Biochemical changes during seed germination

1. Nucleic acid

• During imbibition, there is a rapid decrease of DNA and RNA contents in the endosperm with a simultaneous increase in the embryonic axis
• High concentration of RNA in the embryonic axis precedes cell division
• Due to more cell division DNA content is increased

2. Carbohydrates

• Insoluble carbohydrates like starch are the important reserve food of cereals in the endosperm
• During germination, starch is hydrolysed first into maltose in the presence of alpha-amylase and ß – amylase and then maltose is converted into glucose by maltase
• The glucose is further converted into soluble sucrose and transported to growing embryonic axis

3. Lipids

• Many plants like castor bean, peanut, etc, store large amount of lipids or fats as reserve food in their seeds
• During germination, the fats are hydrolyzed into fatty acids and glycerol by lipase enzyme
• Fatty acids are further converted into acetyl – COA by the process of ß – oxidation
• The acetyl COA is further converted into sucrose via glyoxylate cycle and is transported to the growing embryonic axis

4. Proteins

• Some plants store proteins as reserve food in their seeds
• Proteins are hydrolysed into amino acids by peptidase enzyme
• The amino acids may either provide energy by oxidation after deamination (removal of amino group) or may be utilized in the synthesis of new proteins

5. In organic nutrients

• A number of inorganic nutrients such as phosphate, calcium, magnesium and potassium are also stored in seeds in the form of phytin

• These stored nutrients are liberated during germination due to the activity of various phosphatases including phytase