Pollen and anther development in Nelumbo (Nelumbonaceae)

Area of Science:

• * Botany and Plant Science
• * Developmental Biology
• * Systematic Botany

Background:

• * The Nelumbonaceae family, comprising Nelumbo nucifera and Nelumbo lutea, has uncertain phylogenetic placement, historically linked to Nymphaeales but recently allied with lower eudicots like Platanus.
• * Pollen and anther development are crucial for understanding angiosperm phylogeny, yet these processes remain largely uncharacterized in Nelumbo.

Purpose of the Study:

• * To provide the first comprehensive morphological description of pollen and anther ontogeny in Nelumbo lutea.
• * To compare these developmental events with those in Nymphaeales and Platanus to clarify Nelumbo's systematic and phylogenetic position.

Main Methods:

• * Morphological description of pollen and anther development stages in Nelumbo lutea.
• * Documentation of key ontogenetic events from sporogenous tissue to mature pollen and anther structures.
• * Comparative analysis of Nelumbo's ontogeny with related plant groups.

Main Results:

• * Detailed ontogenetic sequence including microspore mother cell coat, callose wall, tetrahedral/tetragonal tetrads, and primexine formation.
• * Exine development characterized by tectate-columellate ectexine, lamellate endexine, and an unusual granular layer; rapid two-layered intine formation.
• * Anther development shows degradation of the secretory tapetum and formation of U-shaped endothecial thickenings; pollen grains are predominantly tricolpate with some monosulcate and diaperturate forms.

Conclusions:

• * Nelumbo lutea exhibits unique pollen and anther ontogenetic features, including late aperture ontogeny and aperture variability.
• * While sharing some characters with Nymphaeales and Platanus, Nelumbo's overall ontogenetic sequence differs significantly.
• * The findings contribute to a better understanding of angiosperm phylogeny and the systematic relationships of Nelumbo.