Influence of root chilling on winter and spring wheat growth and carbon dioxide assimilation

摘要

Growth and carbon dioxide (CO_2) assimilation responses of winter wheat (Triticum aestivum L. var. Chisholm) and spring wheat (var. Mexico 82) to root chilling were compared and contrasted. Seedlings were grown in a growth chamber at 350 #mu#mol m~(-2) s~(-1) photon flux density, 45-50 percent relative humidity and 25 deg C for 4 weeks. The rootzone temperature of the experimental plants was then lowered from 25 to 5 deg C for 7 days with the shoots remaining at a constant 25 deg C. Soluble sugar,starch and fructan concentrations were determined to understand the physiological bases of the effects of these conditions on the two varieties. In addition, activities of sucrose phosphate synthase (SPS), sucrose synthase (SS) and acid invertase were examined. The effects of root chilling on leaf conductance and internal CO_2 were also investigated. Growth of both plant varieties decreased at the lower root-zone temperature, but this reduction was most pronounced in the spring wheat. Both varieties showed significant reductions in CO_2 assimilation, leaf conductance and internal CO_2, concentration in response to lower root-zone temperatures. Total soluble sugar, starch and fructan concentrations in the shoots and roots increased in both varieties atthe 5 deg C root-zone. In addition, sucrose concentration in the shoots of the plants exposed to lower root-zone temperatures increased significantly in both varieties. Invertase and SPS activity decreased in the shoots of both varieties at a low root-zone temperatute, whereas SS activity increased in the shoots of both varieties.