Isolated polynucleotides having a nucleic acid sequence at least 80% homologous to SEQ ID NO:1, 3, 5, 7, 9, 11, 158, 159, 160, 161, 162-204, 206-211, 214-287 and/or encoding polypeptides having an amino acid sequence at least 80% homologous to SEQ ID NO: 2, 4, 6, 8, 10, 12, 13-56, 58-63, 66-121, 141-156 or 157 are provided. Also provided are methods of utilizing same for increasing the tolerance of a plant to abiotic stresses and/or increasing the biomass, vigor and/or yield of a plant.