Spiral Mechanism in Arenga pinnata

The phyllotaxy of Arenga pinnata is alternate and cyclic revealing two distinct foliar spirals. In some individuals, the two spirals veer to the left and in others, to the right. The number of leaflets on one half of leaf differs from that of the other. This difference is associated with the leaf spirals. Due to the monocarpic nature of the palm, its reproductive phase starts with a terminal inflorescence followed by the development of axillary inflorescences in basipetal order. The sex of the flowers varies with the position of the respective spadices on the palm. That is, the terminal and a few immediate successive spadices produce only female flowers, beyond which each inflorescence produces both female and male flowers, and the last many spadices have only males. The flowers are distributed in clusters of 2 males or 2 males and a female in between, or individually if they are only females. In a cluster of 2 or 3 flowers, The aestivation of sepals of the males varies with their position in the triad. The aestivation pattern in female flowers, however, has an influence on the spirality of the spika on which they are borne.