POTASSIUM NITRATE ACTS TO STIMULATE AND CONCENTRATE TERMINAL BUD DEVELOPMENT OF 'NAM DOC MAI' TERMINAL SHOOTS INDUCED TO FLOWER BY SOIL PACLOBUTRAZOL TREATMENT

S.A. Oosthuyse, B. Desmet , W. Wongin
Bearing ‘Nam Doc Mai Si Thong’ trees in a non-irrigated orchard in the Chachoengsao Province, Thailand, were either soil-treated in mid-July, 2011, when new terminal shoot development was commencing, with paclobutrazol (PPZ) or were left untreated in this regard. The treated trees were either sprayed or not sprayed with potassium nitrate in October and November to effect terminal bud and inflorescence development. Potassium nitrate (KNO3) was sprayed on October 10, 20 and 27, and on November 3, 2011. In addition, some of the KNO3 sprayed trees were also sprayed with Ethrel/SOP in early September (September 1 and 8) as a measure to prevent early bud development from the new shoots arising after PPZ treatment. Terminal bud swell was first noted on October 20. Tree flowering intensity was recorded on November 10, 24, and on December 8 and 22, 2011. A weather station recorded maximum, average and minimum temperatures, and precipitation.
Ethrel/SOP treatment had no apparent effect on the flowering period or flowering intensity. Only one flush materialized after mid-July from which new shoots or inflorescences developed during October and November. The trees not treated with PPZ and KNO3 (control) generally produced new shoots during Nov. and Dec., whereas those treated with PPZ only, generally produced inflorescences during Nov. and Dec. Here, terminal bud development was not concentrated, occurring over the entire period, and had not occurred or had occurred very little by November 10. In the PPZ treated trees sprayed with KNO3, 40-50% of the terminal shoots exhibited extending or flowering inflorescences on November 10. During the 12 days that followed, terminal shoots showing inflorescence development in the PPZ-only treated trees increased to 58%, attaining the flowering intensity level of the PPZ-treated trees sprayed with KNO3. By November 24, 55-65% of the terminal shoots showed inflorescence development in the treated trees, this increasing to 70-80% by December 22. New shoots as opposed to inflorescences developed from the terminal shoots on the untreated trees in a similar pattern and in the same time period as in the trees treated with PPZ only.
The data clearly indicate that PPZ induced the trees to produce inflorescences, and the KNO3 sprays acted to stimulate and concentrate terminal bud development. Vegetative flushing of the untreated trees during November and December indicates that soil water status and air temperatures were not flower-inductive during the period of the study.
Oosthuyse, S.A., Desmet , B. and Wongin, W. (2015). POTASSIUM NITRATE ACTS TO STIMULATE AND CONCENTRATE TERMINAL BUD DEVELOPMENT OF 'NAM DOC MAI' TERMINAL SHOOTS INDUCED TO FLOWER BY SOIL PACLOBUTRAZOL TREATMENT. Acta Hortic. 1075, 127-134
DOI: 10.17660/ActaHortic.2015.1075.13
https://doi.org/10.17660/ActaHortic.2015.1075.13
Mangiferae indica, flower induction, inflorescence, PPZ, potassium sulphate, Ethephon, terminal shoot
English

Acta Horticulturae