In the present subjunctive, the -ar and -er stem-changing verbs have the same pattern of stem changes as in the present indicative, only the endings are different.
 

-Ir stem-changing verbs have a slightly different pattern in the subjunctive than in the present indicative. Recall that these are the same verbs that have a different stem change in the preterite, in the third person form. The same stem change seen in the preterite is seen in the subjunctive in the nosotros/as and vosotros/as forms.

Verbs ending in -car, -gar, and -zar have a spelling change in all forms of the present subjunctive, with c > qu, g > gu, and z > c: