Tokyo stocks opened slightly lower Tuesday, as a cautious mood prevailed ahead of the conclusion of the Bank of Japan’s two-day policy meeting later in the day. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average fell 69.06 points, or 0.21 percent, from Monday to 32,689.92. The broader Topix index was down 9.21 points, or 0.40 percent, at 2,307.65. On the top-tier Prime Market, decliners were led by iron and steel, marine transportation and air transportation issues. At 9 a.m., the U.S. dollar fetched 142.64-67 yen compared with 142.75-85 yen in New York and 142.38-40 yen in…