Plant in which chromosomal basisi of sex determination was discovered first is

Options

A. Rumex
B. Melandrium
C. Caccinia
D. Sphaerocarplus

Answer

**Step-by-Step Solution:**

1. **Identify the Question**: The question asks for the plant in which the chromosomal basis of sex determination was first discovered.

2. **Understand the Context**: The discovery pertains to a dioecious plant, meaning that male and female reproductive organs are found on separate plants.

3. **Recall the Plant Name**: The plant in which this discovery was made is known as Melandrium, specifically Melandrium album.

4. **Update on Nomenclature**: It is important to note that the plant has since been reclassified and is now referred to as Selenylatifolia.

5. **Understand the Chromosomal Mechanism**: The sex determination in this plant follows an XXXY chromosomal pattern, similar to that found in humans and Drosophila.

6. **Explain the X:A Ratio**: In this plant, sex determination is based on the X:A (X to autosome) ratio. Males have a ratio of 0.5 (one X chromosome and two sets of autosomes), while females have a ratio of 1 (two X chromosomes and two sets of autosomes).

7. **Conclude with the Correct Answer**: Therefore, the correct answer to the question is Melandrium (now Selenylatifolia).

**Final Answer**: The plant in which the chromosomal basis of sex determination was first discovered is Melandrium (now Selenylatifolia).

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