To solve this problem, we need to identify which substances enhance or induce the fusion of protoplasts.$\newline$Protoplast fusion is a technique used in plant biotechnology to combine the genetic material of two different plant cells.$\newline$Let's analyze each option:$\newline \bullet$Option 1: Sodium chloride and potassium chloride$\newline$ - These are salts that can affect osmotic balance but are not typically used to induce protoplast fusion.$\newline \bullet$Option 2: Polyethylene glycol and sodium nitrate$\newline$ - Polyethylene glycol (PEG) is a fusogen that facilitates the fusion of protoplasts by causing the membranes to adhere and fuse.$\newline$ - Sodium nitrate can also be used to enhance protoplast fusion.$\newline$ - Therefore, this option is correct.$\newline \bullet$Option 3: IAA and kinetin$\newline$ - IAA (Indole-3-acetic acid) and kinetin are plant hormones used for growth and differentiation, not for protoplast fusion.$\newline \bullet$Option 4: IAA and gibberellins$\newline$ - Similar to Option 3, these are plant hormones involved in growth regulation, not in protoplast fusion.$\newline$Based on the analysis, the correct option is Option 2: Polyethylene glycol and sodium nitrate.