Gibberellic Acid

• Gibberellic acid is a naturally occurring plant growth hormone that aids in overcoming dormancy, flowering, pollination, fruit set and plant growth. Application of Gibberellic acid to Kabkab date palms at a dilution of 100 mg/L has no statistical benefit regarding the percentage of fruit set at 45, 90 or 135 days after pollination, but it does show minor increases in fruit flesh percentage and bunch weight compared to trees treated with a control solution of distilled water.
  
  

Naphthalene Acetic Acid

• Naphthalene Acetic Acid (NAA) is a synthetic growth hormone regulated by the U.S. Environmental Protection Agency. It is widely used to help plant cuttings form roots. Application to date palms via trunk injection of a 100mg/L NAA solution shows a statistically significant increase in fruit set percentage at 135 days post-pollination while also increasing average fruit length and diameter at harvest, fruit flesh percentage and bunch weight. It does, however, reduce sugar levels in the dates.
  
  

Kinetin

• Kinetin is a cytokinin hormone first isolated in 1955 from the male reproductive cells of herring. Application at a rate of 100mg/L does not show an effect on the fruit set percentage of date palms, and the increase in fruit diameter and bunch weight is not as great as that of trees treated with NAA. Kinetin does not noticeably impact fruit flesh percentage or fruit length, but, unlike NAA, it does not decrease the sugar levels of the dates at harvest.
  
  

Combination Treatment

• While one might expect a combination treatment with Gibberellic acid, NAA and Kinetin to show a synergistic effect, the opposite appears to be true. Combination treatment with all three plant regulators at 100 mg/L rates is not as effective as using NAA alone. There is no significant increase in fruit set percentage over trees treated with distilled water as a control. Increases in fruit size and bunch weight are similar to effects achieved with either Kinetin or Gibberellic acid, and less than those achieved with NAA.