For reasons ranging from reverence to fear, many stores in downtown Washington will be closed today for the 20th anniversary March on Washington.

Some merchants are closing in honor of the late Rev. Martin Luther King Jr. and the aims of the civil rights movement, while others are closing out of fear of a repeat of the looting and violence that occurred in the downtown area last November after an anti-Ku Klux Klan demonstration.

While large downtown department stores, such as Woodward & Lothrup, Garfinckel's and Hecht's, will remain open for regular Saturday hours, it is a "mixed bag" for closings among other stores in the downtown area, according to a spokesman for the Greater Washington Board of Trade.

Melart Jewelers, 601 13th St. NW, is one of several jewelry shops in the downtown area that will be closed. The store was struck last Nov. 27 by the looting that broke out after anti-Klan protesters were denied a confrontation with Klan members.

"We are closing mostly because of what happened with our front window being broken out and everything," store manager Bob Getz said. "We didn't want to take a chance of that happening again."

Getz said he decided to close the store after a small group of local merchants, fearing another outbreak of violence, contacted him in early August to say they would be closing for the march.

Some of the stores hit hardest last November, however, planned to be open today. They include Sholl's New Cafeteria, 1433 K St. NW, where plate-glass windows were shattered by looters, and Big Wheel Bikes, 1004 Vermont Ave. NW, where windows were broken and several bikes were stolen.

"It is our regular business day. There is no reason to close. It is a peaceful march, and we are peaceful people," said Jean Chiotti, manager at Big Wheels.

Both fear of looting and respect for the civil rights movement figured in Larry Greenberg's decision to close Jewel Fare, a store he owns at 1220 G St. NW.

"Sure, part of it is the fear of violence," Greenberg said. "But I'm doing it, too, to honor Martin Luther King and the whole idea of the March on Washington. This one day out of 20 years is in respect."

The National Gallery of Art and the museums of the Smithsonian Institution will be open today for regular summer hours.

Nearly all federal buildings will be closed, an exception being the Aquarium Commerce Building between E Street and Constitution Avenue NW.

According to the Board of Trade, stores in suburban areas will be open during normal business hours, as will most stores along the Connecticut Avenue corridor. Not many shoppers, however, are expected to brave the congestion likely to result from a crowd predicted to number more than 250,000 people.

Several merchants said yesterday they were closing today because their employes may not be able to get through the crowds in time for work.

"My girls have to use the subway to get in in the morning, they have to get lunch, they have to go home. All my girls are afraid that transportation is going to be bad," said Harry Shapiro, owner of Maison's, a hat shop at 1215 G St. NW. "One day is not going to make us or break us."