If an antibody is produced for a bacteria, then it would be specific to that bacteria. If the bacteria evolves, an new antibody would have to be produced to mach that new strain of bacteria. I could be wrong, but that is my reasoning. Hope it helps :)
Xylem is one of the two types of transport tissue in vascular plants, phloem being the other. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients.
