Which one of the following plants has unisexual flowers?

In angiosperms, flowers are classified based on the presence of reproductive organs. A flower is considered unisexual if it contains only stamens (male) or only a pistil (female), whereas a bisexual flower contains both [1]. Papaya (Carica papaya) is a classic example of a plant with unisexual flowers and is typically dioecious, meaning male and female flowers are borne on separate individual plants [2]. In contrast, Hibiscus and Mustard (Brassica) are categorized as bisexual flowers because they possess both male and female reproductive parts within the same flower [1]. While Sunflowers (Helianthus annuus) have complex inflorescences where some florets (like ray florets) can be unisexual, the plant is generally characterized by its bisexual disc florets and protandrous nature. Therefore, Papaya is the most definitive example of a plant with unisexual flowers among the given options.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 7: How do Organisms Reproduce? > 7.3.2 Sexual Reproduction in Flowering Plants > p. 120
2. [2] https://www.sciencedirect.com/topics/immunology-and-microbiology/poaceae