Adjectives

(a)fastidious, exactinghaving complicated nutritional requirements; especially growing only in special artificial cultures“fastidious microorganisms”, “certain highly specialized xerophytes are extremely exacting in their requirements”
(s)stern, strict, exactingsevere and unremitting in making demands“an exacting instructor”, “a stern disciplinarian”, “strict standards”
(s)exigent, exactingrequiring precise accuracy“an exacting job”, “became more exigent over his pronunciation”