We present a simple scaling theory to describe the conformational properties of semiflexible polymers grafted on a flat surface. For orientation-dependent interactions between polymer segments, we analyzed the physical properties of a polymer brush from the collapsed to strongly stretched regimes. Our analysis predicts first-order isotropic-nematic phase transitions between isotropically and nematically collapsed brushes, and between stretched and nematically collapsed brushes. It is also found that the orientational interactions would raise the effective a temperature as compared with the isotropic counterparts.