what is bolting ?

[ten]

dear ron,

i think i have a problem with my cabbage on hydroponics. after 5 weeks, it just grown by 3 nodes. i dont think its a very good progress.
somebody told me that i might be experiencing bolting. what is bolting ? how can i prevent it and what are the physical manifestation of bolting ?
btw, i am in Philippines where temperature runs above 32 C in the middle of the day. i keep the system cool down by placing it indoor with indoor lamps. i cool the roots with temperature control nutrient solution.
o2ten