Cohen, Y., Department of Fruit Tree Sciences, Volcani Research Center, Agriculture Research Organization, 50250 Bet Dagan, Israel
Aloni, D.D., Department of Fruit Tree Sciences, Volcani Research Center, Agriculture Research Organization, 50250 Bet Dagan, Israel
Adur, U., Department of Fruit Tree Sciences, Volcani Research Center, Agriculture Research Organization, 50250 Bet Dagan, Israel
Hazon, H., Department of Fruit Tree Sciences, Volcani Research Center, Agriculture Research Organization, 50250 Bet Dagan, Israel
Klein, J.D., Department of Agronomy and Natural Resources, Volcani Research Center, Agriculture Research Organization, 50250 Bet Dagan, Israel

The leaves, inflorescences, and fruit bunches of date palm trees develop at the crown, which is the apex of a single trunk that can be up to 25 m tall. Because palm trees are monocots, the leaves and inflorescences are generated deep within the trunk from a single meristem-the palm heart-and are inaccessible for direct bioregulator treatments. We followed the effects of two growth regulators, paclobutrazol and uniconazole-P, on the vegetative growth of young date palm seedlings. Both growth regulators constrained the elongation rate of the leaves and reduced the leaf length. Microscopic analysis of dissected palm hearts revealed that the growth retardants did not affect the generation of new leaves. However, the treatments did change the dimensions of the developing embryonic leaves as well as the shape of the apical meristem. The results suggest the possible future use of growth retardants to reduce trunk height, enabling cheaper, safer, and more efficient management of date palm trees. © 2013 Springer Science+Business Media New York.