Abstract : Introduction: Toxic soil concentrations of the essential micronutrient boron (B) represent major limitations to crop production worldwide. Plants have a range of defense systems that might be involved in their affinity to resist and tolerate nutrients stress. Materials and methods: The experiments were carried out to study the differential responses in five wheat cultivars to boron toxicity. Results: The fresh and dry matter yield of the test wheat cultivars showed marked decrease as the concentration of boron was increased. Elevated concentration of boron had a notable inhibitory effect on the biosynthesis of pigments fractions in the test wheat cultivars as severely as dry matter gain. The adverse concentration effects of boron on some metabolic responses were clearly displayed by shoot and root systems, exhibited in the elevated rates of proline, hydrogen peroxide and malondialdehyde formation. Potassium leakage was severely affected by boron-stress in some cultivars at all tested concentrations, while in some others a moderate damage was manifested only at the higher boron concentrations. Conclusions: Sakha 93 out of all the different cultivars investigated was found to display the lowest sensitivity to boron-stress, while Gemmeza 9 was the most sensitive one.