To solve this problem, we need to analyze each statement to determine which one is not true. Let's evaluate each option:$\newline \bullet$Option 1: Tapetum helps in the dehiscence of anther.$\newline$ - The tapetum is the innermost layer of the anther wall and provides nourishment to developing pollen grains.$\newline$ - It also plays a role in the formation of the pollen wall, but it is not directly involved in the dehiscence of the anther.$\newline$ - Therefore, this statement is not true.$\newline \bullet$Option 2: Exine of pollen grains is made up of sporopollenin.$\newline$ - Sporopollenin is a highly durable polymer that makes up the exine layer of pollen grains, providing resistance to environmental stress.$\newline$ - This statement is true.$\newline \bullet$Option 3: Pollen grains of many species cause severe allergies.$\newline$ - Pollen grains are known to cause allergies in many individuals, especially those with pollen allergies or hay fever.$\newline$ - This statement is true.$\newline \bullet$Option 4: Stored pollen in liquid nitrogen can be used in the crop breeding programmes.$\newline$ - Pollen can be stored in liquid nitrogen for long-term preservation and used in crop breeding programs.$\newline$ - This statement is true.$\newline$Therefore, the statement that is not true is Option 1: Tapetum helps in the dehiscence of anther.$\newline$The correct option is Option 1.