Effects of Low Temperature on Potential Net Photosynthesis in Two Field-grown Winter Cereals

Winter wheat and winter barley were tested for their photochemicaland osmotic potentials during the course of one growth cyclein the field. Prolonged winter conditions induced an absolutehigh in potential net photosynthesis (P_N) of winter wheat. Barleyexhibited relatively low P_N rates, which may explain the inferiorfrost hardiness of this species. Osmotic potentials () in bothspecies were quite similar, followed rather uniform trends andwere never extreme. There are doubts, however, whether the assessments truly reflected the osmotic stress on cell membranesin frost-hardened leaves. Increased deposition of cryoprotective assimilates in wheatas the cause of continued frost hardiness is discussed. Triticum aestivum, Hordeum sativum, wheat, barley, potential photosynthesis, winter hardiness