Maryland Gov. Harry Hughes bestowed an election-year plum on Montgomery County today by adding $6.2 million to his capital budget for a new elementary school in booming south Germantown and expansion of Gaithersburg High School.

Hughes announced the additional construction funding, which doubles the amount he had previously designated for Montgomery, at a 20-minute meeting this afternoon with more than a dozen Montgomery County members of the House of Delegates and state Senate.

Hughes' addition to his capital budget for the fiscal year that starts in July still must be approved by the legislature and state Board of Public Works.

The announcement came less than a month after the county's legislative leaders, County Executive Charles W. Gilchrist and County Council President William E. Hanna Jr., met privately with the governor to appeal for more school construction money.

"These projects will help meet the need for more classroom space in a rapidly growing area," Hughes said in a prepared statement.

The additional $3.8 million, which reimburses the county for construction of the new South Germantown Elementary School, and $2.4 million for the expansion of Gaithersburg High School raises to $11.5 million the amount that many Montgomery delegates and senators can say they delivered to their home districts as they campaign for reelection in the fall.

Last month, when Hughes earmarked $5.3 million for Montgomery in his $35 million statewide school construction program, county politicians complained that the governor should have been more generous.

The county, they noted, had already advanced $16.6 million to pay for the Germantown and Gaithersburg projects, as well as other new classrooms to keep pace with a "baby boomlet" that has crowded many schools, particularly in lower grades. Montgomery's elementary school population jumped from 41,000 in 1983 to 46,000 last year, and is expected to climb to 59,000 by 1991.

Hughes took note of Montgomery's own expenditures today, saying his new allocation "recognizes the extraordinary effort that Montgomery County has already made to keep up with demands for school facilities."

Some Montgomery officials noted today that the governor's largesse could look good on his record if he launches his expected bid for a U.S. Senate seat.

"What appeared to be neglect on his part -- for Montgomery County -- would not bode well for him in an election year," said Montgomery Del. Ida G. Ruben (D), who with state Sen. Sidney Kramer (D) led the fight for extra construction funds.

More important than the politics of the construction aid is the need the money will fill in the mushrooming Germantown area, officials said.

For example, Lake Seneca Elementary School opened there in September with 885 students -- 121 percent of its capacity. If no other elementary school is built in Germantown, Lake Seneca is projected to have 1,215 students in the fall, or 165 percent of its capacity. South Germantown Elementary is scheduled for completion this year.

Most of the new Montgomery grant was made possible by delaying construction of a proposed $8.4 million office complex for the state Department of Natural Resources in Annapolis. An aide to Hughes said the office complex had been a favorite target of the General Assembly for the last several years, dying as legislators converted the budget item into pork barrel projects for their own jurisdictions.