1-7 µm & 15-20 µm respectively.
  • Yellowish white colored, Polyhedral to sub-spherical shaped granule.
  • Simple, concentric star shaped hilum.
Magnification: 40x
Dye: 1 drop iodine solution
Courtesy: Arohi Roy Dipa

 

3. Starch Grains of Rice (Oryza sativa)
Specimen: Starch Grains of RiceDescription:

  • The smallest granule compared to others ranges between 2-8 µm.
  • Angular & polygonal shape with smooth surface.
  • Compound grain with concentric hilum.
  • Tend to clump in group of a cluster of granules.
Magnification: 40x
Dye: 1 drop iodine solution
Courtesy: Wikipedia: Starch analysis

 

4. Starch Grains of Wheat
Specimen: Starch Grains of WheatDescription:

  • Granule size ranges between 3-40 µm.
  • Oval shaped, grayish white colored granule.
  • Simple, concentric hilum present.
Magnification: 40x
Dye: 1 drop iodine solution
Courtesy: