Pronunciation: [sˈɛksa͡ɪn] (IPA) 
The word "sexine" refers to the outer layer of a pollen grain. It is spelled with a "s" sound, followed by the "e" sound as in "bet", then a "ks" sound, followed by the "ih" sound as in "sit", and finally the "n" sound. The IPA phonetic transcription for "sexine" is /ˈsɛksɪn/. This word derives from the Latin word "sexus", meaning "six", and refers to the six layers typically found in the sexine of a pollen grain.
Sexine refers to the specialized outer layer of the pollen grain found in certain plant species. It is a highly intricate and elaborate structure that plays a crucial role in protecting and transporting the male gametes during the process of pollination. The sexine layer is composed of a complex mixture of proteins, lipids, and sporopollenin, a highly resistant and durable substance.
Structurally, sexine is characterized by its intricate sculpturing, which can include various patterns, pores, ridges, and ornamentations. These patterns are unique to each plant species and can be utilized for taxonomic identification purposes. The sexine layer is surrounded by another layer called the nexine and together they constitute the exine, the outermost layer of the pollen grain.
The main function of the sexine layer is to ensure successful pollen dispersal and fertilization. Its sculpturing and durable composition enable the pollen grain to withstand harsh environmental conditions, such as desiccation and UV radiation. Additionally, the distinctive patterns on the sexine layer aid in the adhesion of pollen grains to pollinators, facilitating efficient pollen transfer between flowers.
The study of sexine is an essential part of palynology, the branch of science that focuses on the study of pollen grains and spores. By analyzing the sexine characteristics of fossilized pollen grains, scientists can gain insight into past plant distributions, environmental conditions, and evolutionary relationships.
