Floral development in Phoenix dactylifera

Inflorescence primordia in the date palm (Phoenix dactylifera L.) differentiate within axillary buds in November in the Coachella Valley, California. The rachillae are initiated as small mounds without subtending bracts on the flattened apex of the rachis and are enclosed by the prophyll. A single bract subtends each flower primordium. Flower primordia are initiated in an acropetal sequence along the rachillae. Although mature flowers are functionally unisexual, early development is similar in staminate and pistillate flowers. Six perianth parts are initiated within two alternating whorls: the sepals and the petals. Six stamens are initiated in two alternating whorls of three stamens each, the first opposite the sepals and the second opposite the petals. Lastly, three separate carpels are initiated. Pistillate and staminate flowers are identical and apparently bisexual at this stage. The two flower types diverge developmentally when the stamens become bilobed and elongate in the staminate but not the pistillate flowers. The pistillodes in the staminate flowers form rudimentary stigmatic surfaces at the tip of the carpels and meristematic lumps corresponding to the position of the ovule in normal carpels. The staminodes mature in the pistillate flowers as small triangular projections. Meiosis occurred in staminate and pistillate flowers (in March 1979) when the staminate flowers were about 5 mm long and the pistillate flowers were about 3 mm long.