Effects of selenate addition on selenium accumulation and plant growth of two Prunus rootstock genotypes

A pot experiment was conducted with two Prunus genotypes (GF 677 and Mr.S.2/5, commercial rootstocks for peach), which are widely used in Italy and other European countries. Selenium (Se) was added as sodium selenate to 3‐month‐old micropropagated plants at a rate of 0 (control), 1.0, 2.5, and 5.0 mg Se (kg soil)^–1. Plant growth, gas exchange, and Se accumulation were studied. Selenium added at a rate of 2.5 and 5.0 mg Se kg^–1 appeared to be highly toxic for the two young peach rootstocks. Thirty‐three days after the treatment, the plants showed a high mortality rate. The fast growing rootstock, GF 677, appeared to be more sensitive to Se toxicity, the mortality rate reaching 52%. The higher the Se concentration in the soil, the higher it also was in the plant. In general, both genotypes were able to take up Se and to translocate high amounts from root to leaf. After selenate addition to the soil, both GF 677 and Mr.S.2/5 plants showed reduced plant growth with the highest Se treatments. Furthermore, Se induced a partial stomatal closure, as evidenced by the values of stomatal conductance, resulting in a reduction in net assimilation, and thus a decrease in dry‐matter production. Selenate applied at a low rate (1 mg Se kg^–1) stimulated plant growth in GF 677. One year after the Se treatment, a remobilization of Se from the storage organs to the young shoots was detected. This study demonstrates genotypic variation in Se uptake and accumulation in peach rootstocks.