Microsporogenesis, megasporogenesis, and gametophyte development in the threatened tree Buchanania lanzan (Anacardiaceae)

Buchanania lanzan (Spreng.), a member of the Anacardiaceae, is an ecologically and economically important tree species native to the dry deciduous and mixed forests of India, with a notable distribution in the Western Ghats biodiversity hotspot. Despite its significance, its reproductive biology has remained poorly understood, with several aspects reported inconsistently. The present study provides a comprehensive and sequential account of microsporogenesis, megasporogenesis, and male and female gametophyte development in B. lanzan based on detailed histological investigations using light microscopy, fluorescence microscopy, and scanning electron microscopy (SEM), thereby resolving earlier ambiguities. Anther development is tetrasporangiate, and microsporogenesis occurs normally. Microspore mother cells undergo normal meiosis to produce predominantly tetrahedral tetrads, which subsequently develop into bicellular pollen grains at anthesis. Fluorescence staining showed positively stained pollen grains, while SEM analysis revealed distinct exine surface patterns on the pollen wall. Specialized features of the anther wall, including cuticular outgrowths, suggest multifunctional roles in protection, mechanical support, and possible pollinator interactions, comparable to those reported in related genera such as Mangifera and Anacardium. Ovules are anatropous, bitegmic, and crassinucellate. Megasporogenesis results in a linear tetrad, with the chalazal megaspore developing into a Polygonum-type mature female gametophyte. The outer integument exhibits a distinctive growth pattern that may enhance protection of the developing embryo sac. This study provides essential baseline data on reproductive development in B. lanzan, supporting conservation and sustainable management of this threatened species.