How many chromosomes do diploid cells have?
Diploid cells do not have a set number of chromosomes that depends on the species. Diploid means that the chromosomes in the cell are in pairs ie two of each type. A human diploid cell has 46 chromosomes in 23 pairs.
Normally each member of the pair are identical in size, shape, the sequence of the genes that they carry the types of genes but not always the same allele of the gene
A haploid cell has only one of each type ie in humans the eggs and sperms are both haploid and contain only 23 chromosomes
Organisms normally go through a cycle of being haploid and then after fertilisation being diploid. In animals the diploid form is the mature form but in plants sometimes it is the haploid form. Perhaps you can find out which plants these are. The name of this cycle in plants is called ALTERNATION OF GENERATIONS
Also in some plants the cells are triploid Ie three of each type of chromosome. These tend to be very hardy plants and have often been produced commercially. You may like to see if you can find out an example of a triploid plant.