Endosperm of Pinus is haploid.

Explanation:
Endosperm is a nutritive tissue that is found in the seeds of angiosperms and gymnosperms. In Pinus, the endosperm is haploid. This is because the female gametophyte (megagametophyte) of Pinus is haploid, and the endosperm is formed by the fusion of a haploid male gametophyte (pollen tube) with the haploid female gametophyte. Therefore, the endosperm of Pinus is also haploid.

Pinus is a gymnosperm, which means that it produces seeds that are not enclosed in an ovary. The female cones of Pinus contain the ovules, which are the structures that eventually develop into the seeds. Each ovule contains a megagametophyte, which is the haploid female gametophyte. The male gametophyte (pollen grain) is carried by the wind to the female cone, where it lands on the ovule. The pollen grain then forms a pollen tube, which grows down into the ovule and releases two haploid sperm cells. One of the sperm cells fertilizes the egg cell, forming a diploid zygote, while the other sperm cell fuses with the haploid female gametophyte, forming the haploid endosperm.

In conclusion, the endosperm of Pinus is haploid because it is formed by the fusion of a haploid male gametophyte with a haploid female gametophyte.

In gymnosperms ploidy of endosperm is haploid... So as pinus belongs to gymnosperm, its endosperm ploidy is HAPLOID.