To solve this problem, we need to identify which substance is not an inhibitory substance governing seed dormancy. Let's analyze each option:$\newline \bullet$Abscisic acid:$\newline$ - Abscisic acid (ABA) is a plant hormone that plays a crucial role in seed dormancy by inhibiting seed germination.$\newline$ - It is known for its role in maintaining dormancy and preventing premature germination.$\newline$ - Therefore, it is an inhibitory substance.$\newline \bullet$Phenolic acid:$\newline$ - Phenolic acids are secondary metabolites in plants that can inhibit seed germination and contribute to seed dormancy.$\newline$ - They are known to have allelopathic effects, which can suppress the growth of other plants.$\newline$ - Therefore, they are considered inhibitory substances.$\newline \bullet$Para-ascorbic acid:$\newline$ - Para-ascorbic acid is less commonly discussed in the context of seed dormancy, but it is generally considered to have inhibitory effects on seed germination.$\newline$ - It can act as an antioxidant and may influence dormancy indirectly.$\newline$ - Therefore, it is considered an inhibitory substance.$\newline \bullet$Gibberellic acid:$\newline$ - Gibberellic acid (GA) is a plant hormone that promotes seed germination and breaks seed dormancy.$\newline$ - It counteracts the effects of abscisic acid and stimulates the growth processes necessary for germination.$\newline$ - Therefore, it is not an inhibitory substance.$\newline$Based on the analysis, the substance that is not an inhibitory substance governing seed dormancy is Gibberellic acid.$\newline$Thus, the correct option is Option 4: Gibberellic acid.