What is the nutritive tissue in the gymnosperm seed?

Haploid endosperm

Explanation:

Gymnosperms are seed-producing plants, but their seeds are naked (it is not within the ovary like in angiosperms).

Nutrient storage tissue in gymnosperms is called endosperm, but unlike angiosperms, it is haploid (angiosperms have triploid endosperm produced by double fertilization). Endosperm of the gymnosperms is formed from female's gametophyte. It is enveloped by peripheral endosperm that cotains grains of protein-aleurone.