Guar seed prices on Thursday rose by Rs 6 to Rs 3,904 per 10 quintal in futures trade after speculators increased their positions driven by a firm trend at spot market. In the National Commodity and Derivatives Exchange, guar seed for January contracts increased by Rs 6, or 0.15 per cent, to Rs 3,904 per 10 quintal with an open interest of 31,265 lots.Similarly, Guar seed for February delivery traded higher by Rs 10, or 0.25 per cent, to Rs 3,957 per 10 quintal with an open interest of 35,235 lots. According to marketmen, raising of bets by speculators tracking a firm trend in spot market on thin supplies from growing belts mainly led to rise in guar seed prices here.