Introduction. The date palm tree is one of the fruit trees most cultivated in the Arabian Gulf States.
Bioregulators were used for the quality and productivity improvement of date palm tree fruits. A study was conducted to
assess the relative effectiveness of GA3, NAA, ethephon and a mixture of growth regulators on some fruit
characteristics and productivity of the Barhee date palm tree cultivar. Materials and methods. Five selected
female uniform date palm trees of the cultivar Barhee were pollinated on March 5-15, 1994, 1995 and 1996, by placing
eight fresh male strands on the female spadix center (flower cluster).Ten flower clusters were used on each tree and
divided into five groups of two flower clusters. Each of these groups was subjected to one of the following treatments:
control (water), 150 mg GA3 × L-1, 100 mg NAA × L-1, 1 000 mg ethephon × L-1 and a mixture of these three growth regulators. Then the fruit setting, fruit flesh and dry matter percentages,
the total soluble solids, the fruit ripening, and the fruit weight per bunch and per tree were measured. Results
and discussion. The data showed that the application of GA3 or ethephon on flower clusters of Barhee date palm trees
had no constant effect on fruit characteristics and productivity of trees. NAA or growth regulator mixture applications
on Barhee flower clusters reduced the fruit dry matter and fruit ripening percentages and increased the fruit weight per
bunch and per tree. Conclusion. Treatments of Barhee date palm flower clusters, 20 d after pollination, with NAA or the
specific growth regulator mixture decreased the dry matter percentage and the fruit ripening and increased the fruit
flesh percentage and the date palm tree yield, therefore, these treatments could be recommended to improve the
productivity of date palm trees in the region.