In bottom up parsing the string will keep on getting reduced(or handles will prune) resulting in bottom up parse tree.
eg- consider the code- if (condition)----→ if(condition) + statement / Φ
so here for the top down parser will result in infinite left recursive tree until condition isn’t satisfied.
if(condition)
/\
if(condition) statement <----- left recursive tree
/\
if(condition) statement
/\
and so on
but in bottom up parser there is reduction of string resulting as follows-
if(condition)
/\ ᐎ
if(condition) + statement || bottom to up movement
||