Definitely there will be profound physiological changes due to mechanical stress.You can check the increase in ethylene concentration, decrease in auxin and gibberellin concentration.further you can notice morphological changes like reduction in stem elongation,leaf elongation,petiole length etc. Study on mechanical stress in open field conditions is however not possible due to many environmental constrains like wind, heavy rain etc.Thus study is suitable under in house conditions.   

The above mentioned conditions will restrict the resource allocation towards flowering and thus would affect the reproductive growth in plant.

Many thanks TAREQ A Wani

Thanks for information.

Sir how pinching increase flower size?

When you pinch the plant so you have discarded the first flowering means the plant will have more time to store more photosynthates rather than utilizing these in reproductive growth so when the plant start flowering these stored food (in larger quantity) material will be diverted toward the flower and ultimately the flower size will be larger