A lack callose suggests that the sieve elements are more active and therefore can regulate their pores more actively in response to environmental changes .
Callose acts as a block to the sieve pores that are present in both of these sieve elements .
A lack callose suggests that the sieve elements are more active and therefore can regulate sieve elements ' pores more actively in response to environmental changes .
Callose acts as a block to the sieve pores that are present in both of these sieve elements .