What is the required temperature for the induction of callus from an explant?

What is tissue culture useful for?

Which method is used to develop new plant species in botanical gardens?

"Give me a living cell of any plant and $I$ will give you a thousand plants of the same type". Is this only a slogan or is it scientifically possible? Write your comments and justify them.

Shoot tip culture is preferred for the international exchange of germplasm because:

During tissue culture,the growth hormones are provided to callus to induce . . . . . . .