I need help ASAP

[Evelyn Thai]

Hello. I would really appreciate any help. I need to know the exact
scientific reason why:

    1) removing the leaves of plants after transplanting helps the plant to
survive.

    2) why experts in flower arranging advise recutting the stems of flowers
while holding them under water.

    3) Why some florists add ordinary table sugar to the water in which cut
flowers are placed and why the flowers will subsequently remain fresh for
several weeks.

Thanks a billion for your time and assistance!

Sincerely,

E.Thai