New York Attention must be paid to Franz Xaver Kroetz, the young West German playwright. Three of his works have found their way to the New York stage this season alone, and one critic suggests he is fast becoming as fashionable as his one-time collaborator, the late filmmaker Rainer Werner Fassbinder, whose movies are staples of the art-theater circuit. But is there a grimmer dramatist on the current scene? The answer must be no, judging from the two Kroetz plays that JoAnne Akalaitis has directed. In the wordless ''Request Concert,'' seen at the Interart Theatre a couple of years ago , a middle-class woman comes home from work, straightens her apartment, fixes dinner, listens to the radio, and then, without missing a beat, kills herself. Things aren't much cheerier in ''Through the Leaves,'' the latest Kroetz drama to arrive at the Interart stage. There are two characters this time, a macho workingman and a feisty woman butcher. In her shop and the shabby little room behind, they slog their way through a sad romance, based on her wish for companionship and his need for someone to bully. It's a schematic play, with characters who serve as blunt illustrations of personal and cultural malaise. The drama's resonance comes from its implications for society at large. Victor uses heartless sex (clinically depicted) and blustering ''masculinity'' as weapons because he has been surrounded by such a mentality all his life; Annette puts up with him because that's just the way men are, in her view. She's the more sympathetic of the two, because she has a touch of the poet - jotting wistful hopes in a diary - and a sly intelligence. But both are so isolated emotionally, so trapped by decadent attitudes, so conditioned by brutalizing experiences, that their relationship can't help being fruitless in the end. Although it includes quite a few ironic laughs, the staging of this production underscores the play's harsh naturalism. In the butcher shop Annette chops up pieces of actual meat, while in the bedroom she has graphic sexual bouts with Victor. And every speck of this harrowing realism is the opposite of appetizing or erotic. Still, there's nothing gratuitous about the awfulness on display. The director clearly sees this as a cautionary tale, warning us of the consequences for individuals when insensitive attitudes are not noted and corrected in society at large. It's particularly impressive to note the sense of rugged truth Akalaitis gives this modest kitchen-sink drama - considering that her last show was the huge multimedia spectacle ''The Photographer.'' Further heightening the dark vision of ''Through the Leaves'' is Frederick Neumann's fine-tuned performance as Victor and Ruth Maleczech's brilliant portrayal of Annette, who is searingly alive in every one of the play's brief, pungent scenes. Applause also for Douglas Stein's clever set, Kurt Wilhelm's costumery, L. B. Dallas's ever-surprising sound track, and Frances Aronson's dramatic lighting design. — Through the Leaves. Play by Franz Xaver Kroetz. With Ruth Maleczech and Frederick Neumann. Directed by JoAnne Akalaitis for Interart Theatre and Mabou Mines.