Temporal Distinction between Male and Female Floral Organ Development in Nicotiana tabacum cv. Xanthi (Solanaceae).

Hongli Chang,Fengjie Sun

doi:10.3390/plants9010127

Hongli Chang, Fengjie Sun

Open Access

https://doi.org/10.3390/plants9010127

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Abstract

Early floral developmental investigations provide crucial evidence for phylogenetic and molecular studies of plants. The developmental and evolutionary mechanisms underlying the variations in floral organs are critical for a thorough understanding of the diversification of flowers. Ontogenetic comparisons between anthers and pistil within single flowers were characterized over time in Nicotiana tabacum cv. Xanthi. The ages of 42 tobacco flower or flower primordia were estimated using corolla growth analysis. Results showed that the protodermal layer in carpel primordia contributes to carpel development by both anticlinal and periclinal divisions. Periclinal divisions in the hypodermal layer of the placenta were observed around 4.8 ± 1.3 days after the formation of early carpel primordia (ECP) and ovule initiation occurred 10.0 ± 0.5 days after ECP. Meiosis in anthers and ovules began about 8.9 ± 1.1 days and 14.4 ± 1.3 days after ECP, respectively. Results showed an evident temporal distinction between megasporogenesis and microsporogenesis. Flower ages spanned a 17-day interval, starting with flower primordia containing the ECP and anther primordia to the tetrad stage of meiosis in megasporocytes and the bicellular stage in pollen grains. These results establish a solid foundation for future studies in order to identify the developmental and molecular mechanisms responsible for the mating system in tobacco.

Highlights

In angiosperms, various factors affect the successful pollination and subsequent fertilization of the egg in the female gametophyte
Selfing is commonly found in diverse groups of angiosperms and functions in different forms, including geitonogamy [12,13], autogamy, and cleistogamy [3,9]
In some flowers, carpel tips were not fused, but inner tapetum was formed in the anthers. These results indicated that the process of carpel fusion is too protracted in tobacco to be a good morphological marker for staging primordia during early floral development

Summary

Introduction

Various factors affect the successful pollination and subsequent fertilization of the egg in the female gametophyte (i.e., embryo sac). The mating patterns are greatly influenced by the phenotypic variations in floral traits, such as herkogamy (the spatial separation of anthers and stigma) and dichogamy (the temporal separation of male and female phases) [1,2,3,4,5,6,7,8], cleistogamy (the self-fertilization within a permanently closed flower) [3,9], and heterostyly (styles of different lengths relative to the stamens in the flowers of different plants) [10,11]. Selfing is commonly found in diverse groups of angiosperms and functions in different forms, including geitonogamy (pollen is transferred to a different flower on the same plant) [12,13], autogamy (pollen is deposited on the stigma of the same flower during floral development), and cleistogamy (obligated self-pollination in closed, bud-like flowers) [3,9].

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