Question

Elaborate on the production of artificial seed and illustrate its structure with a well-labelled diagram.

Hint:

To prevent synthetic seeds from drying out during storage, they can be coated with a thin layer of hydrophobic biodegradable polymers like Elvax or co-polymerized resins, which prevent desiccation while allowing respiration.

Answer 1

Step 1: Concept of Artificial Seeds
Artificial seeds (or synthetic seeds) are functionally engineered equivalents of natural seeds. They consist of tissue culture-derived somatic embryos (or shoot tips/axillary buds) encapsulated within a protective, nutrient-rich synthetic gel that acts as the endosperm and seed coat.

Step 2: Production Procedure
The manufacture of synthetic seeds involves four key steps:
1. Embryo Production: Somatic embryogenesis is induced in plant callus cultures to generate large quantities of synchronized, mature somatic embryos.
2. Gel Preparation: The isolated somatic embryos are suspended in a $2% - 3%$ solution of sodium alginate (a viscous gelling polymer). The gel solution is enriched with nutrients, vitamins, and fungicides to protect the embryo.
3. Complexation (Dropping): The alginate-embryo mixture is dropped slowly using a pipette into a complexation bath containing $1% - 2%$ calcium chloride ($CaCl_2$) solution.
4. Ion Exchange and Encapsulation: When sodium alginate contacts calcium chloride, a rapid ion-exchange reaction occurs, replacing sodium ions with calcium ions to form insoluble, rigid beads of calcium alginate gel enclosing a single embryo:
$$2\text{Na-Alginate (soluble)} + \text{Ca}^{2+} \rightarrow \text{Ca-Alginate}_2 \text{ (insoluble gel)} + 2\text{Na}^+$$ Final Answer: Artificial seeds are produced by suspending somatic embryos in sodium alginate and dropping them into a calcium chloride bath, forming protective, insoluble calcium alginate beads.