Botany and Physiology of Date Palm

The genus Phoenix has agricultural and economic importance mainly due to the use of the fruits of Phoenix dactylifera as food and to the cultivation as ornamental plants of P. canariensis, P. roebelenii, and other species of the genus. Phoenix is made up of between 15 and 20 species of dioecious palm trees with pinnate leaves, which extend from the Cape Verde islands in the Atlantic to Hong Kong, presenting two clearly differentiated groups. The subtropical, in which P. dactylifera, P. canariensis, and P. theophrasti stand out, and whose populations are found between latitudes 20° and 40° in the northern hemisphere, is the one that presents the greatest global economic relevance. The tropical group, whose populations are mainly found between the tropics of Cancer and Capricorn in Africa and Asia, and in which P. loureiroi, P. reclinata, and P. paludosa stand out, also presents local relevance. This chapter reviews the outstanding aspects of the botany and physiology of the species of the genus Phoenix and especially of P. dactylifera. The morphological and genetic heterogeneity of currently accepted Phoenix taxa is quite uneven, notably found in the various geographic groups of P. dactylifera and P. loureiroi. From the botanical point of view, detailed morphological studies are still necessary in the field or germplasm banks of some Phoenix that have been described at the species level, but which are possibly hybrids or varieties of other species, notably in the Horn of Africa, the Arabian Peninsula, and the Indian Ocean islands. The physiology of Phoenix has been widely studied in the aspects that fundamentally affect the development of the plant under stress conditions (hydric, thermal, saline) and the production, quantity, and quality of the fruit. However, there are still many aspects remaining to be clarified, as is the case with metaxenia, which is the influence of the specific pollen that fertilizes the female flower on the morphology and quality of the fruit. This is despite the fact that in its entirety, except for the embryo in the seed, the fruit is made up of maternal tissues. Studies of symbionts at the level of the roots of the palm tree have provided information of considerable interest, notably in the case of mycorrhizae, which point to the beneficial effect of these symbioses for the plant in terms of improving nutrient availability and resistance to stress conditions.