Distribution of newly fixed 14C-photoassimilate under deficit irrigation and half-root stress in peach trees

Two-year-old potted peach 'Zaojiubao' (Prunus persica L. Batsch) trees on wild P. persica rootstock were subjected either to regulated deficit irrigation (RDI), in which trees were water stressed during fruit pit hardening (stage II) followed by rewatering during the final rapid fruit growth stage (stage III), or to half-root stress (HRS) treatments during the same two stages. To investigate the allocation of carbon assimilates among sink organs, shoots were fed with 14CO2 twice, either during stage II or stage III. The distribution coefficient (K) represented the competitive sink strength. RDI and HRS induced an altered allocation pattern of 14C-assimilates. The import to shoot apexes was reduced. However, there were no significant reduction in fruit diameter and weight. Moreover, the Ks of the fruit subparts of RDI and HRS treated trees were similar to or sometimes higher than those of CK trees. There were more 14C-assimilates and higher K values of seeds from RDI trees during stage III compared with CK. In addition, stressed roots seemed to have stronger abilities to attract 14C-assimilates. It is concluded that RDI and HRS resulted in a decreased sink activity in the shoot and a change of carbon allocation toward stressed roots and seeds without negative effects on fruit growth.