**Explanation:**

**Chromosome Number in Leaf Tip Cells:**
The chromosome number in leaf tip cells represents the total number of chromosomes found in the somatic cells of a plant. It is typically represented as 2n, where n is the number of chromosomes in a haploid set.

**Pollen Tetrad:**
A pollen tetrad refers to a group of four pollen grains that are produced by the meiotic division of a single microspore mother cell. Each of these pollen grains contains a haploid set of chromosomes.

**Given Information:**
In the given plant species, each cell of the pollen tetrad contains 6 chromosomes. We need to determine the chromosome number in the leaf tip cells of this species.

**Solution:**
To find the chromosome number in the leaf tip cells, we need to consider the ploidy level of the cells involved.

1. Each cell of the pollen tetrad contains a haploid set of chromosomes. Therefore, the chromosome number in each pollen grain is 6.

2. The pollen grains are produced by the meiotic division of a single microspore mother cell. The meiotic division involves two rounds of cell division (meiosis I and meiosis II), resulting in the formation of four haploid cells.

3. As each pollen grain contains a haploid set of chromosomes, the microspore mother cell must be diploid (2n) to provide the necessary genetic material.

4. Therefore, the chromosome number in the microspore mother cell is 2n = 2 * 6 = 12.

5. The leaf tip cells of the plant species are somatic cells, and they are also diploid (2n). Therefore, the chromosome number in the leaf tip cells would be the same as the microspore mother cell, which is 12.

Hence, the correct answer is option **B) 12**.

The question says that 6 chromosomes are present in each of the 4 cells of the pollen tetrad and not in the leaf tip cells. So n= 6(pollen are haploid). In the leaf tip cells (since they are diploid), the chromosome number will be 2n = 12.