Question

Watermelons can have varying ploidies. Ploidy refers to the number of each chromosome present in a somatic cell. For example, most varieties are diploid that contains two copies of each chromosome, while some are tetraploid which contain four copies of each chromosome. Seedless varieties are triploid which have three copies of each chromosome that are present. Armed with the knowledge that seeds are plant embryos that have the potential to become a mature plant (and therefore are comparable to human embryos), why are triploid watermelon plants seedless (a.k.a. sterile), while diploid and tetraploid plants are capable of reproducing and producing seeds?

Answer 1

   In triploid plants three sets of chromosomes are present.Seeds are produced from the fertilized ovules.In the process of fertilisation male and female gametes are fused together to form zygote.So,for the process of fertilisation male gametes and female gametes are needed.Meiosis should occur in the formation of gametes.

But in triploids three sets of chromosomes are present.In meiosis pairing takes place and bivalents are formed.so,in triploids pairing does not takes place in third set of chromoses and meiosis does not occur and so gametes are not produced and fertilisation does not takes place.So,that is why triploids are infertile.

       So, in triploid fruits seeds are not produced due to lack of meiosis