in an experiment to show loss in weight during transpiration we take a leafy shoot . suppose you took a single flower with a long stalk dipping in water, instead of a leafy twig . will it serve the purpose ? explain

Dear Student,
Apart from leaves, Floral parts also perform transpiration. 
Flowers perform stomatal transpiration along with cuticular transpiration. That is why a single flower with a long stalk dipped in water would also perform transpiration.
Regards