Will Elevated Atmospheric CO2 Temporarily or Persistently Alter the Dry Mass Allocation Between Shoot and Root and Among Rooting Zones of Field Grown Wheat?.

o    Elevated atmospheric CO2 (Ca) may temporarily or persistently shift the root to shoot relationship of graminaceous species and the spatial distribution of their root systems.
o    Two, 2-yr studies were conducted on spring wheat [hard red; Triticum aestivum (L). cv. Yecora Rojo] grown in an open field under 360-370 and 550 µmol mol-1 Ca and under ample water and N supply. The effect of elevated Ca on dry weight allocation between the root and shoot and amongst rooting zones was determined from the three-leaf growth stage until physiological maturity.
o    The effects of elevated Ca on the root to shoot relationship oscillated between positive and negative extremes throughout the ontogeny. If any shift occurred during one growth stage, it was often counter balanced by an inverse shift by the next one. Elevated Ca stimulated branching of roots and the exploration of the soil by roots during vegetative growth. However, this stimulatory effect was temporary and ceased thereafter.
o    Changes in the dry weight allocation between root and shoot and amongst rooting sections because of elevated Ca occurred only occasionally and were temporary in nature depending on the ontogeny of the wheat crop and its present and past growth conditions.